SUBROUTINE DSPR2 (UPLO, N, ALPHA, X, INCX, Y, INCY, AP) C***BEGIN PROLOGUE DSPR2 C***PURPOSE Perform the symmetric rank 2 operation. C***LIBRARY SLATEC (BLAS) C***CATEGORY D1B4 C***TYPE DOUBLE 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 DSPR2 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 - 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 AP - DOUBLE PRECISION 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 DSPR2