dspr2
dspr2 - perform the symmetric rank 2 operation A := alpha*x*y' + alpha*y*x' + A
SUBROUTINE DSPR2( UPLO, N, ALPHA, X, INCX, Y, INCY, A)
CHARACTER * 1 UPLO
INTEGER N, INCX, INCY
DOUBLE PRECISION ALPHA
DOUBLE PRECISION X(*), Y(*), A(*)
SUBROUTINE DSPR2_64( UPLO, N, ALPHA, X, INCX, Y, INCY, A)
CHARACTER * 1 UPLO
INTEGER*8 N, INCX, INCY
DOUBLE PRECISION ALPHA
DOUBLE PRECISION X(*), Y(*), A(*)
SUBROUTINE SPR2( UPLO, [N], ALPHA, X, [INCX], Y, [INCY], A)
CHARACTER(LEN=1) :: UPLO
INTEGER :: N, INCX, INCY
REAL(8) :: ALPHA
REAL(8), DIMENSION(:) :: X, Y, A
SUBROUTINE SPR2_64( UPLO, [N], ALPHA, X, [INCX], Y, [INCY], A)
CHARACTER(LEN=1) :: UPLO
INTEGER(8) :: N, INCX, INCY
REAL(8) :: ALPHA
REAL(8), DIMENSION(:) :: X, Y, A
#include <sunperf.h>
void dspr2(char uplo, int n, double alpha, double *x, int incx, double *y, int incy, double *a);
void dspr2_64(char uplo, long n, double alpha, double *x, long incx, double *y, long incy, double *a);
dspr2 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, supplied in packed form.
-
* 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.
-
* 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)
-
( ( 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. On exit, the array
A is overwritten by the upper triangular part of the
updated matrix.
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. On exit, the array
A is overwritten by the lower triangular part of the
updated matrix.