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List: gcc-fortran
Subject: [gomp] omp performance question
From: "Daniel Franke" <franke.daniel () gmail ! com>
Date: 2006-10-30 16:38:57
Message-ID: 640ad44b0610300838t9b22dabyf6c0a97342fb63c6 () mail ! gmail ! com
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2006/10/30, François-Xavier Coudert <fxcoudert@gmail.com>:
> > single threaded ( FCFLAGS=-O1) timings on x64_64, dual CPU (dual core
> > each), gave:
> > real 64m36.502s
> > user 64m36.886s
> > sys 0m0.040s
> >
> > same machine, OMP enabled (FCFLAGS="-O1 -fopenmp"):
> > real 67m16.611s
> > user 112m22.885s
> > sys 25m44.641s
>
> What is OMP_NUM_THREADS set to?
The numbers above use the default implementation without setting
OMP_NUM_THREADS explicitely. Letting OMP_NUM_THREADS=4, i.e. the
number of cores available, results are:
OMP_NUM_THREADS=4, OMP_DYNAMIC=[DEFAULT]
real 59m47.223s
user 91m33.127s
sys 24m35.856s
OMP_NUM_THREADS=4, OMP_DYNAMIC=FALSE
real 57m36.233s
user 91m59.685s
sys 26m31.735s
Some more timings (same machine):
OMP_NUM_THREADS=4, OMP_DYNAMIC=TRUE
IN PROGRESS
(ps -efL shows four threads running)
OMP_NUM_THREADS=8, OMP_DYNAMIC=TRUE
real 168m46.983s
user 97m53.903s
sys 113m0.108s
(ps -efL showed three threads actually running)
OMP_NUM_THREADS=8, OMP_DYNAMIC=FALSE
real 85m54.649s
user 125m20.442s
sys 48m15.253s
I'll try to add some numbers from ia64 (8CPU) if I can get exclusive hold of it.
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