Re: Parallel extensions and Boost

[Marc Glisse <marc dot glisse at normalesup dot org>]

Hello,

On Mon, 20 Jul 2009, Dmitriy Morozov wrote:

> I am trying to compile a program that uses Boost libraries with GCC's
> parallel extensions, but I get linking errors. In particular, if I
> compile without the flags "-fopenmp -D_GLIBCXX_PARALLEL", then
> everything works fine. However, if I add those two flags, I get the
> error below. Actually, to be specific the error appears when I add
> -D_GLIBCXX_PARALLEL, -fopenmp by itself does not cause problems. I
> suspect the problem comes from the fact that Boost was compiled
> without -D_GLIBCXX_PARALLEL.

Indeed, as documented here:
http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt12ch31s03.html
"therefore one can only link code compiled with parallel mode and code 
compiled without parallel mode if no instantiation of a container is 
passed between the two translation units."
and the error message shows a vector.

> I was wondering if there was a way to
> work around this problem, since in this example I don't need the
> parallel extensions in the part of the code that uses Boost (in this
> case just for command line parsing).

You could separate the code that does the option parsing and the rest in 2 
separate files, one compiled with the parallel flag and one without it, 
such that no container is shared by the 2 parts. Or you could explicitly 
use parallel containers/algorithms where you want them so you don't need 
the global flag.

You could likely get away with a simple renaming of symbols, but it is 
unsupported.

--
Marc Glisse