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HPL_dgemv(3) HPL Library Functions HPL_dgemv(3)

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

#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 );

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.

On entry, ORDER specifies the storage format of the operands as follows:
ORDER = HplRowMajor,
ORDER = HplColumnMajor.
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.
On entry, M specifies the number of rows of the matrix A. M must be at least zero.
On entry, N specifies the number of columns of the matrix A. N must be at least zero.
On entry, ALPHA specifies the scalar alpha. When ALPHA is supplied as zero then A and X need not be set on input.
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.
On entry, LDA specifies the leading dimension of A as declared in the calling (sub) program. LDA must be at least MAX(1,m).
On entry, X is an incremented array of dimension at least ( 1 + ( n - 1 ) * abs( INCX ) ) that contains the vector x.
On entry, INCX specifies the increment for the elements of X. INCX must not be zero.
On entry, BETA specifies the scalar beta. When ALPHA is supplied as zero then Y need not be set on input.
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.
On entry, INCY specifies the increment for the elements of Y. INCY must not be zero.

#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);
}

HPL_dger (3), HPL_dtrsv (3).

December 2, 2018 HPL 2.3

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