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[gomp] omp performance question
- From: "Daniel Franke" <franke dot daniel at gmail dot com>
- To: fortran at gcc dot gnu dot org
- Cc: "François-Xavier Coudert" <fxcoudert at gmail dot com>
- Date: Mon, 30 Oct 2006 17:38:57 +0100
- Subject: [gomp] omp performance question
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- References: <640ad44b0610300309u3e7f167fq62d2ec530766564a@mail.gmail.com> <19c433eb0610300331kd04cff5j340e84411d9f8fc@mail.gmail.com> <640ad44b0610300533y15a17e9fo2295cf662ff68a3b@mail.gmail.com>
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.