Note: this is a BLAS routine and is not in libslatec.a
*DECK SSPR2
SUBROUTINE SSPR2 (UPLO, N, ALPHA, X, INCX, Y, INCY, AP)
C***BEGIN PROLOGUE SSPR2
C***PURPOSE Perform the symmetric rank 2 operation.
C***LIBRARY SLATEC (BLAS)
C***CATEGORY D1B4
C***TYPE SINGLE PRECISION (SSPR2-S, DSPR2-D, CSPR2-C)
C***KEYWORDS LEVEL 2 BLAS, LINEAR ALGEBRA
C***AUTHOR Dongarra, J. J., (ANL)
C Du Croz, J., (NAG)
C Hammarling, S., (NAG)
C Hanson, R. J., (SNLA)
C***DESCRIPTION
C
C SSPR2 performs the symmetric rank 2 operation
C
C A := alpha*x*y' + alpha*y*x' + A,
C
C where alpha is a scalar, x and y are n element vectors and A is an
C n by n symmetric matrix, supplied in packed form.
C
C Parameters
C ==========
C
C UPLO - CHARACTER*1.
C On entry, UPLO specifies whether the upper or lower
C triangular part of the matrix A is supplied in the packed
C array AP as follows:
C
C UPLO = 'U' or 'u' The upper triangular part of A is
C supplied in AP.
C
C UPLO = 'L' or 'l' The lower triangular part of A is
C supplied in AP.
C
C Unchanged on exit.
C
C N - INTEGER.
C On entry, N specifies the order of the matrix A.
C N must be at least zero.
C Unchanged on exit.
C
C ALPHA - REAL .
C On entry, ALPHA specifies the scalar alpha.
C Unchanged on exit.
C
C X - REAL array of dimension at least
C ( 1 + ( n - 1)*abs( INCX)).
C Before entry, the incremented array X must contain the n
C element vector x.
C Unchanged on exit.
C
C INCX - INTEGER.
C On entry, INCX specifies the increment for the elements of
C X. INCX must not be zero.
C Unchanged on exit.
C
C Y - REAL array of dimension at least
C ( 1 + ( n - 1 )*abs( INCY ) ).
C Before entry, the incremented array Y must contain the n
C element vector y.
C Unchanged on exit.
C
C INCY - INTEGER.
C On entry, INCY specifies the increment for the elements of
C Y. INCY must not be zero.
C Unchanged on exit.
C
C AP - REAL array of DIMENSION at least
C ( ( n*( n + 1 ) )/2 ).
C Before entry with UPLO = 'U' or 'u', the array AP must
C contain the upper triangular part of the symmetric matrix
C packed sequentially, column by column, so that AP( 1 )
C contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 )
C and a( 2, 2 ) respectively, and so on. On exit, the array
C AP is overwritten by the upper triangular part of the
C updated matrix.
C Before entry with UPLO = 'L' or 'l', the array AP must
C contain the lower triangular part of the symmetric matrix
C packed sequentially, column by column, so that AP( 1 )
C contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 )
C and a( 3, 1 ) respectively, and so on. On exit, the array
C AP is overwritten by the lower triangular part of the
C updated matrix.
C
C***REFERENCES Dongarra, J. J., Du Croz, J., Hammarling, S., and
C Hanson, R. J. An extended set of Fortran basic linear
C algebra subprograms. ACM TOMS, Vol. 14, No. 1,
C pp. 1-17, March 1988.
C***ROUTINES CALLED LSAME, XERBLA
C***REVISION HISTORY (YYMMDD)
C 861022 DATE WRITTEN
C 910605 Modified to meet SLATEC prologue standards. Only comment
C lines were modified. (BKS)
C***END PROLOGUE SSPR2