NAME

dgemv - perform one of the matrix-vector operations y := alpha∗A∗x + beta∗y or y := alpha∗A’∗x + beta∗y

SYNOPSIS

SUBROUTINE DGEMV
( TRANS, M, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY )

void dgemv(char trans, long int m, long int n, double
alpha, double ∗da, long int lda, double ∗dx, long int incx, double dbeta, double ∗dy, long int incy)

DOUBLE PRECISION ALPHA, BETA

INTEGER INCX, INCY, LDA, M, N

CHARACTER∗1 TRANS

DOUBLE PRECISION A( LDA, ∗ ), X( ∗ ), Y( ∗ )

PURPOSE

DGEMV  performs one of the matrix-vector operations y := alpha∗A∗x + beta∗y or y := alpha∗A’∗x + beta∗y where alpha and beta are scalars, x and y are vectors and A is an m by n matrix. 
 

PARAMETERS

TRANS  - CHARACTER∗1. 
On entry, TRANS specifies the operation to be performed as follows:
 
TRANS = ’N’ or ’n’   y := alpha∗A∗x + beta∗y.
 
TRANS = ’T’ or ’t’   y := alpha∗A’∗x + beta∗y.
 
TRANS = ’C’ or ’c’   y := alpha∗A’∗x + beta∗y.
 
Unchanged on exit.

M      - INTEGER. 
On entry, M specifies the number of rows of the matrix A. M must be at least zero. Unchanged on exit.

N      - INTEGER. 
On entry, N specifies the number of columns of the matrix A. N must be at least zero. Unchanged on exit.

ALPHA  - DOUBLE PRECISION. 
On entry, ALPHA specifies the scalar alpha. Unchanged on exit.

A      - DOUBLE PRECISION array of DIMENSION ( LDA, n ). 
Before entry, the leading m by n part of the array A must contain the matrix of coefficients. Unchanged on exit.

LDA    - INTEGER. 
On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. LDA must be at least max( 1, m ). Unchanged on exit.

X      - DOUBLE PRECISION array of DIMENSION at least
( 1 + ( n - 1 )∗abs( INCX ) ) when TRANS = ’N’ or ’n’ and at least ( 1 + ( m - 1 )∗abs( INCX ) ) otherwise. Before entry, the incremented array X must contain the vector x. Unchanged on exit.

INCX   - INTEGER. 
On entry, INCX specifies the increment for the elements of X. INCX must not be zero. Unchanged on exit.

BETA   - DOUBLE PRECISION. 
On entry, BETA specifies the scalar beta. When BETA is supplied as zero then Y need not be set on input. Unchanged on exit.

Y      - DOUBLE PRECISION array of DIMENSION at least
( 1 + ( m - 1 )∗abs( INCY ) ) when TRANS = ’N’ or ’n’ and at least ( 1 + ( n - 1 )∗abs( INCY ) ) otherwise. 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   - INTEGER. 
On entry, INCY specifies the increment for the elements of Y. INCY must not be zero. Unchanged on exit.

Sun, Inc.  —  Last change: 20 Sep 1996