From: Daniel Berger <djberg96@...>
Date: 2007-03-12T13:55:05+09:00
Subject: Re: Trying to make Array#collect massively parallel with OpenMP

On Mar 11, 4:37 pm, "Jan Svitok" <jan.svi...@gmail.com> wrote:
> On 3/11/07, Daniel Berger <djber...@gmail.com> wrote:
>
>
>
> > Hi all,
>
> > Windows XP Home
> > VC++ 8 (free edition)
>
> > Just for kicks I tried creating a parallel Array#collect method, which
> > I called Array#acollect (asynch. collect). I added the following C
> > code to array.c, rebuilt and reinstalled, but it doesn't seem to be
> > any faster. Could this be an issue with my compiler? Or a Windows
> > thing?
>
> > static VALUE rb_ary_acollect(VALUE ary){
> >    long i;
> >    VALUE collect;
>
> >    if (!rb_block_given_p())
> >            return rb_ary_new4(RARRAY(ary)->len, RARRAY(ary)->ptr);
>
> >    collect = rb_ary_new2(RARRAY(ary)->len);
>
> >    #pragma omp parallel for
> >       for (i = 0; i < RARRAY(ary)->len; i++)
> >          rb_ary_push(collect, rb_yield(RARRAY(ary)->ptr[i]));
>
> >    return collect;
> > }
>
> > rb_define_method(rb_cArray, "acollect", rb_ary_acollect, 0);
>
> > # bench_collect.rb
> > require "benchmark"
>
> > MAX = 4000
>
> > array = []
> > MAX.times{ |n|
> >    array[n] = 2 * n
> > }
>
> > # No significant difference (?)
> > Benchmark.bm(30) do |x|
> >    x.report("Array#collect"){
> >       MAX.times{ array.collect{ |e| e += 4 } }
> >    }
> >    x.report("Array#acollect"){
> >       MAX.times{ array.acollect{ |e| e += 4 } }
> >    }
> > end
>
> > Ideas?
>
> > Thanks,
>
> > Dan
>
> Hi,
>
> I'm no expert in either ruby internals or openmp. I've just a few
> ideas for you (though most of them will be obvious probably):
>
> 1.http://msdn2.microsoft.com/en-us/library/fw509c3b(VS.80).aspxsays
> you need to add /openmp compiler switch (try using _OPENMP define to
> see if the compiler recognizes omp pragmas). #include "omp.h" might
> help as well.

Ah, thanks. I tried that and I got:

LINK : fatal error LNK1104: cannot open file 'VCOMP.lib'

It doesn't look like I have omp.h. This may be a header that's not
included in the free version of VC++. I'll have to ask around.

Thanks,

Dan