HPL_dgemv man page

HPL_dgemv — y := beta * y + alpha * op(A) * x.

Synopsis

#include "hpl.h"
 void HPL_dgemv( const enum HPL_ORDER ORDER, const enum HPL_TRANS TRANS, const int M, const int N, const double ALPHA, const double * A, const int LDA, const double * X, const int INCX, const double BETA, double * Y, const int INCY );

Description

HPL_dgemv performs one of the matrix-vector operations

   y := alpha * op( A ) * x + beta * y,

where op( X ) is one of

   op( X ) = X   or   op( X ) = X^T.
 where alpha and beta are scalars, x and y are vectors and  A  is an m by n matrix.

Arguments

ORDER   (local input)           const enum HPL_ORDER

On entry, ORDER  specifies the storage format of the operands as follows:                                                  
  ORDER = HplRowMajor,                                      
  ORDER = HplColumnMajor.                                  

TRANS   (local input)           const enum HPL_TRANS

On entry,  TRANS  specifies the  operation to be performed as follows:  
  TRANS = HplNoTrans y := alpha*A  *x + beta*y,
  TRANS = HplTrans   y := alpha*A^T*x + beta*y.

M       (local input)           const int

On entry,  M  specifies  the number of rows of  the matrix A. M must be at least zero.

N       (local input)           const int

On entry, N  specifies the number of columns of the matrix A. N must be at least zero.

ALPHA   (local input)           const double

On entry, ALPHA specifies the scalar alpha.   When  ALPHA  is supplied as zero then  A and X  need not be set on input.

A       (local input)           const double *

On entry,  A  points  to an array of size equal to or greater than LDA * n.  Before  entry, the leading m by n part  of the array  A  must contain the matrix coefficients.

LDA     (local input)           const int

On entry,  LDA  specifies  the  leading  dimension  of  A  as declared  in  the  calling  (sub) program.  LDA  must  be  at least MAX(1,m).

X       (local input)           const double *

On entry,  X  is an incremented array of dimension  at  least ( 1 + ( n - 1 ) * abs( INCX ) )  that  contains the vector x.

INCX    (local input)           const int

On entry, INCX specifies the increment for the elements of X. INCX must not be zero.

BETA    (local input)           const double

On entry, BETA  specifies the scalar beta.    When  ALPHA  is supplied as zero then  Y  need not be set on input.

Y       (local input/output)    double *

On entry,  Y  is an incremented array of dimension  at  least ( 1 + ( n - 1 ) * abs( INCY ) )  that  contains the vector y. Before entry with BETA non-zero, the incremented array Y must contain the vector  y.  On exit,  Y  is  overwritten  by  the updated vector y.

INCY    (local input)           const int

On entry, INCY specifies the increment for the elements of Y. INCY must not be zero.

Example

#include "hpl.h"
 int main(int argc, char *argv[])
{
  double a[2*2], x[2], y[2];
  a[0] = 1.0; a[1] = 2.0; a[2] = 3.0; a[3] = 3.0;
  x[0] = 2.0; x[1] = 1.0; y[2] = 1.0; y[3] = 2.0;
  HPL_dgemv( HplColumnMajor, HplNoTrans, 2, 2, 2.0,
             a, 2, x, 1, -1.0, y, 1 );
  printf("y=[%f,%f]\n", y[0], y[1]);
  exit(0); return(0);
}

See Also

HPL_dger (3), HPL_dtrsv (3).

Info

October 26, 2012 HPL 2.1 HPL Library Functions