dgemv (l) - Linux Manuals

dgemv: performs one of the matrix-vector operations y := alpha*A*x + beta*y, or y := alpha*Aaq*x + beta*y,

NAME

DGEMV - performs one of the matrix-vector operations y := alpha*A*x + beta*y, or y := alpha*Aaq*x + beta*y,

SYNOPSIS

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

    
DOUBLE PRECISION ALPHA,BETA

    
INTEGER INCX,INCY,LDA,M,N

    
CHARACTER TRANS

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

PURPOSE

DGEMV performs one of the matrix-vector operations

where alpha and beta are scalars, x and y are vectors and A is an m by n matrix.

ARGUMENTS

TRANS - CHARACTER*1.
On entry, TRANS specifies the operation to be performed as follows:

TRANS = aqNaq or aqnaq y := alpha*A*x + beta*y.

TRANS = aqTaq or aqtaq y := alpha*Aaq*x + beta*y.

TRANS = aqCaq or aqcaq y := alpha*Aaq*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 = aqNaq or aqnaq 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 = aqNaq or aqnaq 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.

FURTHER DETAILS

Level 2 Blas routine.

-- Written on 22-October-1986.

Jack Dongarra, Argonne National Lab.

Jeremy Du Croz, Nag Central Office.

Sven Hammarling, Nag Central Office.

Richard Hanson, Sandia National Labs.

Pages related to dgemv

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