#!/usr/bin/perl -w
# $Id: njobihtm 1089 2018-12-19 10:45:41Z mueller $
#
# Copyright 2016-2018 by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>
#
# This program is free software; you may redistribute and/or modify it under
# the terms of the GNU General Public License as published by the Free
# Software Foundation, either version 3, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY, without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
# for complete details.
#
#  Revision History:
# Date         Rev Version  Comment
# 2018-12-18  1089   1.0.1  add and use bailout
# 2016-10-01   810   1.0    Initial version
#

use 5.14.0;                                 # require Perl 5.14 or higher
use strict;                                 # require strict checking

use Getopt::Long;

my %opts = ();

GetOptions(\%opts, "verbose", "mem=s"
          )
  or bailout("bad command options");

my $ncpu;
my $ntpc;
my $nkb;
my $njob = 1;

get_cpuinfo();
get_meminfo();

bailout("failed to obtain cpu or mem size")
  unless (defined $ncpu && defined $ntpc && defined $nkb);

my $ncore = $ncpu / $ntpc;                  # number of cores
my $nht   = $ncpu - $ncore;

$njob = $ncore + int($nht/4);

if ($opts{verbose}) {
  printf STDERR "#cpus:        %d\n", $ncpu;
  printf STDERR "#thread/cpu:  %d\n", $ntpc;
  printf STDERR "#cores:       %d\n", $ncore;
  printf STDERR "mem(MB):      %d\n", int($nkb/1024);
  printf STDERR "#job (cpus):  %d\n", $njob;
}

if (defined $opts{mem}) {
  my $mem;
  if ($opts{mem} =~ m/^(\d+)([MG])$/) {
    $mem =       1024 * $1 if $2 eq 'M';
    $mem = 1024* 1024 * $1 if $2 eq 'G';
    my $njobm = int(($nkb - 1024*1024) / $mem);
    $njobm = 1 unless $njobm > 0;
    printf STDERR "#job (mem):   %d\n", $njobm if $opts{verbose};
    if ($njobm < $njob) {
      $njob = $njobm;
    }
  } else {
    bailout("bad -mem option '$opts{mem}', must be nnn[MG]");
  }
}

print "$njob\n";

exit 0;

#-------------------------------------------------------------------------------
sub get_cpuinfo {
  open (LSCPU, "lscpu|")
    or bailout("failed to open 'lscpu|': $!");

  while (<LSCPU>) {
    chomp;
    if (m/^(.*?)\s*:\s*(.*)$/) {
      my $tag = $1;
      my $val = $2;
      # print "+++1 '$tag' : '$val' \n";
      $ncpu = $val if $tag eq 'CPU(s)';
      $ntpc = $val if $tag eq 'Thread(s) per core';
    }
  }
  close LSCPU;
  return;
}

#-------------------------------------------------------------------------------
sub get_meminfo {
  open (MEMINFO, "/proc/meminfo")
    or bailout("failed to open '/proc/meminfo': $!");

  while (<MEMINFO>) {
    chomp;
    if (m/^(.*?)\s*:\s*(\d+)\s*kB/) {
      my $tag = $1;
      my $val = $2;
      # print "+++1 '$tag' : '$val' \n";
      $nkb = $val if $tag eq 'MemTotal';
    }
  }
  close MEMINFO;
  return;
}

#-------------------------------------------------------------------------------

sub bailout {
  my ($msg) = @_;
  print STDERR "njobihtm-F: $msg\n";
  exit 1;
}