dspmv (l) - Linux Manuals
dspmv: performs the matrix-vector operation y := alpha*A*x + beta*y,
NAME
DSPMV - performs the matrix-vector operation y := alpha*A*x + beta*y,SYNOPSIS
- SUBROUTINE DSPMV(UPLO,N,ALPHA,AP,X,INCX,BETA,Y,INCY)
- DOUBLE PRECISION ALPHA,BETA
- INTEGER INCX,INCY,N
- CHARACTER UPLO
- DOUBLE PRECISION AP(*),X(*),Y(*)
PURPOSE
DSPMV performs the matrix-vector operationwhere alpha and beta are scalars, x and y are n element vectors and A is an n by n symmetric matrix, supplied in packed form.
ARGUMENTS
- UPLO - CHARACTER*1.
-
On entry, UPLO specifies whether the upper or lower
triangular part of the matrix A is supplied in the packed
array AP as follows:
UPLO = aqUaq or aquaq The upper triangular part of A is supplied in AP.
UPLO = aqLaq or aqlaq The lower triangular part of A is supplied in AP.
Unchanged on exit.
- N - INTEGER.
- On entry, N specifies the order 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.
- AP - DOUBLE PRECISION array of DIMENSION at least
- ( ( n*( n + 1 ) )/2 ). Before entry with UPLO = aqUaq or aquaq, the array AP must contain the upper triangular part of the symmetric matrix packed sequentially, column by column, so that AP( 1 ) contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 ) and a( 2, 2 ) respectively, and so on. Before entry with UPLO = aqLaq or aqlaq, the array AP must contain the lower triangular part of the symmetric matrix packed sequentially, column by column, so that AP( 1 ) contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 ) and a( 3, 1 ) respectively, and so on. Unchanged on exit.
- X - DOUBLE PRECISION array of dimension at least
- ( 1 + ( n - 1 )*abs( INCX ) ). Before entry, the incremented array X must contain the n element 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 + ( n - 1 )*abs( INCY ) ). Before entry, the incremented array Y must contain the n element 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.