matrix multiplication

matrix multiplication

[Matthew J. Doller]

someone correct me if i am wrong, but is there really no way of
multiplying two matrices, or a matrix and a vector with gsl
i know i can go element by element, but i'm looking for something of the
form:

return_matrix = gsl_matrix_mul_matrix_by_matrix ( matrix_one ,
matrix_two );

thanks!
matt

-- 
Matthew J. Doller 
mdoller@wpi.edu
http://www.wpi.edu/~mdoller

Re: matrix multiplication

[Dan, Ho-Jin]

[-- Attachment #1: Type: text/plain, Size: 483 bytes --]

try to use level 3 of blas.
gsl supports blas interfaces. A simple example is attatched. gsl_gemm.c
LDFLAGS=-lgsl -lgslcblas -lm
yours
Dan, Ho-Jin

Matthew J. Doller wrote:

>someone correct me if i am wrong, but is there really no way of
>multiplying two matrices, or a matrix and a vector with gsl
>i know i can go element by element, but i'm looking for something of the
>form:
>
>return_matrix = gsl_matrix_mul_matrix_by_matrix ( matrix_one ,
>matrix_two );
>
>thanks!
>matt
>



[-- Attachment #2: gsl_gemm.c --]
[-- Type: text/plain, Size: 652 bytes --]

#include <stdio.h>
#include <gsl/gsl_matrix.h>
#include <gsl/gsl_blas.h>

int main()
{
  double A[] = { 
    1., 2., 
    3., 4. 
  };
  double B[] = {
    2., 3.,
    4., 5.
  };
  double alpha = 1., beta = 0.;

  gsl_matrix_view A_m = gsl_matrix_view_array(A, 2, 2);
  gsl_matrix_view B_m = gsl_matrix_view_array(B, 2, 2);
  gsl_matrix *C = gsl_matrix_alloc(2,2);

  gsl_blas_dgemm(CblasNoTrans, CblasNoTrans, alpha, &A_m.matrix, 
      &B_m.matrix, beta, C);

  printf("[[\n%f\t%f\n%f\t%f]]\n", 
      gsl_matrix_get(C, 0, 0), gsl_matrix_get(C, 0, 1), 
      gsl_matrix_get(C, 1, 0), gsl_matrix_get(C, 1, 1));

  gsl_matrix_free(C);
  return 0;
}

matrix multiplication

[Matthew J. Doller]

someone correct me if i am wrong, but is there really no way of
multiplying two matrices, or a matrix and a vector with gsl
i know i can go element by element, but i'm looking for something of the
form:

return_matrix = gsl_matrix_mul_matrix_by_matrix ( matrix_one ,
matrix_two );

thanks!
matt

-- 
Matthew J. Doller 
mdoller@wpi.edu
http://www.wpi.edu/~mdoller

Re: matrix multiplication

[Dan, Ho-Jin]

try to use level 3 of blas.
gsl supports blas interfaces. A simple example is attatched. gsl_gemm.c
LDFLAGS=-lgsl -lgslcblas -lm
yours
Dan, Ho-Jin

Matthew J. Doller wrote:

>someone correct me if i am wrong, but is there really no way of
>multiplying two matrices, or a matrix and a vector with gsl
>i know i can go element by element, but i'm looking for something of the
>form:
>
>return_matrix = gsl_matrix_mul_matrix_by_matrix ( matrix_one ,
>matrix_two );
>
>thanks!
>matt
>

Re: matrix multiplication

[Dan, Ho-Jin]

[-- Attachment #1: Type: text/plain, Size: 483 bytes --]

try to use level 3 of blas.
gsl supports blas interfaces. A simple example is attatched. gsl_gemm.c
LDFLAGS=-lgsl -lgslcblas -lm
yours
Dan, Ho-Jin

Matthew J. Doller wrote:

>someone correct me if i am wrong, but is there really no way of
>multiplying two matrices, or a matrix and a vector with gsl
>i know i can go element by element, but i'm looking for something of the
>form:
>
>return_matrix = gsl_matrix_mul_matrix_by_matrix ( matrix_one ,
>matrix_two );
>
>thanks!
>matt
>



[-- Attachment #2: gsl_gemm.c --]
[-- Type: text/plain, Size: 652 bytes --]

#include <stdio.h>
#include <gsl/gsl_matrix.h>
#include <gsl/gsl_blas.h>

int main()
{
  double A[] = { 
    1., 2., 
    3., 4. 
  };
  double B[] = {
    2., 3.,
    4., 5.
  };
  double alpha = 1., beta = 0.;

  gsl_matrix_view A_m = gsl_matrix_view_array(A, 2, 2);
  gsl_matrix_view B_m = gsl_matrix_view_array(B, 2, 2);
  gsl_matrix *C = gsl_matrix_alloc(2,2);

  gsl_blas_dgemm(CblasNoTrans, CblasNoTrans, alpha, &A_m.matrix, 
      &B_m.matrix, beta, C);

  printf("[[\n%f\t%f\n%f\t%f]]\n", 
      gsl_matrix_get(C, 0, 0), gsl_matrix_get(C, 0, 1), 
      gsl_matrix_get(C, 1, 0), gsl_matrix_get(C, 1, 1));

  gsl_matrix_free(C);
  return 0;
}

Re: matrix multiplication

[Brian Gough]

Daniel T Konkle writes:
 >  I need to implement S = A' * A where A' is the transpose of A.
 >  Is it possible to do it like this:
 >  gsl_blas_dgemm( CblasTrans, CblasNoTrans, 1.0, A, A, 0.0, S );
 >  or do I need to copy the contents of a into a temporary matrix
 > first
 >  gsl_matrix_memcpy( B, A ); gsl_blas_dgemm( CblasTrans,
 > CblasNoTrans, 1.0, A, B, 0.0, S );

If you look at the function definition in the gsl_blas.h header file
or the manual the 'const' keyword shows which arguments are not
modified.

regards
Brian Gough

matrix multiplication

[Daniel T Konkle]

I need to implement  S = A' * A  where A' is the transpose of A.

Is it possible to do it like this:

gsl_blas_dgemm( CblasTrans, CblasNoTrans, 1.0, A, A, 0.0, S );

or do I need to copy the contents of a into a temporary matrix first

gsl_matrix_memcpy( B, A );
gsl_blas_dgemm( CblasTrans, CblasNoTrans, 1.0, A, B, 0.0, S );

Thanks,
Danny