sspmv (l)  Linux Manuals
sspmv: performs the matrixvector operation y := alpha*A*x + beta*y,
NAME
SSPMV  performs the matrixvector operation y := alpha*A*x + beta*y,SYNOPSIS
 SUBROUTINE SSPMV(UPLO,N,ALPHA,AP,X,INCX,BETA,Y,INCY)
 REAL ALPHA,BETA
 INTEGER INCX,INCY,N
 CHARACTER UPLO
 REAL AP(*),X(*),Y(*)
PURPOSE
SSPMV performs the matrixvector 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  REAL .
 On entry, ALPHA specifies the scalar alpha. Unchanged on exit.
 AP  REAL 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  REAL 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  REAL .
 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  REAL 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 22October1986.
Jack Dongarra, Argonne National Lab.
Jeremy Du Croz, Nag Central Office.
Sven Hammarling, Nag Central Office.
Richard Hanson, Sandia National Labs.