Update: It is -fopenmp that isn't mentioned in any files under the _Inline/build directory, not -lgomp.

Inline::C is ignoring -fopenmp, which causes warnings behind the scene stating the pragma omp is unknown. This can be seen by specifying BUILD_NOISY and CLEAN_AFTER_BUILD. Afterwards, I look inside the _Inline/build directory and was unable to find -fopenmp mentioned anywhere inside the log files. The -lgomp was there though.

use Inline 'C' => Config => BUILD_NOISY => 1;
use Inline 'C' => Config => CCFLAGSEX => '-O3 -fopenmp';
use Inline 'C' => config => LIBS => '-lgomp';
use Inline 'C' => <<'END_C',  CLEAN_AFTER_BUILD => 0;
   // C code
END_C
[download]

Parallel is possible nonetheless and saw many cores computing simultaneously. The serial code takes 12.4 seconds with parallel completing in 3 seconds on a CentOS 7 VM configured with 4 real cores.

#!/usr/bin/env perl
use strict;
use warnings;

use Inline 'C' => Config => CCFLAGSEX => '-O3';
use Inline 'C' => <<'END_C';

#include <stdio.h>
#include <stdlib.h>

int escapes(
    double cr, double ci, int it
) {
  double zr = 0;
  double zi = 0;
  double zrtmp;
  int i;

  for(i=0; i<it; i++) {
    // z <- z^2 + c
    zrtmp = zr*zr - zi*zi + cr;
    zi = 2*zr*zi + ci;
    zr = zrtmp;
    if (zr*zr + zi*zi > 4) {
      return 1;
    }
  }

  return 0;
}

SV* mandel(
    int yc_beg, int yc_end,
    double xmin, double xmax, int xstep,
    double ymin, double ymax, int ystep,
    int iters
) {
  int yc, len;
  SV *buf = newSVpvn("", 0);

  // array of string to store result
  char *m = (char *) malloc(ystep * (xstep + 1) * sizeof(char));

  for(yc = yc_beg; yc <= yc_end; yc++) {
    double y = yc*(ymax-ymin)/ystep + ymin;
    int xc;
    for(xc=0; xc<xstep; xc++) {
      double x = xc*(xmax-xmin)/xstep + xmin;
      escapes(x, y, iters);
      if (escapes(x, y, iters)) {
        m[yc * (xstep + 1) + xc] = ' ';
      } else {
        m[yc * (xstep + 1) + xc] = 'X';
      }
    }
    // add end of string
    m[yc * (xstep+1) + xstep] = '\0';
  }

  for(yc=yc_beg; yc<=yc_end; yc++) {
    sv_catpv(buf, (char *) &m[yc * (xstep+1)]);
    sv_catpv(buf, (char *) "\n");
  }

  free(m);

  return sv_2mortal(buf);
}

END_C

use MCE::Flow;
use MCE::Candy;

MCE::Flow::init(
   bounds_only => 1, max_workers => $ENV{'MCE_NUM_THREADS'} || 'auto',
   gather => MCE::Candy::out_iter_fh(\*STDOUT)
);

mce_flow_s sub {
  my ($mce, $sequence_ref, $chunk_id) = @_;
  my ($yc_beg, $yc_end) = @$sequence_ref;

  my $buf = mandel($yc_beg, $yc_end, -2.0, 1.0, 256, -1.0, 1.0, 256, 1
+00000);

  MCE->gather($chunk_id, $buf);

}, 0, 255;
[download]

Output order is required and handled by MCE::Candy::out_iter_fh. The output files are identical between C + OpenMP and Inline::C + MCE.

Sincerely, Mario

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