Richard Cownie (tich@pobox.com) on 6/27/10 wrote:
---------------------------
>Even if you don't want the hassle of a fully distributed
>compile, now that you can easily get a server with 2 cpus,
>8 cores, and 16 threads, you should be able to get at
>least a 10x speedup with a parallel compile on a single
>machine. Unless your build system or your file IO is
>horribly screwed up.
The build system/dependencies being screwed up is part of the problem. I think.


>This isn't an argument for C++ - if build time is faster
>with Java, that's good - but I don't think what you see
>is inherent to C++.

Actually, I wasn't arguing that the Java build time was faster (although it was). I was arguing that Vincent's claim that very few developers had long/slow build times was rare was an unsubstantiated claim. I still think it is.

However, I also think that C++ inherently takes longer to build than equivalent Java. Two things *should* contribute to this:

(a) The C++ syntax is more complicated, and thus takes more effort to parse. I can't quantify this myself, but I don't think the difference is trivial.

(b) Because "#include" forces I/O and logically a re-parse of the included files (because how the #include parses has a dependency on what include files came first ... Java imports don't have this behavior), C++ should have more disk I/O (logically more, even if the file system caches in RAM) and more parsing of the same files. With cleverness and pre-compiled headers much of this can be mitigated, although back when I was paying more attention the C++ side didn't trust the pre-compiled headers ... they had been nailed by bugs introduced by them too many times, so they didn't use them.

And a third:

(c) Because of the different object models, the C++ can require a full recompile more often than the Java.


But ... basically, I'm arguing that Vincent's claim that slow compiles only effects a small percentage of developers in unfounded. It might, but I don't think Vincent *knows* this (any more than I do). I'd like to see data, if it exists.

-Mark Roulo