| g1 | g2 | g3 | g4 |
| (1,2,x,4) | (1,2,x,4) | (1,2,x,4) | (1,2,x,4) |
| (1,2,y,4) | (1,2,y,4) | (1,2,y,4) | (1,2,y,4) |
| (a,b,c,d) | (e,f,g,h) | (1,2,3,4) | (i,j,k,l) |
| (1,2,z,4) | (1,2,z,4) | (1,2,z,4) | (1,2,z,4) |
Oct 23, 2015
Задача византийских генералов
Википедия: Задача византийских генералов
Sep 4, 2015
Aug 19, 2015
“Маркетолог спрашивает программиста: в чём сложность поддержки большого проекта?
Программист: ну представь, что ты писатель и поддерживаешь проект “Война и мир”. У тебя ТЗ — написать главу как Наташа Ростова гуляла под дождём по парку. Ты пишешь “шёл дождь”, сохраняешь, вылетает сообщение об ошибке “Наташа Ростова умерла, продолжение невозможно”. Почему умерла? Начинаешь разбираться. Выясняется, что у Пьера Безухова скользкие туфли, он упал, его пистолет ударился о землю и выстрелил в столб, а пуля от столба срикошетила в Наташу. Что делать? Зарядить пистолет холостыми? Поменять туфли? Решили убрать столб. Получаем сообщение “Поручик Ржевский умер.” Выясняется, что он в следующей главе облокачивается о столб, которого уже нет..”
Программист: ну представь, что ты писатель и поддерживаешь проект “Война и мир”. У тебя ТЗ — написать главу как Наташа Ростова гуляла под дождём по парку. Ты пишешь “шёл дождь”, сохраняешь, вылетает сообщение об ошибке “Наташа Ростова умерла, продолжение невозможно”. Почему умерла? Начинаешь разбираться. Выясняется, что у Пьера Безухова скользкие туфли, он упал, его пистолет ударился о землю и выстрелил в столб, а пуля от столба срикошетила в Наташу. Что делать? Зарядить пистолет холостыми? Поменять туфли? Решили убрать столб. Получаем сообщение “Поручик Ржевский умер.” Выясняется, что он в следующей главе облокачивается о столб, которого уже нет..”
Jun 22, 2015
Jun 8, 2015
Parallel Programming
Amdahl's law
The speedup of a program using multiple processors in parallel computing is limited by the time needed for the sequential fraction of the program. For example, if a program needs 20 hours using a single processor core, and a particular portion of the program which takes one hour to execute cannot be parallelized, while the remaining 19 hours (95%) of execution time can be parallelized, then regardless of how many processors are devoted to a parallelized execution of this program, the minimum execution time cannot be less than that critical one hour. Hence the speedup is limited to at most 20×.
Gustafson–Barsis' law
Says that computations involving arbitrarily large data sets can be efficiently parallelized.
The speedup of a program using multiple processors in parallel computing is limited by the time needed for the sequential fraction of the program. For example, if a program needs 20 hours using a single processor core, and a particular portion of the program which takes one hour to execute cannot be parallelized, while the remaining 19 hours (95%) of execution time can be parallelized, then regardless of how many processors are devoted to a parallelized execution of this program, the minimum execution time cannot be less than that critical one hour. Hence the speedup is limited to at most 20×.
Gustafson–Barsis' law
Says that computations involving arbitrarily large data sets can be efficiently parallelized.
May 21, 2015
May 13, 2015
May 5, 2015
У скольких целых чисел, лежащих в диапазоне от 1 до 1000, есть цифра 3?
Сначала узнаем, сколько чисел не имеют 3 в своей записи. Для этого на каждое место ставим 9 цифр, не включающие 3 т.е. 9 * 9 * 9 = 729. Если всего чисел 1000, то ответ 1000 – 729 = 271.
http://tproger.ru/problems/count-digit-3-in-numbers-from-1-to-1000/Apr 29, 2015
JIT
JIT in Python via LLVM
http://eli.thegreenplace.net/2015/building-and-using-llvmlite-a-basic-example/
http://eli.thegreenplace.net/2012/08/10/building-and-using-llvmpy-a-basic-example
http://nullprogram.com/blog/2015/03/19/ A Basic Just-In-Time Compiler
http://www.tedunangst.com/flak/post/now-or-never-exec how to add PROT_EXEC on mmap
http://eli.thegreenplace.net/2015/building-and-using-llvmlite-a-basic-example/
http://eli.thegreenplace.net/2012/08/10/building-and-using-llvmpy-a-basic-example
http://nullprogram.com/blog/2015/03/19/ A Basic Just-In-Time Compiler
http://www.tedunangst.com/flak/post/now-or-never-exec how to add PROT_EXEC on mmap
Apr 28, 2015
Apr 16, 2015
Mar 25, 2015
Mar 17, 2015
Mar 5, 2015
Feb 24, 2015
Feb 11, 2015
Feb 10, 2015
Feb 9, 2015
If Carpenters Were Hired Like Programmers
Interviewer: So, you're a carpenter, are you?Carpenter: That's right, that's what I do.
Interviewer: How long have you been doing it?
Carpenter: Ten years.
Interviewer: Great, that's good. Now, I have a few technical questions to ask you to see if you're a fit for our team. OK?
Carpenter: Sure, that'd be fine.
Interviewer: First of all, we're working in a subdivision building a lot of brown houses. Have you built a lot of brown houses before?
Carpenter: Well, I'm a carpenter, so I build houses, and people pretty much paint them the way they want.
Interviewer: Yes, I understand that, but can you give me an idea of how much experience you have with brown? Roughly.
Carpenter: Gosh, I really don't know. Once they're built I don't care what color they get painted. Maybe six months?
Interviewer: Six months? Well, we were looking for someone with a lot more brown experience, but let me ask you some more questions.
Carpenter: Well, OK, but paint is paint, you know.
Interviewer: Yes, well. What about walnut?
Carpenter: What about it?
Interviewer: Have you worked much with walnut?
Carpenter: Sure, walnut, pine, oak, mahogony -- you name it.
Interviewer: But how many years of walnut do you have?
Carpenter: Gosh, I really don't know -- was I supposed to be counting the walnut?
Interviewer: Well, estimate for me.
Carpenter: OK, I'd say I have a year and a half of walnut.
Interviewer: Would you say you're an entry level walnut guy or a walnut guru?
Carpenter: A walnut guru? What's a walnut guru? Sure, I've used walnut.
Interviewer: But you're not a walnut guru?
Carpenter: Well, I'm a carpenter, so I've worked with all kinds of wood, you know, and there are some differences, but I think if you're a good carpenter ...
Interviewer: Yes, yes, but we're using Walnut, is that OK?
Carpenter: Walnut is fine! Whatever you want. I'm a carpenter.
Interviewer: What about black walnut?
Carpenter: What about it?
Interviewer: Well we've had some walnut carpenters in here, but come to find out they weren't black walnut carpenters. Do you have black walnut experience?
Carpenter: Sure, a little. It'd be good to have more for my resume, I suppose.
Interviewer: OK. Hang on let me check off the box...
Carpenter: Go right ahead.
Interviewer: OK, one more thing for today. We're using Rock 5.1 to bang nails with. Have you used Rock 5.1?
Carpenter: [Turning white...] Well, I know a lot of carpenters are starting to use rocks to bang nails with since Craftsman bought a quarry, but you know, to be honest I've had more luck with my nailgun. Or a hammer, for that matter. I find I hit my fingers too much with the rock, and my other hand hurts because the rock is so big.
Interviewer: But other companies are using rocks. Are you saying rocks don't work?
Carpenter: No, I'm not saying rocks don't work, exactly, it's just that I think nail guns work better.
Interviewer: Well, our architects have all started using rocks, and they like it.
Carpenter: Well, sure they do, but I bang nails all day, and -- well, look, I need the work, so I'm definitely willing to use rocks if you want. I try to keep an open mind.
Interviewer: OK, well we have a few other candidates we're looking at, so we'll let you know.
Carpenter: Well, thanks for your time. I enjoyed meeting you.
NEXT DAY:
Ring...
Interviewer: Hello?
Carpenter: Hello. Remember me, I'm the carpenter you interviewed for the black walnut job. Just wanted to touch base to see if you've made a decision.
Interviewer: Actually, we have. We liked your experience overall, but we decided to go with someone who has done a lot of work with brown.
Carpenter: Really, is that it? So I lost the job because I didn't have enough brown?
Interviewer: Well, it was partly that, but partly we got the other fellow a lot cheaper.
Carpenter: Really -- how much experience does he have?
Interviewer: Well, he's not really a carpenter, he's a car salesman -- but he's sold a lot of brown cars and he's worked with walnut interiors.
Carpenter: [click]
http://www.jasonbock.net/jb/News/Item/7c334037d1a9437d9fa6506e2f35eaac
Interviewer: How long have you been doing it?
Carpenter: Ten years.
Interviewer: Great, that's good. Now, I have a few technical questions to ask you to see if you're a fit for our team. OK?
Carpenter: Sure, that'd be fine.
Interviewer: First of all, we're working in a subdivision building a lot of brown houses. Have you built a lot of brown houses before?
Carpenter: Well, I'm a carpenter, so I build houses, and people pretty much paint them the way they want.
Interviewer: Yes, I understand that, but can you give me an idea of how much experience you have with brown? Roughly.
Carpenter: Gosh, I really don't know. Once they're built I don't care what color they get painted. Maybe six months?
Interviewer: Six months? Well, we were looking for someone with a lot more brown experience, but let me ask you some more questions.
Carpenter: Well, OK, but paint is paint, you know.
Interviewer: Yes, well. What about walnut?
Carpenter: What about it?
Interviewer: Have you worked much with walnut?
Carpenter: Sure, walnut, pine, oak, mahogony -- you name it.
Interviewer: But how many years of walnut do you have?
Carpenter: Gosh, I really don't know -- was I supposed to be counting the walnut?
Interviewer: Well, estimate for me.
Carpenter: OK, I'd say I have a year and a half of walnut.
Interviewer: Would you say you're an entry level walnut guy or a walnut guru?
Carpenter: A walnut guru? What's a walnut guru? Sure, I've used walnut.
Interviewer: But you're not a walnut guru?
Carpenter: Well, I'm a carpenter, so I've worked with all kinds of wood, you know, and there are some differences, but I think if you're a good carpenter ...
Interviewer: Yes, yes, but we're using Walnut, is that OK?
Carpenter: Walnut is fine! Whatever you want. I'm a carpenter.
Interviewer: What about black walnut?
Carpenter: What about it?
Interviewer: Well we've had some walnut carpenters in here, but come to find out they weren't black walnut carpenters. Do you have black walnut experience?
Carpenter: Sure, a little. It'd be good to have more for my resume, I suppose.
Interviewer: OK. Hang on let me check off the box...
Carpenter: Go right ahead.
Interviewer: OK, one more thing for today. We're using Rock 5.1 to bang nails with. Have you used Rock 5.1?
Carpenter: [Turning white...] Well, I know a lot of carpenters are starting to use rocks to bang nails with since Craftsman bought a quarry, but you know, to be honest I've had more luck with my nailgun. Or a hammer, for that matter. I find I hit my fingers too much with the rock, and my other hand hurts because the rock is so big.
Interviewer: But other companies are using rocks. Are you saying rocks don't work?
Carpenter: No, I'm not saying rocks don't work, exactly, it's just that I think nail guns work better.
Interviewer: Well, our architects have all started using rocks, and they like it.
Carpenter: Well, sure they do, but I bang nails all day, and -- well, look, I need the work, so I'm definitely willing to use rocks if you want. I try to keep an open mind.
Interviewer: OK, well we have a few other candidates we're looking at, so we'll let you know.
Carpenter: Well, thanks for your time. I enjoyed meeting you.
NEXT DAY:
Ring...
Interviewer: Hello?
Carpenter: Hello. Remember me, I'm the carpenter you interviewed for the black walnut job. Just wanted to touch base to see if you've made a decision.
Interviewer: Actually, we have. We liked your experience overall, but we decided to go with someone who has done a lot of work with brown.
Carpenter: Really, is that it? So I lost the job because I didn't have enough brown?
Interviewer: Well, it was partly that, but partly we got the other fellow a lot cheaper.
Carpenter: Really -- how much experience does he have?
Interviewer: Well, he's not really a carpenter, he's a car salesman -- but he's sold a lot of brown cars and he's worked with walnut interiors.
Carpenter: [click]
http://www.jasonbock.net/jb/News/Item/7c334037d1a9437d9fa6506e2f35eaac
Feb 5, 2015
Jan 21, 2015
Jan 9, 2015
Software Design Patterns
http://en.wikipedia.org/wiki/Software_design_pattern
http://sourcemaking.com/design_patterns
http://martinfowler.com/eaaCatalog/
http://design-pattern.ru/patterns (ru)
Python Implementations
https://github.com/faif/python-patterns
https://github.com/gennad/Design-Patterns-in-Python
http://python-3-patterns-idioms-test.readthedocs.org/en/latest/Part3.html
Articles
http://habrahabr.ru/post/184156/
http://sourcemaking.com/design_patterns
http://martinfowler.com/eaaCatalog/
http://design-pattern.ru/patterns (ru)
Python Implementations
https://github.com/faif/python-patterns
https://github.com/gennad/Design-Patterns-in-Python
http://python-3-patterns-idioms-test.readthedocs.org/en/latest/Part3.html
Articles
http://habrahabr.ru/post/184156/
Jan 6, 2015
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