8 ms·

I had been harboring some suspicions that our big codebases might benefit from the application of some more of the various “modern” C++ design patterns, despite

by pkaler 16y ago

I had been harboring some suspicions that our big codebases might benefit from the application of some more of the various “modern” C++ design patterns, despite seeing other large game codebases suffer under them. I have since recanted that suspicion. Quoted for truth. I learned C++ during the Meyers/Sutter era. Then Andrei Alexandrescu came along and I had Boost libraries sprinkled all over my code. My beard is growing grey and these days my C++ looks more and more like straight up C.

colkassad 16y ago
I found this part of his article to be interesting. I'm working through a CS degree and learning C++ for the first time after cutting my teeth on Python and C#. What exactly does he mean by "(restrained) C++"? He mentions a contract studio using the STL and boost. We are using the STL in our data structures class...does John Carmack eschew the STL and roll his own data structures?
- cosbynator 16y ago
  In his own words: http://twitter.com/#!/ID_AA_Carmack/status/21119808432 http://twitter.com/#!/ID_AA_Carmack/status/21119808432 I consider myself a decent programmer but I have more trouble reading template heavy C++ than I do haskell code. To me, restrained C++ means keeping the unreadable bits outside the code base and isolated in their own library, like Boost :)
  - dhess 16y ago
    One problem with C++ templates is that they're infectious. You're right that the Boost source code is quite unreadable compared to vanilla C++, but even using Boost types and algorithms in your own code often makes it impenetrable, too.
  - InclinedPlane 16y ago
    Template meta programming is very neat stuff, but the problem is that it's basically another language that lives on top of your language. Except that it's not a full-fledged language so it lacks all of the features that keep other programming languages manageable. It's like assembly code, except instead of just twiddling some bits in registers and RAM you're working with a far more complicated entity (an entire program), making the problem that much worse.
- dgant 16y ago
  C++ lends itself to a large variety of different programming styles and paradigms. C++ also lends itself to premature baldness, by developers ripping their hair out trying to make systems developed in different styles interact with each other. A popular thought is that any given team or company should pick a particular subset of those styles -- and perhaps a subset of C++'s features -- and use them to the exclusion of others.
- pkaler 16y ago
  Kids these days with their allocations and virtual memory. shakes fist You don't need std::vector if you don't need dynamic memory allocations. Game programming and systems programming is a whole lot different than web or desktop development. For games, you create a memory budget up front. You decide how much memory sound, textures, models, AI will consume up front and then statically allocate that memory up front. http://gamesfromwithin.com/start-pre-allocating-and-stop-worrying http://gamesfromwithin.com/start-pre-allocating-and-stop-wor... You can statically allocate at the start of a game, level, and frame. From the original article: OpenAL appears to have a limit of 1024 sound buffers, which we bumped into. We could dynamically create and destroy the static buffer mappings without too much trouble, but that is a reasonable number for us to stay under. It also sounds like Carmack is loading an entire level as a memory mapped file and then doing reads into specific indexes within the file. Take a look at the source code that id has open sourced. That's the best way to get a feel how this style of development works. I believe RtCW is their last release. ftp://ftp.idsoftware.com/idstuff/source/ http://github.com/monoid/rtcw-rebirth http://github.com/monoid/rtcw-rebirth
  - colkassad 16y ago
    Actually, I'm 38...bit of a late starter :) Thanks for the reply and link. Modeling and simulation is my area of interest (I work in civil and environmental engineering), so it will be interesting to see what patterns will work best.
- edderly 16y ago
  Google gives a good take on restrained C++: http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml http://google-styleguide.googlecode.com/svn/trunk/cppguide.x...
  - colkassad 16y ago
    Nice, I read this a long time ago before learning C++. It's interesting (and reassuring) that some of the stuff we are learning is considered bad practice by Google.
tzs 16y ago
My C++ also tends to be simple. I also have never had a need for any formal "design patterns", as every time I've encountered a problem for which it turns out there is named pattern in the books, a few moments thought about the problem has always led me to discover the solution myself. Now, it could be that this means I'm some kind of programming genius. I wish that were true, but alas I think it is not so much a reflection of how good I am, but rather how mediocre many programmers are today.
- aaronblohowiak 16y ago
  "Design Patterns" exists to give a common vocabulary to the things we do with code and discuss the proper application of the techniques.
np3000 16y ago
Some more Carmack tweets on C++ IMO, good C++ code is better than good C code, but bad C++ can be much, much worse than bad C code. 10:17 AM Oct 6th I wish C++ had a "functional" qualifier to enforce no global references or side effects. 11:16 PM Sep 21st Reading More Effective C++. I have grown to appreciate at least some uses of most C++ features, but I still don't buy in on exceptions. 10:26 PM Aug 13th
- dhess 16y ago
  I'm no C++ fan (anymore), either, but I don't understand Carmack's taking exception with exceptions. If the alternative is guarding every function call with an if statement to check for error codes, I'll take exceptions almost every time. (Many game programmers I know think that checking for errors is usually bad game programming style, period, but I'm assuming Carmack isn't one of those people.) Exceptions do have possibly deleterious effects on performance, but then, you can just be judicious about where you use them. Exceptions are at least appropriate for catastrophic failures like, "Oops, the game just crashed," or, "Your network connection died." Thinking about manually unwinding out of a game-over failure like that makes me grimace. Sigh, game programmers. :)
  - pkaler 16y ago
    Throwing an exception is a misnomer. An exception doesn't necessarily mean that an error happened. It means, "please unwind the call stack". Unwinding the call stack in a game is a no-no. Games, especially the simulation, must be deterministic. An exception would most likely destroy determinism. The simulation/AI is a big, hairy, ugly set of if/else and switch statements anyway. Adding extra error checking is not an extra burden. The visualization sends asynchronous commands from the CPU to the GPU. The error condition won't be known right away. Querying the GPU will cause a flush of your command stream and ruin performance. Dynamic memory allocation is reduced to a minimum during a frame so you don't get out of memory errors. Strings are allocated in a pool. Network sockets, file handles, and other performance intensive resources are not created mid-frame. Exceptions are not a win for games. It is usually best to run the entire frame and then check for errors all at once at the end.
dhess 16y ago
I'm on the same arc (especially the template Kool-Aid phase), except perhaps further along: now I forgo C++ entirely and write plain C because it's so much easier to wrap from higher-level languages. I do miss smart pointers, but on the other hand, dealing with malloc and friends keeps me honest about what really needs to be written in C.
- acqq 16y ago
  For the high performance stuff I write my kind of restrained C++: never STL in the interfaces of the "modules," use STL algorithms (they are good) but otherwise manage memory in custom ways (which is easier by not using STL containers!). But I had to solve one interesting problem using some recursive definitions and code, and discovered that once I "freed" the code from classes (made them C functions) I was able to express it properly -- just having them as members prevented me to see that the solution is much more obvious when you actually use plain pointers and don't think about the same "object" even during the life of the function. Add to that in the member "this" can't be null. When you need real expressiveness, C can't be beaten. C++ syntactic sugar helps sometimes, but limiting to it is... limiting!
sandGorgon 16y ago
Do you use STL then ? Because, that was pretty much the only reason I started using C++. Or do you write your own containers

by pkaler 16y ago

colkassad 16y ago

I found this part of his article to be interesting. I'm working through a CS degree and learning C++ for the first time after cutting my teeth on Python and C#. What exactly does he mean by "(restrained) C++"? He mentions a contract studio using the STL and boost. We are using the STL in our data structures class...does John Carmack eschew the STL and roll his own data structures?

cosbynator 16y ago
In his own words: http://twitter.com/#!/ID_AA_Carmack/status/21119808432 http://twitter.com/#!/ID_AA_Carmack/status/21119808432 I consider myself a decent programmer but I have more trouble reading template heavy C++ than I do haskell code. To me, restrained C++ means keeping the unreadable bits outside the code base and isolated in their own library, like Boost :)
- dhess 16y ago
  One problem with C++ templates is that they're infectious. You're right that the Boost source code is quite unreadable compared to vanilla C++, but even using Boost types and algorithms in your own code often makes it impenetrable, too.
- InclinedPlane 16y ago
  Template meta programming is very neat stuff, but the problem is that it's basically another language that lives on top of your language. Except that it's not a full-fledged language so it lacks all of the features that keep other programming languages manageable. It's like assembly code, except instead of just twiddling some bits in registers and RAM you're working with a far more complicated entity (an entire program), making the problem that much worse.
dgant 16y ago
C++ lends itself to a large variety of different programming styles and paradigms. C++ also lends itself to premature baldness, by developers ripping their hair out trying to make systems developed in different styles interact with each other. A popular thought is that any given team or company should pick a particular subset of those styles -- and perhaps a subset of C++'s features -- and use them to the exclusion of others.
pkaler 16y ago
Kids these days with their allocations and virtual memory. shakes fist You don't need std::vector if you don't need dynamic memory allocations. Game programming and systems programming is a whole lot different than web or desktop development. For games, you create a memory budget up front. You decide how much memory sound, textures, models, AI will consume up front and then statically allocate that memory up front. http://gamesfromwithin.com/start-pre-allocating-and-stop-worrying http://gamesfromwithin.com/start-pre-allocating-and-stop-wor... You can statically allocate at the start of a game, level, and frame. From the original article: OpenAL appears to have a limit of 1024 sound buffers, which we bumped into. We could dynamically create and destroy the static buffer mappings without too much trouble, but that is a reasonable number for us to stay under. It also sounds like Carmack is loading an entire level as a memory mapped file and then doing reads into specific indexes within the file. Take a look at the source code that id has open sourced. That's the best way to get a feel how this style of development works. I believe RtCW is their last release. ftp://ftp.idsoftware.com/idstuff/source/ http://github.com/monoid/rtcw-rebirth http://github.com/monoid/rtcw-rebirth
- colkassad 16y ago
  Actually, I'm 38...bit of a late starter :) Thanks for the reply and link. Modeling and simulation is my area of interest (I work in civil and environmental engineering), so it will be interesting to see what patterns will work best.
edderly 16y ago
Google gives a good take on restrained C++: http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml http://google-styleguide.googlecode.com/svn/trunk/cppguide.x...
- colkassad 16y ago
  Nice, I read this a long time ago before learning C++. It's interesting (and reassuring) that some of the stuff we are learning is considered bad practice by Google.

tzs 16y ago

My C++ also tends to be simple. I also have never had a need for any formal "design patterns", as every time I've encountered a problem for which it turns out there is named pattern in the books, a few moments thought about the problem has always led me to discover the solution myself. Now, it could be that this means I'm some kind of programming genius. I wish that were true, but alas I think it is not so much a reflection of how good I am, but rather how mediocre many programmers are today.

aaronblohowiak 16y ago
"Design Patterns" exists to give a common vocabulary to the things we do with code and discuss the proper application of the techniques.

np3000 16y ago

Some more Carmack tweets on C++ IMO, good C++ code is better than good C code, but bad C++ can be much, much worse than bad C code. 10:17 AM Oct 6th I wish C++ had a "functional" qualifier to enforce no global references or side effects. 11:16 PM Sep 21st Reading More Effective C++. I have grown to appreciate at least some uses of most C++ features, but I still don't buy in on exceptions. 10:26 PM Aug 13th

dhess 16y ago
I'm no C++ fan (anymore), either, but I don't understand Carmack's taking exception with exceptions. If the alternative is guarding every function call with an if statement to check for error codes, I'll take exceptions almost every time. (Many game programmers I know think that checking for errors is usually bad game programming style, period, but I'm assuming Carmack isn't one of those people.) Exceptions do have possibly deleterious effects on performance, but then, you can just be judicious about where you use them. Exceptions are at least appropriate for catastrophic failures like, "Oops, the game just crashed," or, "Your network connection died." Thinking about manually unwinding out of a game-over failure like that makes me grimace. Sigh, game programmers. :)
- pkaler 16y ago
  Throwing an exception is a misnomer. An exception doesn't necessarily mean that an error happened. It means, "please unwind the call stack". Unwinding the call stack in a game is a no-no. Games, especially the simulation, must be deterministic. An exception would most likely destroy determinism. The simulation/AI is a big, hairy, ugly set of if/else and switch statements anyway. Adding extra error checking is not an extra burden. The visualization sends asynchronous commands from the CPU to the GPU. The error condition won't be known right away. Querying the GPU will cause a flush of your command stream and ruin performance. Dynamic memory allocation is reduced to a minimum during a frame so you don't get out of memory errors. Strings are allocated in a pool. Network sockets, file handles, and other performance intensive resources are not created mid-frame. Exceptions are not a win for games. It is usually best to run the entire frame and then check for errors all at once at the end.

dhess 16y ago

I'm on the same arc (especially the template Kool-Aid phase), except perhaps further along: now I forgo C++ entirely and write plain C because it's so much easier to wrap from higher-level languages. I do miss smart pointers, but on the other hand, dealing with malloc and friends keeps me honest about what really needs to be written in C.

acqq 16y ago
For the high performance stuff I write my kind of restrained C++: never STL in the interfaces of the "modules," use STL algorithms (they are good) but otherwise manage memory in custom ways (which is easier by not using STL containers!). But I had to solve one interesting problem using some recursive definitions and code, and discovered that once I "freed" the code from classes (made them C functions) I was able to express it properly -- just having them as members prevented me to see that the solution is much more obvious when you actually use plain pointers and don't think about the same "object" even during the life of the function. Add to that in the member "this" can't be null. When you need real expressiveness, C can't be beaten. C++ syntactic sugar helps sometimes, but limiting to it is... limiting!

sandGorgon 16y ago

Do you use STL then ? Because, that was pretty much the only reason I started using C++. Or do you write your own containers