MCE::Util(3) User Contributed Perl Documentation MCE::Util(3)
NAME
MCE::Util - Utility functions
VERSION
This document describes MCE::Util version 1.843
SYNOPSIS
use MCE::Util;
DESCRIPTION
A utility module for MCE. Nothing is exported by default. Exportable is
get_ncpu.
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 may 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 explicitly to a hard value
5. MCE::Util::get_ncpu returns the actual # of lcores
ACKNOWLEDGMENTS
The portable code for detecting the number of processors was adopted
from Test::Smoke::SysInfo.
INDEX
MCE(3), MCE::Core(3)
AUTHOR
Mario E. Roy, <marioeroyA ATA gmailA DOTA com>
perl v5.28.2 2019-07-24 MCE::Util(3)
mce 1.843.0 - Generated Tue Aug 6 13:34:56 CDT 2019