NAME

BLAS/SRC/sgemv.f

SYNOPSIS

Functions/Subroutines

subroutine sgemv (trans, m, n, alpha, a, lda, x, incx, beta, y, incy)
SGEMV

Function/Subroutine Documentation

subroutine sgemv (character trans, integer m, integer n, real alpha, real, dimension(lda,) a, integer lda, real, dimension() x, integer incx, real beta, real, dimension(*) y, integer incy)

SGEMV

Purpose:



 SGEMV  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.

Parameters

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 is INTEGER


           On entry, M specifies the number of rows of the matrix A.


           M must be at least zero.



          N is INTEGER


           On entry, N specifies the number of columns of the matrix A.


           N must be at least zero.

ALPHA



          ALPHA is REAL


           On entry, ALPHA specifies the scalar alpha.



          A is REAL 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 is REAL 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 REAL


           On entry, BETA specifies the scalar beta. When BETA is


           supplied as zero then Y need not be set on input.



          Y is REAL 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.


           If either m or n is zero, then Y not referenced and the function


           performs a quick return.

INCY



          INCY is INTEGER


           On entry, INCY specifies the increment for the elements of


           Y. INCY must not be zero.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

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.

Definition at line 157 of file sgemv.f.

Author