Actual code - C vs. Python for a small problem

If you aren't much interested in writing software, this post is probably not for you. If you read the post without following the links to the example implementations, then I'm not sure what you are doing here, though you are certainly welcome to ask questions.

Recently on Quora.com someone asked to see C code to find the first 20 prime numbers. Seemed like an easy enough question, but the first guy who answered it, gave a C++-based pseudocode and some tips on how to convert that to C. That answer didn't make me happy. Heck, I figure if you're going to write in some other language, why not Python as a sort of testable pseudocode, but the question really needs that answer to then be re-stated in C.

So I sat down and banged out a Python program to find and print the first 20 prime numbers. That code is here: find20primes.py

I used a list to hold the list of primes. When the list grows to 20 items, I'm done. I start the list by telling it 2 is a prime number. I then only consider odd numbers as additional candidates. If the candidate is divisible by any of the prime numbers we've found so far, it is not a prime number. If the candidate isn't divisible by any of the prime numbers we've found so far, then the candidate is a prime number so we add it to our list of primes and, in ether case, add 2 to the candidate number to get the next candidate number to be tested. In C, we'll need a little more book keeping for the list, but since the max size of the list is bounded (20 items), things should translate from Python to C pretty easily. One trick that isn't entirely obvious is the use I made of Python's for...else control structure to catch the case of the for loop not exiting via break. We can paper that over with a goto in C, or you can add some flags

I was thinking that C has labeled break statements to let me do sort of the same thing as that for...else. But much to my chagrin, that's a feature of Java, not C. Oops. So, goto it is in my C translation of the program.

So I sat down with that Python listing open in one window and typed up find20primes.c That code is here: find20primes.c

I believe it is a straight-forward translation of the Python program into C. Of course, the C program is bigger in the sense of it has more lines of code. There are lines added to delimit the blocks and loops in the program, and lines added for variable declarations and lines added for the annoying book-keeping that C needs me to do where Python just handles those chores. I did run into some trouble where I didn't get the book keeping entirely correct the first time through. The program outputted 20 primes, but it started with 2, followed by 73, followed by 3, and it left out 71 at the end of the list. Huh? Turned out I was mistakenly incrementing primecnt before I'd used it to fill in the next slot in the primes array, so I skipped the primes[1] slot and just got 73 there by bad luck. Python would have told me about an uninitialized variable if there'd been a spot in the Python program for me to have committed that same kind of error.

Having finally gotten both programs working, conventional wisdom is that the C code should be much faster than the Python code. So I used the "time" command to see how the timings compare.

Using cygwin Python 2.7.8 on Windows 7 on a PC with an i5 processor and 8GB of RAM,

$ time python find20primes.py

[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71]

real    0m0.136s
user    0m0.000s
sys     0m0.062s

Using cygwin cc 4.8.3 on that same Windows 7 PC:

$ time cc find20primes.c

real    0m0.238s
user    0m0.045s
sys     0m0.185s

$ time ./a.exe
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71

real    0m0.064s
user    0m0.015s
sys     0m0.015s

The execution time for the compiled C program was way less than the total time for the Python run, but if you add in the compile time for the C program, Python comes out ahead. Your mileage may vary.

By the way, if I throw in a -O option ("optimize the generated code") on the cc command, it further slows the compile down, while the run time is about the same.

$ time cc -O find20primes.c

real    0m0.336s
user    0m0.031s
sys     0m0.185s

$ time ./a.exe
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71

real    0m0.086s
user    0m0.000s
sys     0m0.015s

(the "real" elapsed time varies a lot from run to run. These run times are so short the variability makes it hard to make fair comparisons in races between the programs). I suspect that the real time is dominated by the console I/O to print the results, so optimizing the details of the loops isn't going to do much improving of things.

Now to make things more interesting, suppose I wanted to pass in as a command line argument the number of primes to be found. So long as the primes are still in the range of ints that only needs a malloc of the array in C but if the program is ever asked to get up into really big primes, the Python code will keep on chugging while the C code will need substantial rework to pull in an arbitrary precision integer library module. This blog article is already long enough, so I'll leave that generalization to "findNprimes" up to you. How big does N have to be to break the C code's use of ints? I suppose that with relatively minor surgery, you could convert over to use of long ints (or if your compiler supports them, to long long ints) in the C program. Looking into it lightly, it appears that the cc included with Cygwin supports long long ints. The format strings will need adjusting. Use %lld instead of %d.

If you've feeling anxious to try further experiments, see how pypy does in handling the find20primes.py program. That'll probably be more interesting with findNprimes.py with a really big value for N.

The moral to the story is that C may not be the best choice of programming language for this kind of problem.

Did you enjoy this article or was it too technical? Please add a comment down below so I know what you think about this sort of writing.

Getting more familiar with Python Classes and Objects.

If you've been following this blog, you're aware that I feel unprepared to make good use of the Object Oriented Programming facilities of the Python programming language. Python is kind enough to allow programming in non-OOP styles, but Python's OOP features keep glaring at me, reminding me of what I don't comfortably know.

I posted a question on Quora.com asking for real world examples of multiple inheritance being used in Python programs. I was disappointed about how few answers came back. That dearth of response left me with the suspicion that I'm not the only person around who isn't completely comfortable with multiple inheritance. http://www.quora.com/What-is-a-real-world-example-of-the-use-of-multiple-inheritance-in-Python. Looking around at other multiple inheritance questions on Quora (http://www.quora.com/Why-is-there-multiple-inheritance-in-C++-but-not-in-Java), I see some reason to suspect that super serious application of OOP is just going to need more time to sink into the heads of the majority of developers. So, I'll continue to watch and learn, but will try to remember to adhere to the KISS principle to the greatest extent possible.

Additional Lessons

1. This 40 minute video from Ray Hettinger (The Art of Subclassing) explains how Python classes differ from classes in other languages. Ray tries to reshape people's thinking here, so if you aren't already deeply steeped in OOP lore, you may feel he's dwelling on the obvious. He may give you some ideas of appropriate uses of inheritance in Python objects.

   
   

2. Ray mentions this 2nd talk in his video. This 2nd talk was the next talk after his at Pycon 2012. "Stop Writing Classes", Jack Diederich, 28 minutes. Basically, that video asserts that my own example so far of writing a class for a Python program is not very good. The clue: My example class had only __init__ and one other method. I could have written it as a simple function and used the partial function from the library functools module to handle the initialization.

Further Reading

I have 3 previous blog articles on OOP in Python.

In Creeping up on OOP in Python - Part 1 I described a use of an object-oriented library module, pyparsing, to solve a Project Euler problem.

In Creeping up on OOP in Python - Part 2 I reworked my solution to add a simple class of my own. I was happy that introducing that class made the code cleaner to read. But if you watched the "Stop Writing Classes" video given up above in this blog article, you'll probably notice that my class is an example of exactly what they say you shouldn't do.What can I say? I'm still learning this stuff.

The 3rd in my Creeping up on OOP in Python" series was a bit different from the first 2. It explored an academic question about multiple inheritance. It is exactly the kind of A, B, C example that Ray mentions avoiding in his talk. Creeping up on OOP in Python - Part 3. I haven't forgotten my promise of a Part 4 as soon as I have a practical example of multiple inheritance to substitute for A, B, C and D in that academic question. But so far, there is no Part 4.

Ray mentions "the gang of 4". If you aren't familiar with them, here's a reference for you to pursue: http://en.wikipedia.org/wiki/Design_Patterns. And he mentions "Uncle Bob". I also mentioned Uncle Bob, with some links here: SOLID software design.

Know more about this OOP stuff then I do? Well, don't keep the info to yourself. Please post a comment with a link or example to help me learn more. Have you found a particularly relevant MOOC that you'd suggest?

Home Networking with FIOS - Don't cross the streams.

As you may remember from my article Adventures in Home Networking, we very badly wanted to get out of using Cablevision. They'd agreed to a price to provide service to our home, but then consistently billed for significantly more per month then the agreed-to price. We got the NY Public Service Commisssion involved, but every month's bill turned into a new argument with Cablevision with the PSC insisting that they accept the payment of the agreed-to amount. Cablevision would accept the payment and leave the service connected, but rebilled the unpaid difference the next month as an amount past due. There were some months they'd insist they hadn't received the payment and we'd have to get a 3-way call between the bank, Cablevision and the PSC to establish that Cablevision indeed had collected the previous month's money from the account and then mis-placed it.

We got tired of that monthly argument, and looked for alternatives. The hard part was finding Internet service. Given Internet, it is easy to get phone service (e.g. Vonage or MagicJack), and there are non-cable alternatives to television service (e.g. DIRECT-TV and Dish satellite service). We had tried Hughes Satellite Data service as an Intenet Service Provider, but found it to be expensive (limited data transfer allowed per month), high latency and noticeably prone to dropping packets. We concluded that Hughes would not be a good substitute as an Internet Service Provider for our home. As I described in that January, 2014 article, we also worked out how to put our home on AT&T's Mifi service (cellular LTE data service). The problem we had with it was again limited data transfer allowed per month, $10/GB for overages. It was fast enough, and seems reliable enough, but at $52/month base, is somewhat expensive. It also had the irresistible temptation to take the access point along when traveling out of the house, but that would leave the house without service while the Mifi was on the road. In the end, we kept the Mifi box and grudgingly pay the $52/month just for the convenience of having Internet access while away from the house. (Well, the other rationalization of the $52/month is that it ensures that I have Internet service even if my home's ISP is out of commission. It's not just that I'm addicted to blogging. I use the Internet for work too). Cablevision, of course, sings a song about having Wifi hot spots in many places. But our experience with those is that often the signal is too weak to be usable. e.g. there is no Cablevision Wifi at our house. If I go down the block, there is Cablevision Wifi in the nearby park. At our local supermarket, there is a signal if you walk out to the sidewalk near the street, but inside the store you are out of reach. Similarly, at some of my doctor's offices, there is a signal out at the street, but inside at the reception desk, the signal isn't strong enough to be reliable. The Mifi box is more secure (uses your own WEP password for encrypted Wifi) then Cablevision's unencrypted Wifi and AT&T Mifi seems to work well even inside low-rise buildings such as are common here in the suburbs.

So, after running out of alternatives, we decided that we'd drop Cablevision and go with Verizon FIOS even though it wasn't going to save us any money. The one advantage seems to be that FIOS includes Jimmy Swaggart's Son Life Network which my wife enjoys. If you want to hear a disgraced minister sing hymns, maybe you'll like it too. It's probably easier to enjoy if you simply reject those repeated charges of cavorting with prostitutes as "obviously" false (New Orleans and Los Angeles). If I was providing a sound track to go with this paragraph, I think I'd opt for the Beach Boys "California Girls". I'm just not creative enough to produce a mix of that and some suitably religious ditty. Not that it is in any way a religious ditty, but how come it seems so rare that the radio ever pairs up California Girls with "Back in the USSR"?

It probably helped minimize any shock from the bill that the price negotiation with FIOS was done by me, not my wife, so we came away with more realistic expectations of what the bill was really going to be. Verizon loves to tack unpleasant surprises onto the bill. e.g. unless you ask, the prices they quote don't include things like $27.98 "Taxes, Governmental Surcharges and Fees" and $25.55 "Verizon Surcharges and Other Charges", but the bill includes those. The first 3 months of service also carry an extra $49.99/month "Activation Fee". There were still surprises to be found by careful inspection of the bill. My wife is flummoxed by the notion of keeping an address book organized by name so you can find people's contact information. Her habit is to write the info on scrap paper, which she then loses, so she repeatedly calls 411 to get the number again. In one month that was 30 calls to 411 at $2.49/call. I keep pleading with her to learn how to use Google, but that just turns into my having to do it for her and getting peeved when I recognize that I'm looking up the same information as I'd given to her before. I wrote some of the contacts into a bright orange address book and she acts surprised every time I show her that she already had the information there.

Video problems with FIOS

The other bad surprise, in our 2nd month bill, was $156.03 for a service call we'd placed with Verizon. Multi-room DVR playback to rooms remote from the actual DVR was unreliable. They sent a guy out to trouble shoot the problem, but he didn't fix it and he didn't write it up as a Verizon problem, so they billed us for an hour of labor. I protested and they did deduct the labor and the tax on the labor from that month's bill. We found more ways to demonstrate the video problem and called for yet another repair visit. The 2nd repair guy was unable to fix the problem too, but we learned a little from chatting with the guy while he was here. In the world of Cablevision, so far as I can discern, data service and television service are quite separate, sharing the same physical cable but traveling in separate channels. But with FIOS, each television set-top box gets an IP address. Some television services depend on being able to talk via the Internet router to get video to the set top boxes. Remarkably, the Verizon service folks don't have any kind of protocol analyzer or even a simple bit-error-rate monitor to give them visibility into what is doing on the home network.

The first repairman's visit wasn't without value. He noticed that our HP printer was assigned IP address 192.168.1.100. This had been our household's long standing convention, so any PC could know how to reach the printer without needing DNS or something complicated to find it. But 192.168.1.100 thru 192.168.1.150 are "reserved" by Verizon for use by their set-top boxes. Oops. So I reassigned the printer to be 192.168.1.99 and adjusted the configurations of each of our PC's accordingly. This did make access to the printer more dependable, without having to fuss with power cycling it after a period of disuse, which had been the state of things since we switched to FIOS. But it didn't get rid of the problem with multi-room DVR playback. We'd also found that the FIOS video tutorials, which are short video-on-demand clips from some central server of theirs also had similar problems of occasional stalls and pixelization in playback. The 2nd repairman saw the problem happening and after examining the router configuration opined that we just had too many devices on our home network for the level of service we'd subscribed to. (Our service is their 50/25 speed. For more money, we can have more bandwidth, but since I'd seen the whole house [excluding FIOS video, of course] doing fine with LTE cellular data service via AT&T Mifi, I didn't think that was a good explanation of what was wrong). To the fellow's credit, he did take the time to disconnect portions of our home network from the router until the problem went away. At that point I had to accept that the problem somehow lay with our home network, though further trial and error would be needed to find the real problem.

So, at this point we had as our only instrumentation, that when the problem wasn't present, we could watch Verizon FIOS training videos without a problem, and that when the problem was present, that a few minutes of playing the training video would result in pixelization and stalled playback. I set about through trial and error to find which of the wires he disconnected mattered. My first suspect was the long cat-5 cable to the router in the garage apartment. The dog had occasionally chewed on that cable and we'd taped it up and it seemed to work well enough, but I certainly wasn't prepared to swear the cable still met all cat-5 specifications. I plugged it back in to the FIOS router and the picture stayed clear, so it wasn't that cable. Only other cat-5 cable I knew about was one that runs through the attic to get to the rear bedroom where the printer resides. Puzzler was that while doing my wall crawl to reconnect things, I found 2 cables running up to the attic. What was the additional cable? Took some more crawling in the rear bedroom to figure it out. Turns out we had 2 cat-5 cables running from the front bedroom to the rear bedroom. Once upon a time, one was for the PC in the rear bedroom and the other was for the printer, but now the PC and the printer are connected to an inexpensive 100-base-T switch so the 2nd cat-5 cable to the room is unneeded. Mistakenly, both cables were plugged into the Verizon router in the front bedroom, and both were plugged into the switch in the rear bedroom. That's just plain wrong. I don't think it ever bothered the Linksys router that used to be in the front bedroom, but the FIOS router showed video playback problems unless you disconnected the erroneous 2nd cable from the router to that 100-base-T switch. Oops. Mixing video playback in with the mostly non-realtime Internet data traffic apparently got fouled up by the wiring mistake. What a pity that Verizon didn't have appropriate tools for their field support people to really find this problem. Anyhow, now that the extra wire is disconnected, things have been much better with the multi-room DVR.

More FIOS Woes - You Own the House Wiring

But we did have other FIOS problems. Cablevision ran a coax cable to a "cable modem" in the front bedroom. There were 2 phone jacks on the cable modem that provided our house phone line and our fax phone line. FIOS doesn't work that way. FIOS mounted a big white box on the outside of the house and ran the fiber to that box. They also installed a large UPS on the wall inside the house and ran power from the UPS to the white box on the outside wall. They then re-used Cablevision's coax cables to connect a coax cable from the FIOS box to the various TV's via a splitter box on the outside wall just below the FIOS box. There is no "cable modem" box as we had with Cablevision, but the Verizon Internet router has a coax connection of its own that it uses to talk to the FIOS network, including the settop boxes. The outside FIOS box also has about 8 phone jacks in it. So, Verizon ran 2 phone lines from those jacks to ancient NY Telephone demarc boxes on the outside wall, to tie the 2 phone lines to the ancient inside house wiring. The deal as I understood it was that as long as Verizon provided dial tone at the demarcation box, that any remaining phone problem was a "house wiring" problem and is only covered by Verizon if you pay them a ridiculous monthly surcharge.

After a particularly rainy Spring night here, the Fax machine lost it's dial tone. I know I had a corded phone around the house, but darn if I could find it. So we traipsed off to Walmart where for $6 I bought a nearly feature-less corded phone. It looks sort of like an old Trimline phone, but I found the base is just a place to set down the handset. The wire from the walljack runs straight through the base and into the handset. The touchtone keypad, ringer, etc. are all in the handset.

Armed with my corded phone, I could verify that things were funky at the demarc boxes. For starters, the boxes weren't labeled with current phone numbers, but worse, the installer had hacked around some problem in at least one box so the modular jack for test access wasn't working at all. So we arranged for a service visit for the coming Monday for Verizon to look at lack of a dial tone on our 2nd line.

More FIOS Woes - the Fragility of the Fiber from the Pole to the House

But Friday, before we ever got to that Monday service visit, something happened to our FIOS service. We lost everything - TV, phone and Internet. Verizon, contacted via cell phone, agreed to send a repair guy out on Saturday. The FIOS box has an LED in it to tell the repairman if the fiber is delivering a signal to the FIOS box. It immediately told the repairman that there was no signal. Alas, he arrived on a truck with ladders, but the fiber drop cable to our house is connected to the distribution fiber mid-span, between 2 telephone poles, so the junction is only accessible with a "cherry picker" truck.

From the ground, something looked dangly at that junction, but nothing was actually laying on the ground. So we waited for them to dispatch a cherry picker truck with a buddy of the repairman's to help him. Once that arrived, they determined that something had severed the junction from the distribution fiber to the drop fiber. So they had to replace the drop fiber. This was surprising to me as this is now my 4th drop fiber in the short times I've had FIOS service. The first drop fiber was installed much like this one, but drooped a little low over the street. One day a large cement mixer truck drove down our street and managed to knock down our fiber and the one to the house next door too. So Verizon sent a repair crew to replace the fibers to our homes. They sent 2 trucks, one for each house, but they decided to work together. The lady with the ladders worked the house end of the job and the guy with the cherry picker truck worked out by the poles on the street. I was impressed with the result. At the house, the fiber came off a board sticking up from the peak of the house's roof. It then flew super high across the street direct to the pole at the corner. It was well clear of any trees and certainly too high to ever get struck by a passing truck on the street. Beautiful looking installation. Alas, it was no match to Hurricane Sandy. Fiber #2 ended up on my lawn after Sandy passed through. Annoyingly, Cablevision's coax to our home survived the storm just fine. Since we were off of FIOS by the time of Sandy, we only had Verizon out for a non-emergency clean-up call to get their fiber off of my lawn. Of course, when we resumed FIOS service this Spring, the installer had been told this was a simple re-connect of a previous customer. Lots more to the job than he'd expected. He installed drop-fiber #3. It ran from the board at the roof peak through the trees to the mid-span point where drop fiber #1 had been attached to the distribution plant. I think the board at the peak added enough height that #3 was going to be safe from passing trucks. But the community center opened up and installed a driveway under the distribution span. The guy who installed drop fiber #4, opined that maybe a school bus turning into the community center disturbed the distribution fiber enough to jostle our drop-cable into failing. He put in a request for the outside plant people to come around to raise the distribution cable a smidge where it crosses the driveway, but I didn't see them come to do that. We'll just have to wait and see how long drop fiber #4 lasts.

The Internet tells me that I'm not the only FIOS customer having repeated service calls for fiber repair.Hungry Ants Knock Out FIOS Service ... Again. I can only assume that these problems are evidence that fiber to the home is new technology and there will be some time before they gain enough experience to work out the Field Engineering kinks to make this reliable. The price of repeatedly replacing the drop cable presumably is enough motivation to encourage Verizon to eventually get it right. The Mifi box and my cell phone at least make it tolerable when we have an occasional day of no FIOS service. Of course, there is the annoying whining sound of my wife complaining when she misses an episode of General Hospital, but so it goes.

When the fiber connection to the outside FIOS box was restored, I asked the Saturday repairman to look at the problem of no dial tone to our Fax machine. He advised that the white FIOS box is now the point of demarcation. He verified that there was dial tone available on lines 1 & 2 at the FIOS box, but that means the crappy old NY Telephone demarc boxes are now part of the house wiring that is my responsibility.

So I looked and found on the house a disused demarc box that then had a phone line running back to the rear bedroom. My wife reminded me that some years ago her Aunt Dolly had lived in that rear bedroom and had a phone line of her own. Aunt Dolly has long since moved out of here and is now deceased. We attended her funeral this Spring. So, I snipped the wire off the old NY Telephone demarc box and ran it into line #2 inside the FIOS box. I added a new modular jack to the spot where that line comes into the rear bedroom and then ran a phone cable from that modular jack to the Fax machine. Voila, the Fax machine has dial tone again and we're using less of the ancient house wiring then we'd been using before.

The future of FIOS??

There's some evidence that Verizon is unhappy with their return on investment in converting their distribution network from copper to fiber. e.g. Wall Street Journal: Verizon to End Rollout of FIOS and DSL Reports: Verizon Again Confirms No Future FIOS Expansion. Will the day come when they try to close down their fiber business? Seems unlikely to me, but we do live in "interesting" times.

I've got to wonder where are the regulators in the process of Verizon making non-aggression pacts with the cable television companies. e.g. Verizon’s Anti-Aggression Treaty With Big Cable May Be the End of FiOS. I really think it is better for the economy when the cable companies have at least one competitor in every neighborhood, preferably one with a different technology and the fire in the belly to want to rewire the country to fiber. Verizon once upon a time had that fire, but now, like AT&T, seem to have lost their sense of direction. Too bad!

Cross the Streams?

I keep forgetting that Ghostbusters was an increasingly long time ago (1984). When our FIOS video problems turned out to be from the mixing of Internet traffic and FIOS video packets, Egon's warning about the dangers of "crossing the streams" immediately sprung to my mind. If you haven't seen Ghostbusters recently, you really should rush out and rent it. But thanks to Youtube, we can give you the relevant clips from the movie. First, the scene where Egon warns "Don't cross the streams!" And, second, the climatic scene where the team makes a slight change of plan and deliberately crosses the streams. A bit of a spoiler, but you still really should see the whole movie.

Message In a Bottle

If you know someone who maybe knows someone in Verizon who'd be in a position to officially react to this note, please pass along the link to this article. I'd be delighted if my woes actually got to the ears of someone who could be properly embarrassed at the lack of network diagnostic equipment in the hands of the Verizon field support staff, or the need for improved field engineering of drop fiber installation and could maybe nudge Verizon in the direction of actually doing something about it.

How Secure is Your part of the Internet?

Problems with Internet security have been much in the news lately as our homes have been getting more and more connected to the Internet with the growth of the Internet of Things. Please note that I'm one of those people who make a distinction between the terms hacker and cracker.

Image borrowed, without permission, from http://ariefuchulz.blogspot.com/2012/02/hacker-vs-cracker.html, apparently the blog of Arief ucHulz.

A specific recent report that caught my eye:

Until We Fix Our Connected Homes, Crackers Will Keep Screaming At Babies

The simple conclusions offered by that article is that if your home is connected to the Internet, to be secure you should:

1. Take care to set secure passwords on all your devices. Leaving the manufacturer's defaults are just asking for intruders to come by.
2. Register your devices with their manufacturer so the manufacturer can get in touch with you about security updates. Unsaid is that such registration will open up your e-mail inbox to a likely flood of promotional e-mail (a.k.a. spam).
3. Keep your device's firmware/software up to date. Unsaid is that not all devices can accommodate updates, and not all manufacturers put much effort into providing updates on old products. Maybe the manufacturer no longer makes that product. Maybe the manufacturer no longer supports that product. Maybe the manufacturer has gone out of business.

The article mentioned briefly that the homeowner had "secured" their home's router that connected their home devices to the Internet. I wished that article had explored that statement in a little more depth. "Securing" a router is quite an essay topic in itself. If you have a router connecting your home to the Internet, please stop and consider how secure is it?

1. Have you set a secure password so only you have administrator access to your router?
2. Assuming your router provides you with Wifi (wireless Internet connectivity), have you configured the router to have a serious, non-default password protecting your Wifi network from intruders? There's more than one choice available for Wifi Encryption. Which Wifi encryption option have you picked? If you picked WEP, you'd be well-advised to switch to WPA2. There's freely available software that anyone with a notebook PC within range of your Wifi signal can run (e.g. Automatically crack Wifi with only 30 seconds work. I offer the link as an example, but haven't actually tried to follow that page's instructions myself). The software needs only to listen to your WEP-encrypted traffic for a short time and it will then reveal what the password is that your Wifi network is using. In other words, WEP encryption isn't at all secure if faced with anyone who wants to intrude on your wireless network.
3. And now we get to the hard question: What is your router configured to do with incoming traffic from the Internet? If the router rejects all packets coming from the outside world, it isn't going to be much use. If you use your browser to visit a web page, you send out packets requesting the web page and web page's server sends back packets that tell your browser what the web page says. If you configured your router to reject those outside packets, you'd likely be most unhappy with your router's behavior.

   Most routers will let you accept only traffic that comes in reply to packets that you sent out to the Internet and that covers most cases. But there are ugly cases where, for example, you initiate an FTP connection and the remote FTP server replies using a different port than the one that you used to initiate the connection. If your router is configured to reject packets that don't look like replies to traffic that you initiated, you're likely going to have trouble doing FTP file transfers.

   A stickier problem is do you ever want to access your home Internet from elsewhere? For example, some folks have home security systems (or perhaps a baby monitor) and want to be able to check in on it from their travel PC while away from home. Almost certainly that requires the router to be configured to allow outside Internet traffic, traffic that isn't in reply to inside-traffic, to come into your home. How secure is your home network to outside traffic coming from a wannabe intruder?

You can try to secure your home, device by device.

Consider, for example, the HP Inkjet printer in my home, an HP 7410 all-in-one printer/scanner/copier with built in Wifi capability. When we first set it up, we put it in a room that didn't have wired ethernet available so we configured it to use that built in wireless capability. Worked wonderfully. Then as I became aware of how easy it was to break WEP encryption, I decided to reconfigure our home router to use WPA2 encryption. Surprise! The HP 7410 printer's built in Wifi support only knew how to handle WEP, not WPA2. I looked into how to upgrade the firmware of the printer, but so far as I can see, the firmware of that printer is permanent, not updateable. Now, for all I know, I could go out and get a new printer that has WPA2 support, and probably has other advantages like, perhaps a faster printer speed and just maybe less expensive ink. (well, I can dream, can't I?). But this printer still works fine, so I'd feel guilty throwing it away just because it doesn't support secure Wifi. So, instead, I grumbled and bought a long Cat-5 cable so I could have a wired ethernet connection from the router to the room with the printer. For less than $10 we also added a wired 8-port 100-base-T ethernet "switch" to that room so we could easily connect all the devices in that room to the wired network. I talked a bit more about my home network back in January. See: Adventures in Home Networking

Barry Shein, one of the early pioneers of the Internet as we know it today, recently posted this note to Facebook:

Internet security is so bad because it was never particularly designed to be secure.

I've been on the net since the 1970s, involved in its technology and politics. I don't remember anyone ever saying or promising "and it has to be secure, right?" until the 1990s.

What happened is in the 1990s a bunch of people figured out how to make A LOT OF MONEY off the net, or save a lot of money, same thing.

But most of their plans required the net to be secure.

So security became a BIG ISSUE. Ok.

It's like coming to a river in your car and thinking hmm, maybe I can just slap some wings on this thing and fly across.

The power of the net is that it enables everyone to share information very easily and very widely.

Now, re-read that sentence with security in mind.

If you aren't uncomfortable yet, I've got more for you to read. Shortly before Barry posted that cautionary note on Facebook quoted up above, he posted on Facebook:

If you try to engage me in a conversation about computer and network security and I don't know for a fact you're an expert I'm going to check whether you read this article. And if you haven't I will politely ice you out.

Everything is Broken

Now there are many different opinions as to what you should do. I don't have the energy or time this morning to track down exact references for what Richard Stallman suggests, but at the risk of mis-reporting what he has in mind, I'll tell you what I think he has said:

1. Don't trust software that you can't examine and modify on your own.
2. Don't allow untrusted 3rd parties to have control of the software on your devices. e.g. allowing auto-updates of your PC by Microsoft, Apple,Adobe, Oracle (Java) and Google (Chrome, Android) is imprudent. Even if you trusted the software after careful evaluation of it yesterday, how do you even know what the software you are running today will do?

The trouble with "trust no one!" is that you are cutting yourself off from much of the world. And even if you insist on only running software where you can examine the source code, you likely are only fooling yourself. There's too much software in layers and layers for you to have any hope of being able to detect security problems. Security problems can be quite subtle and hard to recognize. Consider for example the recent brouhaha over the security of OpenSSL in its Debian implementation. The source code was all open and freely available, but it took years for anyone to notice that a security bug had been introduced into the code. The xkcd comic had some good jibes at the security of other open-source systems: http://xkcd.com/424/.

I'll go so far as to suggest that if you refuse to allow auto-update of the software on your devices, you are doomed to never being able to keep anywhere close to current on the latest security updates. There are just too many of them and they come out too often to try to track them by hand. And you'll have a hard time convincing me that the reason you insist on tracking them by hand is you want to research what each one is about before you install it. Good luck with that!

And then there's the problem of web-services like dropbox, gmail, Google drive, Google docs, Facebook, ... Pearltrees, and the list goes on. Generally, you don't get to see the source code that implements those services, and often you have no control over when that service implementation is updated. At some point you have to decide which suppliers you are willing to trust. Stallman will tell you that Facebook surely doesn't belong on that trusted list. My wife has no Facebook account and insists that no one should share her picture or name there. Her children don't buy into that "no Facebook" policy because it would cut them off from keeping in touch with their friends.

I could go on and on, suggesting that you look into "Virtual Private Networks" for securely allowing connections from the outside Internet into your home. But you pretty much have to trust somebody to do the right things to protect you.

But who can you trust? 12 biggest baddest [known] software backdoors of all time. "all time" in that title underestimates what the future could hold. And the article isn't very keen to point out that it is only talking about known backdoors. Goodness knows what unknown backdoors are lurking out there.

In closing, here's a 17 minute TED talk that defends "hackers" as a necessary part of the Internet eco-system. The talk doesn't draw a distinction between hackers and crackers, but so it goes.

Hackers: The Internet's Immune System.

Comparative Programming Languages

Here are a couple of videos from luminaries in the software world that I believe are worth the time to watch.

First is Rob Pike explaining why he created the Go programming language.

OSCON 2010: Rob Pike, "Public Static Void"

That's a short talk of 12.5 minutes.

Far longer at an hour is this talk by "Uncle Bob" explaining what killed Smalltalk and how the same factors could kill Ruby too.

RailsConf 09: Robert Martin, "What Killed Smalltalk Could Kill Ruby too"

Note, that when Bob finishes with the last of his note cards, the talk is NOT over. I urge you to stay in your seat until the end of the video. Patience!

Now to be fair, I'll have to admit that I haven't programmed in Ruby nor Go nor used Rails and I'll even confess to limited experience with Test Driven Development (TDD), but I think I've got to get one of those green wristbands for myself. So if your reaction to the prospect of watching these videos is "Ain't nobody got time for that!", well, as a consolation prize, I'll give you a link to a related, but short to read XKCD comic:

How Standards Proliferate

Python Generators

Background

Back in May, 2013, I posted "Cheap, but not Free, Modular Code has a Price". In that blog article I compared the performance of my solution of Project Euler problem 14 to the performance of Nico Ekkart's solution of that same problem. As I explained in that article last May, Project Euler's guidance on performance is that a solution should be able to complete on a typical PC in less than a minute. My initial solution ran well over a minute and I applied a cache to speed my program up. Once I'd gotten it down below the one minute limit, I had concluded "good enough" and went on to other problems. But Nico honed his solution a little tighter and outperformed my program by a factor of 4.

Looks to me that we had basically the same solution, but his was more of an in-line implementation, while I used a Python generator to produce the sequences of numbers the processing of which is the heart of problem 14. I concluded that the Python structuring facilities like generators do add overhead but I opined that the added clarity of packaging the sequence generation as a "generator" made the overhead worthwhile. Nico's code for his cache was so little code that I didn't really defend my use of a Python "class" for my cache implementation. Some further experiments with the code to determine how much of my extra overhead came from the generator vs. how much came from my cache implementation might be interesting. I've posted the source code and invite you to experiment and share your findings.

But that isn't what I came here to talk about today

This blog post today is aimed at expanding your knowledge of Python Generators and share with you a neat trick that I've recently learned: a generator of dictionaries.

Python Dictionaries

Back in January, 2013, I posted "Dictionary Implementation". In that article I pointed to where the Udacity CS101 MOOC introduces Python dictionaries and pointed to further places to look to learn how Python implements dictionaries, hash tables. If you aren't comfortable with Python's notion of a dictionary, I'll sum it up as an easy to use collection of name-value pairs, much like an array is an easy to use collection of subscript-value pairs.

Given an integer value as a subscript into an array, you can easily ask for the value associated with that subscript. (In Python such an array is called a "list". But if you have a dictionary of name-value pairs, in Python it is easy to ask for the value associated with a name. e.g. What value is associated with "eggplant", where "eggplant" in this example is a possible "name" entry in the dictionary. If this is all still mysterious to you, my suggestion is to dig for more info on the web. Google search is your friend. A Google search for:

python dictionary

turned up more than 5,000,000 web pages today and Google looks to have done a decent job of sorting the most helpful ones to the front of the search results.

Or perhaps you should work your way through Udacity CS101 to learn this concept of dictionaries and more.

Python Generators

But as I already said, the topic of my blog post today is Python Generators. Rather than take the time and trouble to create a fresh new tutorial about Python Generators, I'll pause here to provide a link to an article from April 2013 from Jeff Knupp: "Improve your Python: 'Yield' and Generators Explained". That article resonated with me as written in an easy to understand way. It's about 19 screens long, so it isn't a quick read, but you can get back to Facebook and YouTube later.

Knupp's article should certainly get you to the point of being comfortable with my Project Euler problem 14 generator. My generator is very vanilla, just conjuring up a sequence of numbers. The one tricky aspect is my program often doesn't pursue the sequence to the end, but sometimes decides it needs to see a new sequence. I was a little nervous when I did it that way, but now understand that Python doesn't mind dangling generators like that, and even should know enough to be able to garbage collect their saved state, if memory gets tight and it is clear that there's no way the program could get back into that old sequence. Powerful stuff and a feature unlike anything available available in C, Fortran, Basic or Cobol to name 4 examples of older more traditional programming languages.

But Wait! There's more!

If you've read this far but are yawning, thinking that hardly ever do you, yourself, have occasion to use complex logic to generate a sequence of numbers in the programs that you write, well hang on and see what else generators are good for.

Igor Vasilcovsky recently pointed out to me an interesting tutorial from David Beazley about generators. The meat is the slide deck under the presentation link on that page. Even with 2 slides to a page, that slide set runs to 79 pages so it probably is too much to absorb in one sitting. So try to work through it in several sessions. Here's my summary of the key elements I think you should get from wading through that presentation:

1. A generator can return any kind of Python object. That is, it isn't limited to returning the numbers of a sequence. If you paid close attention to my Pythonic Python from July, 2013, you may remember that one of the points I made there was that Python functions can return large complex objects, not limited to just a number or just a pointer. Better still, Python takes care of the book keeping to automatically garbage collect the returned object if you are no longer using it.

   Beazley has examples with a generator returning strings (lines from log files), and then takes an unexpected turn to have the generator parse the strings into values and stash the values into a dictionary with a name for each value and then return the resulting dictionary as the generator's output. (A dictionary per line of the log file!) My initial reaction to that was to be horrified at the overhead, but if you think about it, looking up a name in a dictionary is quite central to Python's run time modus operandi, so dictionary objects being generated is perhaps more general than generating some more specific Python class object, and looking up values by name is pretty much the same as using a name of a member of a class object to get to a value in the class object. So given that Python is able to get decent performance from run-time interpretive execution, generating dictionaries is a lot more sensible then my initial gut reaction took it to be.

2. A generator is just Python software so it can do anything that any Python software might want to do to provide the next value in the sequence. It can compute the next value using a formula, or it could access a file to learn the next value. It is even able to make use of another generator to get an input sequence that it manipulates and passes along. So generators can be chained together into long pipelines.
3. If your program is basically about iterative processing of a series of stuff, then chaining together pipelines of generators can fundamentally shape a clean structure for your program and with a little practice you'll soon have a collection of useful reusable filters that you can use to construct future programs that you haven't even thought of yet. Share them with your friends. If you own the code, consider making it (and it's documentation) GPL licensed and freely shared on Github or some other such public place.

I'm seeing hints on the Internet that future Python releases will have even more use of generators. e.g. standard approaches built in to the language to process streams of events. e.g. Brett Cannon's 40 minute talk: "Python 3.3: Trust me, it is better than 2.7". He foreshadows a Guido Van Rossum talk about Python 3.4 scheduled for that same conference. If you can find a link to a video of Guido's talk about 3.4 and new roles for generators, please share it in the comments section here.

Adventures in Home Networking

I have a home network that is just a little complicated. I made some changes to it this weekend and thought I should share the story with you.

Initially, we have Optimum Online Cable Internet Service. They'd promised a price for the bundle of telephone lines, Internet service and television service to my wife, but then the monthly bill greatly exceeded the promised price. She dragged in the state Public Utilities Commission and negotiated the price back to the original promise, but each month since them, paying the bill has been a multi-hour phone call where Cablevision asks for the billed amount and my wife reminds them of the agreed to amount with the PUC. We do still have cable TV and what not here, but she's getting tired of the monthly ritual and wants to get out of using Cablevision.

Replacing the TV portion of their service looks easy. We can just get DISH or DIRECT-TV satellite TV. We had it before but were unhappy that in heavy rain storms, the satellite signal seemed to get frequently interrupted. And the satellite TV companies, despite their commercials, don't seem to have any Internet service to seriously offer in our area. We'd made do with DSL service, but the bandwidth that we wanted just wasn't there.

We tried Verizon FIOS, but the monthly bill was higher than we wanted and the service was less reliable then we'd like. Seems that the technicians just haven't quite perfected running the fiber drop cables from the pole to the house. One random day a big cement truck traveling down our street took out our fiber and the one to the house next door too. Getting that fixed took many days longer than we'd have liked. We got fed up with the high bills and switched to Cablevision service. Good thing too, as the Verizon fiber drop cable came down again in Hurricane Sandy shortly thereafter. Cablevision's drop cable survived that storm, though the service was out for quite a few days while the area was without electricity.

So, the hard part for replacing Cablevision here seems to be Internet service. I really didn't want to go back to DSL or to FIOS. My wife keeps wishing that some other cable company would start to serve our area in competition with Cablevision, but it seems like that isn't going to happen any time soon. We tried Hughes satellite internet service. "Try it and cancel within the first 30 days with no obligation if you don't like it". We didn't like it. The packet loss rate was uncomfortably high (so that often when I'd download something, I'd end up having to repeat the download until I'd get a complete file. Now maybe with some tweaking of retry allowances, we might have been able to get the TCP/IP to work well enough over the lossy link, but the apparently unfixable part of the service was the high latency. My wife's son is a huge X-box fan and likes to play shooting games like World Of Warcraft against Internet-connected opponents. Alas, with the high latency of the satellite, you're dead before your opponent's gamebox ever even hears that you pulled the trigger. We certainly didn't need 30 days to decide the satellite service wasn't a good match to our needs. So we cancelled and returned their equipment to them.

My one remaining idea was that maybe we could make do with a Mifi hot spot from a cellular company. There are 2 gotchas that worry me. One is that not everything in our house is on Wifi. The HP 7410 printer, for example, can't do WPA2 encryption on its wireless port, just WEP and WEP encryption is hardly any more secure than no encryption at all. So we're using a wired ethernet port on the printer. I rigged the DHCP in the router so the printer always gets a fixed IP address. That made it easy to tell the various PC's around the house how to access the printer without our needing a Home DNS setup.

Last night we went to Best Buy shopping for a Mifi box that has an x-base-T output. We quickly learned that all the boxes had only Wifi output, no wired port at all. But the guy in the cell phone department suggested we talk to the store's Geek Squad. No joy there as the minimum wage-slave at the Geek Squad desk opined that what I wanted to do couldn't be done, but he suggested we talk to someone in their computer department who is more familiar with the network equipment in stock at Best Buy. So we traipsed over there and finally found someone whose first reaction wasn't "it can't be done". Best Buy has Wifi range extenders from Netgear (model WN2000RPTv2) that not only repeat the Wifi signal but that also bridge the Wifi to a set of 4 100-base-T jacks on the box. So we bought one and an AT&T Mifi box with a 2 year contract, but cancellable within 2 weeks without penalty. So far, so good. The setup of the Netgear box needed me to set a hex password for the _EXT Wifi network that it rebroadcasts. Since no one is going to be using that, I found a web site that can give me random hex digits. I got more than enough hex digits from the site and randomly picked some from the set for my new Wifi's WPA2 password. (My son lives in Silicon Valley, California. I suspect that if he was around he'd have volunteered a 16-sided die to select the needed random hexadecimal digits. There's more than one way to do it...). I pulled the ethernet cable from the cable modem and plugged that cable into a wired port on the Netgear box. Voila! A brdige from Wifi to my home network, wired and wireless both.

So, the main remaining gotcha for me to worry about is that the AT&T Mifi box has an allowance of 5GB/month. We have no idea how many GB/month our home Internet traffic amounts to. So we'll be watching the meter on the Mifi box to see how that goes. A remaining install chore is we want to try to move the home phone lines over to Magic Jack Plus on the home Internet setup. That's the last piece to get the Cablevision cable modem box out of the picture entirely. Then we can see what Cablevision's bill for just television service really looks like and can decide if we want to switch back to satellite TV and read a good book on rainy nights.

We did consider Sprint as an alternative provider of cellular Internet service. They seem to be the one company that has an unlimited cellular data plan available. Alas, Sprint's coverage map shows only 3G service in our area. So, while I was willing to step down to 4G LTE, I wasn't prepared to step as far down as 3G.

A thousand words is worth a picture, and I've got 2 pictures. This first picture sketches out our home Internet setup before today's changes:

Home network yesterday with cable modem

Less than obvious features of the home network: The fireplace wall is thick enough that it attenuated the Wifi signal from the original router in the bedroom to my wife's son's apartment behind that brick wall. A Wifi range extender in the dining room probably would have gotten a strong enough signal to his apartment, but we had an older router on hand, so he ran a cable from the main router to his apartment and set up the older router in the apartment so he has wired and wireless service plentifully available there.

This 2nd picture is just like the first one, except the cable modem is replaced by the Mifi box + the Netgear range extender acting as a bridge between the wired and wireless worlds in the house.

Home network today with Mifi and bridge replacing cable modem

I've already cautioned her son that if and when we go traveling, we'll likely want to take the Mifi box along which will temporarily leave the home network off the Internet. It's a hardknock life. But I think his cell phone can do it's own hotspot trick so he'll get by.

Preliminary findings: With only a fraction of a day of use, we've already burned through a 1/3 of the 5GB allowance. I'm not sure why, but clearly we have to figure that out. Http://pingtest.net had shown pings to Brooklyn taking 14ms with a 2ms jitter on Optimum Online. Through the Mifi arrangement, that same test is now 44ms with a 9ms jitter. Pingtest's site cautions that with that much jitter, we may not be happy with VOIP and Internet game performance. Uh oh.

Any questions? Suggestions? Is your home network "interesting"?

Linus Torvalds on Teaching Children to Program

Linus Torvalds in this less than 3 minute video clip gives a great answer to a question about teaching children how to write computer code. He specifically mentions the Raspberry Pi as having the attractive property of being cheap enough to throw away. I've said before that if you persuade kids to try a computer programming course, some number of them will hate it, and will vow never to wrestle with computer software again. But there should be some who will decide this is fascinating and will pursue it further, perhaps making a career out of it.

http://www.youtube.com/watch?v=2KfJiWR1FPw

My conclusion is that an introductory programming course should therefore be short. I like Udacity CS101. It is nominally only 8 weeks at 5 hours of class time per week. It is self-paced and not on a fixed schedule. You may want to see my blog post: Is the Udacity CS101 Course Watered Down?

There are many possible ways to introduce computer programming. For example, you could pick a commercially important programming language, e.g. C or Java, and organize a course around learning that language. Or you could create/select a student language just for the students to get started with the concepts (Scratch, Logo, Basic, CUPL, ...) and teach that. I think Udacity CS101 chose wisely in picking a subset of Python. Python is a clean, powerful, multi-paradigm programming language that does see some real use commercially. Udacity CS101 doesn't visit all aspects of the language, but it does teach enough of it to give a good start at understanding the construction of computer programs. I believe it is much easier to get started in Python than in C or Java and that Python can carry you a lot further than Scratch, Basic or CUPL.

Another approach to introducing computer programming is to pick projects that are particularly attractive to students. Robots and computer games are two oft-mentioned examples. The parts and tools needed for a Robot-centered course call for a substantial investment ($10-$25 thousand per team is a working estimate I've seen on the web) and also requires comparatively large secure space to store the project, parts and tools. Real-time software that interacts with sensors and motors strikes me as more advanced material then a short introductory course should aim to cover. Games keep the work in the virtual world, so there's less need for parts and a workshop space, but interactive software with graphics is again, in my opinion, more advanced material that a short introductory course should aim to cover. Fair enough to stir into an introductory course a bit of foreshadowing to hint at how the material the course is covering can be extended to work in games or robots.

But I haven't any real experience teaching computer programming to students. I've been trying to launch such a course at the local community center here in the New Cassel section of North Hempstead, NY for well more than a year now, but it hasn't gotten off the ground yet. A shameless plug for yet another of my blog posts: Marketing the Importance of Programming Education. The comment thread on that article is, in my opinion, particularly worth reading.

A reminder: Blog sites such as this one are intended to be 2-way communication, not just reading material. Whether you are a student, teacher, programmer, experienced or inexperienced, you are invited to post comments about this article down below. Suggestions, counter-examples, criticism, pointers to other sites that said it better, and, of course, praise are all welcomed. Anything but spam.

Bicycles for the mind... A Steve Jobs talk from long ago.

1980

In the Introduction talk to Udacity CS101, Professor Evans mentions Steve Jobs having compared computers to "bicycles for the mind".

I think I've now stumbled across the talk where Jobs more or less said that. Run time for the Jobs talk is about 20 minutes. The bicycle reference is around the 6 minute mark in the Jobs video. Evans attributed the quote to circa 1990, but the talk is said to be from 1980, and given Steve's youthful appearance in the video, I believe the 1980 date.

Speaking of small errors, one of the annoying things in Jobs talk is he speaks of meeting with some 4th and 5th graders, but he then calls them 4-5 year-olds. I think 9-11 year-olds would be a lot closer to correct. 20 kids and 6 Apple computers? What a depressing student/machine ratio that would be these days!

Jobs mentions Visicalc in his talk like that is something that everybody in the audience knows of. But here we are some 30+ years later and I'm no longer sure that you all know what Visicalc was. Happily, Wikipedia remembers. Even if you remember Visicalc, I recommend that you visit the Wikipedia page. It has some wonderful interesting links, including one that lets you download a free copy of Visicalc for your x86 Windows PC. That version was written for DOS 1.0 so it only works within the current directory. DOS 1.0 didn't have directories, just disk drives. Most folks back then didn't have disks with any more capacity than a 5.25" floppy disk. In 1980, that would have maybe been 140KB of storage space.

One other link to particularly take note of is the one that asks "What if Visicalc had been patented?". If you haven't been paying attention to the arguments about software patents and why they are not good for the economy, you really should Google up some background reading for yourself, maybe sit through a Richard Stallman talk or 2 about "intellectual property". Be forewarned that Stallman's talk is a 2 hour talk, so take a bathroom break and get yourself a fresh mug of coffee, tea, or whatever before you fire up the Stallman talk.

If I'm going to mention Steve Jobs and Richard Stallman in the same blog post, it is probably appropriate for me to point also you to this short video where Stallman contrasts his own accomplishments vs. those of Jobs and of Bill Gates.

Time marches on, but progress?

Listening to Jobs 1980 predictions for what the heck we'd do with even more computing power, I can't help but be disappointed with how little real progress we've made on that front. The computing power has, of course, materialized as predicted, and I suppose the graphical user interfaces of Windows, MacOS and web browsers is something of a usability improvement compared to DOS 1.0, but I was sending e-mail and posting netnews items aplenty back in 1980 and it isn't like that process is hugely different today. To keep things in perspective, the Macintosh computer was introduced in 1984. Here's an early 1984 video of Steve Jobs giving a timeline leading up to the Macintosh. It's only about 7 minutes long and includes the famous "1984" teaser ad for the Macintosh; an ad still worth watching, in my opinion. Here's a 10 minute video of Steve Jobs actually introducing and demonstrating the Macintosh.

Still, if you have a problem that you want to solve with a computer, are the barriers to solving your problem significantly lower today or about the same despite the powerful GUI computers that are now available today? If there's an existing product that fits your needs ("there's an app for that"), your path is easy, but if you really need custom software, perhaps a custom database, I expect you still have a rough road ahead. "Cobol is to Visicalc as Y is to Z", but what are Y and Z?

Comparing the Python language to the programming languages of 1980 (C, PL/I, Cobol, Fortran) I guess there's some evidence of our having learned to apply plentiful compute power to making the programming job a little easier, but there's still a steep hill to climb to bring computers to bear on your problem, whatever your problem might be. The Internet, the World Wide Web and search engines seems to be the most evident signs of progress in the computing world since 1980. I do wish the world had more progress to show on reducing the barriers to applying computers to solve problems given the passage of 30+ years since that Jobs talk. Are there specific improvements in the computing world that I'm overlooking here and not giving proper credit to? Should smartphones get mention or are they just scaled down screens with battery powered small computers.

If I was better at HTML, maybe I could rig this article to provide background music as you read the previous paragraph. Or am I being too sentimental about lack of technological progress?

If you are completely unfamiliar with Stallman's contributions to the notions of "free software", you might give a quick read of a past blog post of my own as a way to get started at understanding software licensing and Stallman's GPL in particular: See "Copied Code or Unfortunate Coincidence".

06/11/2014 - Updated: The Steve Jobs talk link went bad! Why didn't anyone tell me with a comment so I'd know? Anyhow, I found a link that works (today).

Control Engineering?

My Master's degree

My MSE is from U. of Michigan, Ann Arbor. As I previously explained in a STEM post, I was there in a program sponsored by Bell Labs called "One Year On Campus". Within a maximum of 12 months, it was a requirement for my continued employment to complete a Master's of Science, Engineering degree. The Labs imposed a few additional requirements on the courses I was to take. I was to take an information theory and communications course (modulation techniques, etc., etc.), a digital logic course, and I'm not sure what all else. My main interest was in studying computer science, but the University had a requirement that X% of your courses had to be from within the department of your major. For broad studies of computing, that was a problem as the computing courses were spread throughout the University. The digital logic, machine architecture and assembly language courses were over in the Electrical Engineering department. The computer graphics courses were in the Industrial Engineering department. Operating systems, higher level languages and compilers were in the Computer Science department. Database courses were way over in the business school. So, the Engineering school created the "CICE - Computer, Information and Control Engineering" department to cross list all of the above courses. By majoring in CICE, I was able to take a broad variety of computing courses and still meet that X% within my major department requirement.

So much to do and only a year to do it. So, I admit that the edge of the CICE curriculum where I did not fit in many courses was control engineering. I had some exposure to it, but just enough to hum along if someone decided to sing about the subject. I couldn't even confidently promise to you a competent explanation of the topic if you asked me about it.

TED talk/demo of control engineering

So, I was excited today to find a most excellent TED talk demonstrating control engineering with a set of "Quad copters". The talk has some very impressive demonstrations of software control of the copters. I could wish for a more technical explanation then they offered. I'm not at all sure how many processors of what kind they used to track and control the copters. I'm pretty sure there's more real-time computation going on there then would comfortably fit into one processor, but that's just my gut feeling and not based on any real experience.

And so, for your entertainment and to convey to you what the heck "control engineering" is about, I share with you Raffaello D'Andrea: The astounding athletic power of quadcopters from June 2013. Run time of the video is about 16 minutes.

Want to know more?

I did some mild Google searching to try to find the source code for the control programs, which I assume are likely to be "open source". I didn't find exactly what I was looking for. But I did find some useful info. There's a Wikipedia article about Quadcopters and from there, there are plenty of links to additional information. I found this article about the lab where they test their stuff to be interesting. I was heartened to learn that they do have a safety net to catch the falling copters when the software is still under development. The article does give me the distinct impression that they've developed custom hardware to do the control algorithms fast enough. That is a potential major obstacle for a casual hobbyist who wants to play. If the Wikipedia article doesn't give you enough leads to follow there's an existing Pearltree specifically about quadcopters. I did find some open source (Arduino controller) quadcopter projects. e.g. this one and another one.

If you try your own Google searches, be careful about people in other fields of research with names similar to Raffaello D'Andrea. e.g. I found a biology PhD candidate at U. of Michigan named Rafael D'Andrea - Not the same guy. Oh, and I did find some Cornell U. work in the field of quadcopters too: Autonomous Quadcopter Docking System. Oh my, on page 11 of that report, the guy strapped his Android Smartphone to the quadcopter to add a camera to the configuration. That must have taken guts! (I wonder if he has the "Send me to Heaven" game on his Android phone? Not me!)

If you want to get into the math of control of a quadcopter, this looks like a reasonable place to start reading: Estimation and Control for an Open-Source Quadcopter. Or just sit back and enjoy the demo video that I pointed to in the previous section. Not everyone has to be a DIY engineer with amazing toys.

SOLID software design...

My hopeless backlog

One of the bad habits I have is accumulating lists of things to read. Google Reader used to be a handy place to categorize and keep my "subscriptions" to blogs and so forth to read. Unfortunately, Google pulled the plug on that service in July. Fortunately, another web service, theoldreader.com provided a very similar free service. In fact, their service was designed to look like an earlier version of Google Reader. Some time ago, Google removed some "social" aspects of Google Reader and the change irked some of their users. theoldreader.com sprung up to undo the perceived damage of Google's changes. When Google announced the planned demise of the Google Reader service, Google at least was kind enough to provide a mechanism for retrieving my list of subscriptions, so I opened a free account with theoldreader.com and submitted my subscription list. But so did a zillion other people, so it took literally weeks for the site to get around to processing my subscription list. In the fullness of time, they did get the subscriptions into their system and it seemed usable enough, but then their servers crumbled under the newly stepped up load. (Well, I think that the story is more like they made changes to beef up their servers and in making the changes someone tripped over a power cord or something). More days and days of noticeable downtime before things got back on the air and seemingly stable again.

My point in mentioning Blog subscriptions is that the universe conspires to generate "interesting" blog articles faster than I manage to read them. "Another day older and deeper in debt...". My backlog of unread blog articles is quite hopeless, but whenever I have nothing much to do, instead of turning on the boob-tube in the living room, I fire up theoldreader.com in my browser and try to read up on what I've been missing.

If you've got your own solution to tracking new blog articles, I hope my blog here is on your subscription list. If not, please take a moment to sign-up my blog onto your list. Go ahead and do it now. I'll wait for you to get back. (Full disclosure: No one has ever told me of positive or negative experiences from subscribing to my blog with their favorite RSS tool. I'm assuming that blogspot.com does the right thing, but if you run into a snag, I'd sure like to hear about it).

Emily's "Coding is Like Cooking" blog

One of the blogs that I do try to keep up with is from an expert on test-driven-development (TDD) named Emily Bache, an Englishwoman who now lives and works in Sweden. Her blog is called "Coding is Like Cooking". I like it because it tends to be quite well written and covers relatively recent software development topics that I might otherwise miss out on. i.e. Stuff that I didn't learn in school back in the days when Structured Programming was still somewhat controversial, and that I didn't pick up by osmosis in the later years of my employment at Bell Labs. I freely confess that Test-Driven-Development wasn't part of the quite informal methodology that "we" in Math Research were following. The mathematicians tended to find the underlying math of the problems far more interesting then the structure of the code. I also found myself unexposed to a great mentor for Object-Oriented-Programming. Java got some use in our projects, but I knew enough to recognize bad use of the language when I saw it. So, now I'm retired and still have much to learn. The web has no shortage of material for me to learn from and by reading Emily's articles and saying "Huh?" when something comes up that isn't at all familiar to me, I find lots of great stuff to learn.

One of my "Huh?" moments came from her mention of the "London School". I followed her link and picked up a book for my Amazon book Wish list: Growing Object-Oriented Software, Guided by Tests

SOLID Principles and TDD

So today I was reading an article of her's from September, 2012, SOLID principles and TDD. I didn't get very far into it when my brain complained "Huh? What does she mean by SOLID?". So I opened up another window thanks to a link she provided and read the Wikipedia article on SOLID. It isn't a particularly excellent Wikipedia article. It is dense with off-putting terminology - might be the fault of the SOLID acronym and not really the fault of the article - I've got to forgive the Wikipedia article because it has some excellent links to reference material.

Uncle Bob's principles of Object Oriented Design

One of the links from Wikipedia that I followed was http://butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod. Still more links to clarify the mysterious-to-me parts of that SOLID acronym. This summary article looks especially good: http://www.objectmentor.com/resources/articles/Principles_and_Patterns.pdf.

And just to make sure I don't run out of things to read, there's a book mentioned and even recommended by another reader - Agile Software Development, Principles, Patterns, and Practices that I've added to my Amazon "Agile" book wish list to remind me I really need to take a look at it.

In closing...

So, my situation is quite hopeless if the goal is to finish reading the stuff on my list. If I'm reading anything interesting, it tends to add more things to my list. And that doesn't even count the time to actually try the tools and techniques that I'm reading about. I hope you found some of this material interesting enough to add to your own read-and-try list. I guess I have a bit of a sadistic streak to want to inflict my backlog on other folks.

Learned anything interesting lately?

Learn How to Program Computers!

Say What?

News photo of an experimental self-driving Volvo from Engadget report.

Computer procesors show up almost everywhere these days. Desktops, laptops, cell phones, processors embedded in cars, processors embedded in printers, embedded in cameras, embedded in dish-washers.

One thing that they all have in common is that someone (or some team of folks) had to develop a set of instructions to guide the computer to do whatever it is that it does. Those instructions are called programs, software, and the stuff that goes into a program is called "code", not to be confused with "secret codes", though there is a connection if cryptography is what interests you.

So, no matter what, you are pretty much fated to be a user of computer programs, but with some effort on your part, you can learn to write your own computer programs too. Creating a computer program is called "software development". You can learn to do software development on your own. I'll caution up front that seriously big projects generally are tackled by teams, not individuals working solo. But the longest journey starts with but a single step.

My intent here is to convince you that you should embark on the long journey of learning to program computers, to do software development.

Motive

There are plenty of reasons why you should learn how to program computers. Before you begin on that path, you might want to think about what your motive is. Are you hoping to write your own computer games? Want to understand Cyberwarfare before you are noted as a threat by Skynet? Interested in autonomous robots? Self-driving cars? Want to develop a fancy web site of your own? Thinking it might be a useful skill when seeking a serious job? Want to understand how the NSA accidentally intercepted calls from Washington, DC, when they meant to intercept calls from Egypt?

I can't tell you what motivates you. I will caution that this is no short trip, so you should probably be sure you are well motivated before you dive in.

I'll also mention up front that the early days of getting started with developing your own software can be frustrating. As you master the basics, a self-driving car may seem awfully far away. Part of my hope here is that I can convince you that if you keep your motive in mind, you can work through the steep initial learning curve.

Age restrictions?

In my opinion, there's no upper bound on the age when you can learn to program computers. If you are past retirement age, that might alter your own list of motives for learning, but it is no reason to refuse to give it a try.

Can you be too young to learn to program? Well, programming does generally involve reading and writing, so if you haven't gotten proficient at those skills yet, you may find it hard to get into software development. But then, how is it that you are reading this article? The US apparently has regulations that strongly discourage web sites from registering information for children under age 13, so if you are under age 13, it is important that you discuss your plans with your parent or guardian and have permission from them to get involved in online courses.

Cost?

If you have access to a computer with a good Internet connection, you probably have all that you need to get started. If you don't, then how is it that you are reading this article?

Of course, if you have money to invest in this project of yours, there are things you might want to look into. For instance, books. You can get plenty of materials for free here on the Internet, but sometimes it can be useful to have a paper document that you can bookmark, dog-ear, highlight and annotate. Don't feel you have to invest in books up front, but if you can find a good local book store, you may find that there are useful things to be found by browsing. Your local library may also be useful, though in my experience, the local library tends to be woefully short of current technical books. The good news is that if you can find titles worth looking at, perhaps from web searches of places like amazon.com, then most likely your local library can arrange an inter-library loan so you can examine the book without having to buy it first.

Of course, library books, including books borrowed on inter-library loans, need to be treated politely, not dog-eared, high-lighted and given marginal annotations. And they do have to be returned after a relatively short time. If you find a title that looks really well matched to your needs, that's where you just might blow your allowance on an order from an online book-seller, so you'll have a copy of it for your own. Amazon.com does have provisions for wish lists, sort of like bridal registries, so as you publically grow your list of titles you hunger for, you'll at least make it easy for folks thinking about getting you a birthday present or Christmas present.

Libraries can also be a great place for getting free public access to Internet-connected computers. You might find that there are administrative obstacles to your installing software development tools on the library's PC's, or even filters to protect you from the educational materials. Don't let those barriers stop you. Talk to the librarian to find out who is in charge of those kinds of filters. Most likely, arrangements can be made for good reasons like you have.

Courses?

There are many computer programming courses available on the Internet for free. "Massive Open Online Courses", MOOC's, featuring different programming languages and different levels of material. Some aim to serve particularly younger students. You might look, for example, for courses that introduce the "Scratch" programming language.

I haven't taken a "Scratch" course myself, so I'm not going to single out a specific suggestion here. Just try a simple Google search for:

    scratch programming course

and let us know in a comment which course you picked and why, and how that went for you.

But if you feel you are ready to learn a somewhat more conventional programming language, one that will take you further than I believe Scratch will, my suggestion is CS101 from Udacity.com, where you will learn to program using the Python 2 programming language.

The Python programming language continues to evolve. There are Python 3 versions available today. The world is still catching up to that. You'll be fine starting with Python 2, and learning the differences later on to get over to the newer versions. It is important that you know that there are multiple versions and that when you are shopping for books or tools that you get a version that matches what the course is expecting you to have.

There are other courses available, though I haven't tried the others myself. Certainly there are courses that teach Python specifically for game development. And there are plenty of courses that teach other languages, Java and C, for example. But in my opinion, CS101 from Udacity.com is a good place to start. It is free, self-paced, you work on it on your own schedule. Nominally, it is an 8-week course. It doesn't have pre-requisite other courses. I believe it is an excellent place to get started with MOOC's. There's a final exam at the end and when you pass it, they will e-mail to you a certificate to commemorate your accomplishment. There are reports on the web of real colleges that even give credits if you are a registered student and pass the Udacity.com CS101 course, but being a registered student at a physical college is outside the realm of stuff you can try for no charge.

If nothing else, trying a MOOC to get started will show you if this is a field that holds your interest. I know software development has been a long standing interest of my own, but I also know that some fraction of the students who try it find that they absolutely hate programming. If you find that's the case for you, my advice is that you tough it out to completion of the introductory course and then look for other fields that do hold your interest. It's only a couple of months to work through Udacity CS101, and it isn't anything like a full-time course load while you are working through just the introductory course. Getting the certificate isn't good motive to start the course, but perhaps it is a good motive to stick it out to the end.

Where to find more?

code.org is a web site that advocates that everyone should learn how to code. They offer 3 editions of a promotional video to promote interest in the field. One is a 1-minute teaser. Another is a 5-minute edition featured on their web site's front page. And if you have 10-minutes to spare, there is a full edition available.

There are links on the code.org site to various local places to learn to program. For example, there's a brief plug there for the "Yes We Can Community Center" here in Westbury, NY.

Details of the schedule are not yet nailed down for Fall 2013, but if you are local to here, one way to take on CS101 is to sign up with the Community Center. The Center has the computers and Internet access, and it will have other students so you won't feel too much that you are on-your-own. And, for what it worth, I'll be available to answer questions and help keep you motivated while you are working through the course online.

Not quite free, as there is a membership fee to sign up with the Community Center. But use of the basketball courts, game room and locker room and access to quiet study space for your homework time all come with that membership, so it's probably worth joining if this is your community. (Use of the fitness center is not included in basic membership. Sorry).

The schedule I've proposed is that Monday evenings we'd meet as a class to share discussion of progress and problems. Other school nights I'd be available to answer questions 7-9PM or by appointment.

In any case, you can try udacity.com CS101 on your own before we even get started and then continue at the Community center once we get our act together there. Please, do let them know at the front desk that you're interested in taking CS101 as seating is limited.

Free for Senior Citizens

If you are a resident of North Hempstead and are age 60 or more, you are eligible for free membership in Project Independence and get a free community center membership too when you join Project Independence. Such a deal!

Further reading

Benefits of Teaching Kids To Code That No One Is Talking About - This blog post by an online acquaintance of mine has an example of a Scratch program, and a link to a video of a talk by the creator of Scratch.

Is Udacity CS101 Watered Down - This is a blog post from me in December 2012, describing what you should expect to get out of the online Udacity CS101 course.

Where to Get Python - This is another blog post from me. This one describes how you can install Python on your own PC. Note that back when I wrote that, Udacity was still using Python 2.6, but the course has since updated it's software to Python 2.7. From an end-user point of view that's an almost imperceptible change.

There are numerous Youtube videos available about learning to program games. Here is Episode 1 of a series that is dozens of videos long. Part 1 shows off a couple of games the guy has written in Python and describes what prerequisite knowledge he expects you to have to get started with his tutorials.

This isn't the first time that I've written about plans for CS101 at the Community Center. For more details of my intended format for the weekly meetings, see my blog article: Marketing the Importance of Programming Education