C Library Functions - dgemv (3)
NAME
dgemv(3f) - [BLAS:DOUBLE_BLAS_LEVEL2]
CONTENTS
Synopsis
Definition
Options
Y
Authors
Further Details
See Also
SYNOPSIS
subroutine dgemv(trans,m,n,alpha,a,lda,x,incx,beta,y,incy)
.. Scalar Arguments .. double precision,intent(in) :: alpha,beta integer,intent(in) :: incx,incy,lda,m,n character,intent(in) :: trans .. .. Array Arguments .. double precision,intent(in) :: a(lda,*),x(*) double precision,intent(inout) :: y(*) ..
DEFINITION
DGEMV performs one of the matrix-vector operations
y := alpha*A*x + beta*y, or y := alpha*A**T*x + beta*y,where alpha and beta are scalars, x and y are vectors and A is an m by n matrix.
OPTIONS
TRANS
TRANS is 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**T*x + beta*y.
TRANS = ’C’ or ’c’ y := alpha*A**T*x + beta*y.
M
M is INTEGER On entry, M specifies the number of rows of the matrix A. M must be at least zero.
N
N is INTEGER On entry, N specifies the number of columns of the matrix A. N must be at least zero.
ALPHA
ALPHA is DOUBLE PRECISION. On entry, ALPHA specifies the scalar alpha.
A
A is DOUBLE PRECISION array, dimension ( LDA, N ) Before entry, the leading m by n part of the array A must contain the matrix of coefficients.
LDA
LDA is 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 ).
X
X is DOUBLE PRECISION array, 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.
INCX
INCX is INTEGER On entry, INCX specifies the increment for the elements of X. INCX must not be zero.
BETA
BETA is DOUBLE PRECISION. On entry, BETA specifies the scalar beta. When BETA is supplied as zero then Y need not be set on input.
Y
Y is DOUBLE PRECISION array, 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
INCY is INTEGER On entry, INCY specifies the increment for the elements of Y. INCY must not be zero.
AUTHORS
o Univ. of Tennessee o Univ. of California Berkeley o Univ. of Colorado Denver o NAG Ltd. date:December 2016
FURTHER DETAILS
Level 2 Blas routine. The vector and matrix arguments are not referenced when N = 0, or M = 0
-- 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.
SEE ALSO
Online html documentation available at http://www.netlib.org/lapack/explore-html/
| Nemo Release 3.1 | dgemv (3) | July 22, 2023 |
