On Thu, 23 Apr 2015, Tim Prince wrote:
On 4/23/2015 10:25 AM, Marc Glisse wrote:
On Thu, 23 Apr 2015, Tim Prince wrote:
From the looks of gcc 6.0, it appears that gnu_parallel STL is slated to
become part of the release.
Could you be more specific about what you are talking about and where
you got your information?
I set -D_GLIBCXX_PARALLEL in previous versions but nothing happened.
According to
https://gcc.gnu.org/onlinedocs/libstdc++/manual/parallel_mode_using.html
something like "-fopenmp -O2 -D_GLIBCXX_PARALLEL" should work. And indeed
the generated code is quite different than without -D_GLIBCXX_PARALLEL. I
did not test performance.
Now in 6.0 it goes parallel, but with poor performance.
What other version are you comparing to? I would be very surprised if
anything had changed between 5.1.0 and current trunk (6.0).
Parallel mode has been a part of libstdc++ for several years:
https://gcc.gnu.org/onlinedocs/libstdc++/manual/parallel_mode.html
Am I right in believing that gnu_parallel STL code is not simd
vectorized?
It is not manually vectorized, but the compiler is free to do it if it
can.
Does this require setting -march and/or -ftree-vectorize options for
libstdc++ build? What would be the recommended incantation?
No, the compiled part of the library should not matter, it is only when
compiling your application that you should use -O3 -march=native to
maximize vectorization opportunities.
--
Marc Glisse
