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@xxxxxxxxx] Sent: Wednesday, March 14, 2012 4:39 PM To: Matthew Hobbs Cc: gcc-help@xxxxxxxxxxx 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@xxxxxxxxxxxxx> 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
