dsyr2

NAME

dsyr2 - perform the symmetric rank 2 operation A := alpha*x*y' + alpha*y*x' + A

SYNOPSIS 

  SUBROUTINE DSYR2( UPLO, N, ALPHA, X, INCX, Y, INCY, A, LDA)
  CHARACTER * 1 UPLO
  INTEGER N, INCX, INCY, LDA
  DOUBLE PRECISION ALPHA
  DOUBLE PRECISION X(*), Y(*), A(LDA,*)
 
  SUBROUTINE DSYR2_64( UPLO, N, ALPHA, X, INCX, Y, INCY, A, LDA)
  CHARACTER * 1 UPLO
  INTEGER*8 N, INCX, INCY, LDA
  DOUBLE PRECISION ALPHA
  DOUBLE PRECISION X(*), Y(*), A(LDA,*)

F95 INTERFACE 

  SUBROUTINE SYR2( UPLO, [N], ALPHA, X, [INCX], Y, [INCY], A, [LDA])
  CHARACTER(LEN=1) :: UPLO
  INTEGER :: N, INCX, INCY, LDA
  REAL(8) :: ALPHA
  REAL(8), DIMENSION(:) :: X, Y
  REAL(8), DIMENSION(:,:) :: A
 
  SUBROUTINE SYR2_64( UPLO, [N], ALPHA, X, [INCX], Y, [INCY], A, [LDA])
  CHARACTER(LEN=1) :: UPLO
  INTEGER(8) :: N, INCX, INCY, LDA
  REAL(8) :: ALPHA
  REAL(8), DIMENSION(:) :: X, Y
  REAL(8), DIMENSION(:,:) :: A

C INTERFACE

#include <sunperf.h>

void dsyr2(char uplo, int n, double alpha, double *x, int incx, double *y, int incy, double *a, int lda);

void dsyr2_64(char uplo, long n, double alpha, double *x, long incx, double *y, long incy, double *a, long lda);

PURPOSE

dsyr2 performs the symmetric rank 2 operation A := alpha*x*y' + alpha*y*x' + A, where alpha is a scalar, x and y are n element vectors and A is an n by n symmetric matrix.

ARGUMENTS

* UPLO (input)
On entry, UPLO specifies whether the upper or lower triangular part of the array A is to be referenced as follows:

UPLO = 'U' or 'u' Only the upper triangular part of A is to be referenced.

UPLO = 'L' or 'l' Only the lower triangular part of A is to be referenced.

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.

* 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.

* Y (input)
( 1 + ( n - 1 )*abs( INCY ) ). Before entry, the incremented array Y must contain the n element vector y. Unchanged on exit.

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

* A (input/output)
Before entry with UPLO = 'U' or 'u', the leading n by n upper triangular part of the array A must contain the upper triangular part of the symmetric matrix and the strictly lower triangular part of A is not referenced. On exit, the upper triangular part of the array A is overwritten by the upper triangular part of the updated matrix. Before entry with UPLO = 'L' or 'l', the leading n by n lower triangular part of the array A must contain the lower triangular part of the symmetric matrix and the strictly upper triangular part of A is not referenced. On exit, the lower triangular part of the array A is overwritten by the lower triangular part of the updated matrix.

* LDA (input)
On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. LDA >= max( 1, n ). Unchanged on exit.