Re: GNU Parallel Bug Reports Wrong detection of CPUS or cores

[William Bader]

>From: Bug-parallel <bug-parallel-bounces+williambader=address@hidden> on behalf of Saint Michael <address@hidden>

>Sent: Thursday, October 3, 2019 9:27 PM
>To: bug-parallel <address@hidden>
>Subject: GNU Parallel Bug Reports Wrong detection of CPUS or cores

> 

>My box has 16 cores. 1 CPU.  Parallel thinks it has 2 cores. I realized this the hard way because if I use -j-4, it fails to run. If I use -j+0, it runs with 2 max jobs.

>What is the mechanism used by parallels to decide how many cores a machine has?

>I can see I have 16 cores with top and with cat /proc/cpuinfo.

>I don't want to tell Parallel how many jobs to run, I need that Parallel guesses right.

parallel caches the cpu count in ~/.parallel/tmp/sshlogin/<full-host-name>/cpuspec with the sockets, cores, and threads. Are the values in that file correct? Otherwise the code (in sub socket_core_thread()) depends a lot on the operating system and on the format of /proc/cpuinfo.