Matrix Multiplication in BLAS & CBLAS

Here is a program that uses dgemm to multiply two matrices:  matrix_mult.cpp

The dgemm function is implemented using gsl blas.

It can be compiled under Cygwin as:

gcc -o matrix_mult_alt matrix_mult_alt.cpp -lgsl -lstdc++

And under Ubuntu as:

gcc -o matrix_mult_alt matrix_mult_alt.cpp -lgsl -lgslcblas -lstdc++

* * *

For benchmark comparison, here is a matrix multiplication program which uses pure pointer access without BLAS.    matrix_11.cpp

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A Fortran program which uses the intrinsic function MATMUL is given at:  MATRIX_MULT.F

A Fortran program which uses DGEMM is:  MATRIX_MULT_D.F

The program was compiled using:

gfortran -o MATRIX_MULT_D MATRIX_MULT_D.F -lblas -llapack

As an aside, the following was used to determine memory leaks during the debugging process:

gfortran -g -o MATRIX_MULT_D MATRIX_MULT_D.F -lblas -llapack -Wall -fbounds-check -fmax-errors=1 -Werror

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Here is a program  matrix_mult_cblas.cpp  which uses cblas_dgemm.

It is compiled in Cygwin via:

gcc -o matrix_mult_cblas matrix_mult_cblas.cpp c:/cygwin/lib/libblas.a c:/cygwin/lib/libcygwin.a c:/cygwin/home/tirvine/CBLAS/lib/cblas_LINUX.a -lstdc++

The paths should be modified according to your library installation.

Note that CBLAS can be installed in Cygwin using the instructions at:

https://vibrationdata.wordpress.com/2011/11/07/install-cblas-in-ubuntu/

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Tom Irvine

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