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Behavior of --use-cpus-instead-of-cores

From: Joe Sapp
Subject: Behavior of --use-cpus-instead-of-cores
Date: Tue, 17 Apr 2018 14:38:48 -0400

The option --use-cpus-instead-of-cores causes Parallel to count the
number of physical sockets on the machine instead of what some might
call the number of physical CPUs (what lscpu calls "cores" -- there is
varied use of terminology out there).  Without this option, as
expected, Parallel counts the number of CPUs, virtual or not (what
lscpu calls "CPUs").  If these are the intended behaviors, disregard

It seems the intention of this option was to only allow using up to
the number of CPUs with independent resources (i.e., disregard virtual
CPU technologies like hyperthreading).  I think then the number of
CPUs should be determined as the number of physical cores on each
socket times the number of sockets, like `lscpu -p | egrep -v '^#' |
sort -u -t, -k 2,4 | wc -l` [1].  If so, it seems there is an easy fix
for GNU/Linux; a patch to do so is attached.

Joe Sapp


Attachment: 00-phys-cpu-not-sockets.patch
Description: Binary data

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