• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

sspmv - perform the matrix-vector operation y := alpha*A*x + beta*y

SYNOPSIS

  SUBROUTINE SSPMV( UPLO, N, ALPHA, A, X, INCX, BETA, Y, INCY)
  CHARACTER * 1 UPLO
  INTEGER N, INCX, INCY
  REAL ALPHA, BETA
  REAL A(*), X(*), Y(*)

  SUBROUTINE SSPMV_64( UPLO, N, ALPHA, A, X, INCX, BETA, Y, INCY)
  CHARACTER * 1 UPLO
  INTEGER*8 N, INCX, INCY
  REAL ALPHA, BETA
  REAL A(*), X(*), Y(*)

F95 INTERFACE

  SUBROUTINE SPMV( UPLO, N, ALPHA, A, X, [INCX], BETA, Y, [INCY])
  CHARACTER(LEN=1) :: UPLO
  INTEGER :: N, INCX, INCY
  REAL :: ALPHA, BETA
  REAL, DIMENSION(:) :: A, X, Y

  SUBROUTINE SPMV_64( UPLO, N, ALPHA, A, X, [INCX], BETA, Y, [INCY])
  CHARACTER(LEN=1) :: UPLO
  INTEGER(8) :: N, INCX, INCY
  REAL :: ALPHA, BETA
  REAL, DIMENSION(:) :: A, X, Y

C INTERFACE

#include <sunperf.h>

void sspmv(char uplo, int n, float alpha, float *a, float *x, int incx, float beta, float *y, int incy);

void sspmv_64(char uplo, long n, float alpha, float *a, float *x, long incx, float beta, float *y, long incy);

PURPOSE

sspmv performs the matrix-vector operation y := alpha*A*x + beta*y, where 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 (input)
  On entry, UPLO specifies whether the upper or lower triangular part of the matrix A is supplied in the packed array A as follows:

  UPLO = 'U' or 'u' The upper triangular part of A is supplied in A.

  UPLO = 'L' or 'l' The lower triangular part of A is supplied in A.

  Unchanged on exit.

• N (input)
  On entry, N specifies the order of the matrix A. N > = 0. Unchanged on exit.

• ALPHA (input)
  On entry, ALPHA specifies the scalar alpha. Unchanged on exit.

• A (input)
  ( ( n*( n + 1 ) )/2 ). Before entry with UPLO = 'U' or 'u', the array A must contain the upper triangular part of the symmetric matrix packed sequentially, column by column, so that A( 1 ) contains a( 1, 1 ), A( 2 ) and A( 3 ) contain a( 1, 2 ) and a( 2, 2 ) respectively, and so on. Before entry with UPLO = 'L' or 'l', the array A must contain the lower triangular part of the symmetric matrix packed sequentially, column by column, so that A( 1 ) contains a( 1, 1 ), A( 2 ) and A( 3 ) contain a( 2, 1 ) and a( 3, 1 ) respectively, and so on. Unchanged on exit.

• X (input)
  ( 1 + ( n - 1 )*abs( INCX ) ). Before entry, the incremented array X must contain the n element vector x. Unchanged on exit.

• INCX (input)
  On entry, INCX specifies the increment for the elements of X. INCX < > 0. Unchanged on exit.

• BETA (input)
  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 (input/output)
  ( 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 (input)
  On entry, INCY specifies the increment for the elements of Y. INCY < > 0. Unchanged on exit.