###############################################################################
## ----------------------------------------------------------------------------
## MCE::Util - Public and private utility functions for Many-Core Engine.
##
###############################################################################

package MCE::Util;

use strict;
use warnings;

## no critic (BuiltinFunctions::ProhibitStringyEval)

use base qw( Exporter );
use bytes;

our $VERSION = '1.521';

our @EXPORT_OK = qw( get_ncpu );
our %EXPORT_TAGS = ( all => \@EXPORT_OK );

###############################################################################
## ----------------------------------------------------------------------------
## The get_ncpu subroutine, largely adopted from Test::Smoke::Util.pm,
## returns the number of logical (online/active/enabled) CPU cores;
## never smaller than one.
##
## A warning is emitted to STDERR when it cannot recognize the operating
## system or the external command failed.
##
###############################################################################

my $g_ncpu;

sub get_ncpu {

   return $g_ncpu if (defined $g_ncpu);

   local $ENV{PATH} = "/usr/sbin:/sbin:/usr/bin:/bin:$ENV{PATH}";
   $ENV{PATH} =~ /(.*)/; $ENV{PATH} = $1;   ## Remove taintedness

   my $ncpu = 1;

   OS_CHECK: {
      local $_ = lc $^O;

      /linux/ && do {
         my ($count, $fh);
         if ( open $fh, '<', '/proc/stat' ) {
             $count = grep { /^cpu\d/ } <$fh>;
             close $fh;
         }
         $ncpu = $count if $count;
         last OS_CHECK;
      };

      /bsd|darwin|dragonfly/ && do {
         chomp( my @output = `sysctl -n hw.ncpu 2>/dev/null` );
         $ncpu = $output[0] if @output;
         last OS_CHECK;
      };

      /aix/ && do {
         my @output = `pmcycles -m 2>/dev/null`;
         if (@output) {
            $ncpu = scalar @output;
         } else {
            @output = `lsdev -Cc processor -S Available 2>/dev/null`;
            $ncpu = scalar @output if @output;
         }
         last OS_CHECK;
      };

      /gnu/ && do {
         chomp( my @output = `nproc 2>/dev/null` );
         $ncpu = $output[0] if @output;
         last OS_CHECK;
      };

      /hp-?ux/ && do {
         my $count = grep { /^processor/ } `ioscan -fkC processor 2>/dev/null`;
         $ncpu = $count if $count;
         last OS_CHECK;
      };

      /irix/ && do {
         my @out = grep { /\s+processors?$/i } `hinv -c processor 2>/dev/null`;
         $ncpu = (split ' ', $out[0])[0] if @out;
         last OS_CHECK;
      };

      /osf|solaris|sunos|svr5|sco/ && do {
         if (-x '/usr/sbin/psrinfo') {
            my $count = grep { /on-?line/ } `psrinfo 2>/dev/null`;
            $ncpu = $count if $count;
         }
         else {
            my @output = grep { /^NumCPU = \d+/ } `uname -X 2>/dev/null`;
            $ncpu = (split ' ', $output[0])[2] if @output;
         }
         last OS_CHECK;
      };

      /mswin|mingw|cygwin/ && do {
         if (exists $ENV{NUMBER_OF_PROCESSORS}) {
            $ncpu = $ENV{NUMBER_OF_PROCESSORS};
         }
         last OS_CHECK;
      };

      warn "MCE::Util::get_ncpu: command failed or unknown operating system\n";
   }

   $ncpu = 1 if (!$ncpu || $ncpu < 1);

   return $g_ncpu = $ncpu;
}

###############################################################################
## ----------------------------------------------------------------------------
## Private methods.
##
###############################################################################

sub _parse_max_workers {

   my ($_max_workers) = @_;

   return $_max_workers unless (defined $_max_workers);

   if ($_max_workers =~ /^auto(?:$|\s*([\-\+\/\*])\s*(.+)$)/i) {
      my ($_ncpu_ul, $_ncpu);

      $_ncpu_ul = $_ncpu = get_ncpu();
      $_ncpu_ul = 8 if ($_ncpu_ul > 8);

      if ($1 && $2) {
         local $@; $_max_workers = eval "int($_ncpu_ul $1 $2 + 0.5)";
         $_max_workers = 1 if (!$_max_workers || $_max_workers < 1);
         $_max_workers = $_ncpu if ($_max_workers > $_ncpu);
      }
      else {
         $_max_workers = $_ncpu_ul;
      }
   }

   return $_max_workers;
}

sub _parse_chunk_size {

   my ($_chunk_size, $_max_workers, $_params, $_input_data, $_array_size) = @_;

   return $_chunk_size if (!defined $_chunk_size || !defined $_max_workers);

   if (defined $_params && exists $_params->{chunk_size}) {
      $_chunk_size = $_params->{chunk_size};
   }

   if ($_chunk_size =~ /([0-9\.]+)K\z/i) {
      $_chunk_size = int($1 * 1024 + 0.5);
   }
   elsif ($_chunk_size =~ /([0-9\.]+)M\z/i) {
      $_chunk_size = int($1 * 1024 * 1024 + 0.5);
   }

   if ($_chunk_size eq 'auto') {
      my $_size = (defined $_input_data && ref $_input_data eq 'ARRAY')
         ? scalar @{ $_input_data } : $_array_size;

      my $_is_file;

      if (defined $_params && exists $_params->{sequence}) {
         my ($_begin, $_end, $_step);

         if (ref $_params->{sequence} eq 'HASH') {
            $_begin = $_params->{sequence}->{begin};
            $_end   = $_params->{sequence}->{end};
            $_step  = $_params->{sequence}->{step} || 1;
         }
         else {
            $_begin = $_params->{sequence}->[0];
            $_end   = $_params->{sequence}->[1];
            $_step  = $_params->{sequence}->[2] || 1;
         }

         if (!defined $_input_data && !$_array_size) {
            $_size = abs($_end - $_begin) / $_step + 1;
         }
      }
      elsif (defined $_params && exists $_params->{_file}) {
         my $_ref = ref $_params->{_file};

         if ($_ref eq 'SCALAR') {
            $_size = length ${ $_params->{_file} };
         } elsif ($_ref eq '') {
            $_size = -s $_params->{_file};
         } else {
            $_size = 0; $_chunk_size = 245_760;
         }

         $_is_file = 1;
      }
      elsif (defined $_input_data) {
         if (ref $_input_data eq 'GLOB' || ref($_input_data) =~ /^IO::/) {
            $_is_file = 1; $_size = 0; $_chunk_size = 245_760;
         }
         elsif (ref $_input_data eq 'SCALAR') {
            $_is_file = 1; $_size = length ${ $_input_data };
         }
      }

      if (defined $_is_file) {
         if ($_size) {
            $_chunk_size = int($_size / $_max_workers / 24 + 0.5);
            $_chunk_size = 4_194_304 if $_chunk_size > 4_194_304;  ## 4M
            $_chunk_size = 2 if $_chunk_size <= 8192;
         }
      }
      else {
         $_chunk_size = int($_size / $_max_workers / 24 + 0.5);
         $_chunk_size = 8000 if $_chunk_size > 8000;
         $_chunk_size = 2 if $_chunk_size < 2;
      }
   }

   return $_chunk_size;
}

1;

__END__

###############################################################################
## ----------------------------------------------------------------------------
## Module usage.
##
###############################################################################

=head1 NAME

MCE::Util - Public and private utility functions for Many-Core Engine

=head1 VERSION

This document describes MCE::Util version 1.521

=head1 SYNOPSIS

 use MCE::Util;

=head1 DESCRIPTION

A utility module for MCE. Nothing is exported by default. Exportable is
get_ncpu.

=head2 get_ncpu()

Returns the number of logical (online/active/enabled) CPU cores; never smaller
than one.

 my $ncpu = MCE::Util::get_ncpu();

Specifying 'auto' for max_workers calls MCE::Util::get_ncpu automatically.
MCE 1.521 sets an upper-limit when specifying 'auto'. The reason is mainly
to safeguard apps from spawning 100 workers on a box having 100 cores.
This is important for apps which are IO-bound.

 use MCE;

 ## 'Auto' is the total # of logical cores (lcores) (8 maximum, MCE 1.521)
 ## The computed value will not exceed the # of logical cores on the box.

 my $mce = MCE->new(

   max_workers => 'auto',       ##  1 on HW with 1-lcores;  2 on  2-lcores
   max_workers =>  16,          ## 16 on HW with 4-lcores; 16 on 32-lcores

   max_workers => 'auto',       ##  4 on HW with 4-lcores;  8 on 16-lcores
   max_workers => 'auto*1.5',   ##  4 on HW with 4-lcores; 12 on 16-lcores
   max_workers => 'auto*2.0',   ##  4 on HW with 4-lcores; 16 on 16-lcores
   max_workers => 'auto/2.0',   ##  2 on HW with 4-lcores;  4 on 16-lcores
   max_workers => 'auto+3',     ##  4 on HW with 4-lcores; 11 on 16-lcores
   max_workers => 'auto-1',     ##  3 on HW with 4-lcores;  7 on 16-lcores

   max_workers => MCE::Util::get_ncpu,   ## run on all lcores
 );

In summary:

 1. Auto has an upper-limit of 8 in MCE 1.521 (# of lcores, 8 maximum)
 2. Math can be applied with auto (*/+-) to change the upper limit
 3. The computed value for auto will not exceed the total # of lcores
 4. One can specify max_workers explicity to a hard value
 5. MCE::Util::get_ncpu returns the actual # of lcores

=head1 ACKNOWLEDGEMENTS

The portable code for detecting the number of processors was adopted from
L<Test::Smoke::SysInfo|Test::Smoke::SysInfo>.

=head1 INDEX

L<MCE|MCE>

=head1 AUTHOR

Mario E. Roy, S<E<lt>marioeroy AT gmail DOT comE<gt>>

=head1 LICENSE

This program is free software; you can redistribute it and/or modify it
under the terms of either: the GNU General Public License as published
by the Free Software Foundation; or the Artistic License.

See L<http://dev.perl.org/licenses/> for more information.

=cut

