Re: What has C++ become?
On Jun 9, 9:59 pm, Walter Bright <wal...@digitalmars-nospamm.com>
wrote:
Ian Collins wrote:
James Kanze wrote:
On Jun 8, 10:58 pm, Walter Bright <wal...@digitalmars-nospamm.com>
wrote:
Ian Collins wrote:
On my last couple of C++ projects, I was fortunate to enough to be
responsible for both the build farm design and budget as well as the
software design. So neither problem arose :)
Wow, I didn't know people actually used build farms for C++!
How many lines of code was that?
And how many different versions does he need? If you have
separate debug and release versions, for each program, on each
target platform, you can easily end up with ten or fifteen
complete builds. And with enough templates in the header files,
it doesn't take very many lines of source code (less than a
million, even) to end needed a build farm, just to be able to do
a clean build over the week-end.
This project was about 300K lines including tests. A
distributed clean build (which included a code generation
phase) took about 12 minutes, which was too long (10 was the
design limit). Any longer and productivity would have been
hit enough to add another node.
I've looked into trying to make the C++ compiler multithreaded
(so it could use multi core computers) many times. There just
isn't any way to do it, compiling C++ is fundamentally a
sequential operation. The only thing you can do is farm out
the separate source files for separate builds. The limit
achievable there is when there is one node per source file.
The input must be scanned sequentially, I'm pretty sure, since a
#define along the way can clearly affect how the following
source is read. And I rather suspect that it must also be
parsed sequentially, since the grammar is not context
free---whether a symbol is the name of a type, the name of a
template, or something else, affects parsing. But once you've
got your parse trees, couldn't you parallelize the processing of
each function: low-level optimization and code generation?
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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