From: Daniel Berger <djberg96@...>
Date: 2007-03-12T05:10:05+09:00
Subject: Trying to make Array#collect massively parallel with OpenMP

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