RE: external BLAS library with gfortran 4.1 or 4.4 on rhel5

[Matthew Hobbs <matthew dot hobbs at sydney dot edu dot au>]

Thanks you so much for replying to me. Here is some more information.

Firstly, I am using a test fortran 90 program called matmultest.f90 which just does a single matmul operation. On a fedora 15 system (my laptop) I can see a definite increase in speed if I use an external blas library:

# ----------------------------------
# fedora system:

matrix: gfortran --version
GNU Fortran (GCC) 4.6.0 20110603 (Red Hat 4.6.0-10)

gfortran matmultest.f90 -o matmultest
gfortran -L/usr/lib/atlas -fexternal-blas -lblas matmultest.f90 -o matmultest_blas
gfortran -L/usr/lib/atlas -fexternal-blas -lf77blas matmultest.f90 -o matmultest_f77blas

#baseline:
time ./matmultest

real	0m13.853s
user	0m13.759s
sys	0m0.066s

#no speed up here (why?):
time ./matmultest_blas

real	0m13.883s
user	0m13.701s
sys	0m0.126s

#but this is good:
time ./matmultest_f77blas 

real	0m7.663s
user	0m7.595s
sys	0m0.060s
# ----------------------------------

So I try achieving the same sort of thing with the test program on my RHEL5 system:

gfortran --version
GNU Fortran (GCC) 4.1.2 20080704 (Red Hat 4.1.2-52)

gfortran matmultest.f90 -o matmultest

time ./matmultest

real	0m33.158s
user	0m33.074s
sys	0m0.075s

gfortran -L/usr/lib64/atlas -fexternal-blas -lf77blas matmultest.f90 -o matmultest_f77blas
f951: error: unrecognized command line option "-fexternal-blas"

SInce this version of gfortran doesn't have the required option, try gfortran44:

gfortran44 -L/usr/lib64/atlas -fexternal-blas -lf77blas matmultest.f90 -o matmultest_f77blas
/usr/bin/ld: warning: libgfortran.so.1, needed by /usr/lib64/atlas/libf77blas.so, may conflict with libgfortran.so.3

My vague understanding of this is that /usr/lib64/atlas/libf77blas.so was not built with gfortran 4.4 and so can't be used by my gfortran44 program in this way.

The epel repo is enabled and the packages you suggest are installed:

Installed Packages
Name       : atlas
Arch       : x86_64
Version    : 3.8.3
Release    : 1.el5
Size       : 11 M
Repo       : installed

Name       : atlas-devel
Arch       : x86_64
Version    : 3.8.3
Release    : 1.el5
Size       : 23 M
Repo       : installed

Hope that clarifies my problem.

I look forward to hearing back from you (or anyone else kind enough to help!)

Thanks again,

Matthew


________________________________________
From: Shakthi Kannan [shakthimaan@gmail.com]
Sent: Wednesday, March 14, 2012 4:39 PM
To: Matthew Hobbs
Cc: gcc-help@gcc.gnu.org
Subject: Re: external BLAS library with gfortran 4.1 or 4.4 on rhel5

Hi Matthew:

--- On Wed, Mar 14, 2012 at 8:12 AM, Matthew Hobbs
<matthew.hobbs@sydney.edu.au> wrote:
| I cannot find any RHEL5 package that provides an
| external BLAS library that can be used with this version (correct me
if I'm wrong).
| I have tried installing netlib blas, atlas, goto2 from source to
| get something that will work
\--

Can you try the atlas, atlas-devel packages from the EPEL repo?

  http://fedoraproject.org/wiki/EPEL

  http://dl.fedoraproject.org/pub/epel/5/x86_64/repoview/letter_a.group.html

SK

--
Shakthi Kannan
http://www.shakthimaan.com