Note: this is a BLAS routine and is not in libslatec.a
*DECK DSYR2
SUBROUTINE DSYR2 (UPLO, N, ALPHA, X, INCX, Y, INCY, A, LDA)
C***BEGIN PROLOGUE DSYR2
C***PURPOSE Perform the symmetric rank 2 operation.
C***LIBRARY SLATEC (BLAS)
C***CATEGORY D1B4
C***TYPE DOUBLE PRECISION (SSYR2-S, DSYR2-D, CSYR2-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 DSYR2 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 n
C by n symmetric matrix.
C
C Parameters
C ==========
C
C UPLO - CHARACTER*1.
C On entry, UPLO specifies whether the upper or lower
C triangular part of the array A is to be referenced as
C follows:
C
C UPLO = 'U' or 'u' Only the upper triangular part of A
C is to be referenced.
C
C UPLO = 'L' or 'l' Only the lower triangular part of A
C is to be referenced.
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 - DOUBLE PRECISION.
C On entry, ALPHA specifies the scalar alpha.
C Unchanged on exit.
C
C X - DOUBLE PRECISION 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 - DOUBLE PRECISION 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 A - DOUBLE PRECISION array of DIMENSION ( LDA, n ).
C Before entry with UPLO = 'U' or 'u', the leading n by n
C upper triangular part of the array A must contain the upper
C triangular part of the symmetric matrix and the strictly
C lower triangular part of A is not referenced. On exit, the
C upper triangular part of the array A is overwritten by the
C upper triangular part of the updated matrix.
C Before entry with UPLO = 'L' or 'l', the leading n by n
C lower triangular part of the array A must contain the lower
C triangular part of the symmetric matrix and the strictly
C upper triangular part of A is not referenced. On exit, the
C lower triangular part of the array A is overwritten by the
C lower triangular part of the updated matrix.
C
C LDA - INTEGER.
C On entry, LDA specifies the first dimension of A as declared
C in the calling (sub) program. LDA must be at least
C max( 1, n ).
C Unchanged on exit.
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 DSYR2