SUBROUTINE DSYR ( UPLO, N, ALPHA, X, INCX, A, LDA ) **************************************************************************** * * * DATA PARALLEL BLAS based on MPL * * * * Version 1.0 1/9-92 , * * For MasPar MP-1 computers * * * * para//ab, University of Bergen, NORWAY * * * * These programs must be called using F90 style array syntax. * * Note that the F77 style calling sequence has been retained * * in this version for compatibility reasons, be aware that * * parameters related to the array dimensions and shape therefore may * * be redundant and without any influence. * * The calling sequence may be changed in a future version. * * Please report any BUGs, ideas for improvement or other * * comments to * * adm@parallab.uib.no * * * * Future versions may then reflect your suggestions. * * The most current version of this software is available * * from netlib@nac.no , send the message `send index from maspar' * * * * REVISIONS: * * * **************************************************************************** implicit none * .. Scalar Arguments .. double precision ALPHA INTEGER INCX, LDA, N CHARACTER*1 UPLO * .. Array Arguments .. double precision, array(:,:) :: a double precision, array(:) :: x intent(in) :: x intent(inout) :: a * .. * * Purpose * ======= * * DSYR performs the symmetric rank 1 operation * * A := alpha*x*x' + A, * * where alpha is a double precision scalar, x is an n element vector and A is an * n by n symmetric matrix. * * Parameters * ========== * * UPLO - CHARACTER*1. * 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 - INTEGER. * On entry, N specifies the order of the matrix A. * N must be at least zero. * Unchanged on exit. * * ALPHA - double precision. * On entry, ALPHA specifies the scalar alpha. * Unchanged on exit. * * X - double precision array of dimension at least * ( 1 + ( n - 1 )*abs( INCX ) ). * Before entry, the incremented array X must contain the n * element vector x. * Unchanged on exit. * * INCX - INTEGER. * On entry, INCX specifies the increment for the elements of * X. INCX must not be zero. * Unchanged on exit. * * A - double precision array of DIMENSION ( LDA, n ). * 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 - INTEGER. * On entry, LDA specifies the first dimension of A as declared * in the calling (sub) program. LDA must be at least * max( 1, n ). * Unchanged on exit. * * * Level 2 Blas routine. * * -- Written on 22-October-1986. * Jack Dongarra, Argonne National Lab. * Jeremy Du Croz, Nag Central Office. * Sven Hammarling, Nag Central Office. * Richard Hanson, Sandia National Labs. * * * .. Parameters .. double precision ZERO PARAMETER ( ZERO = 0.0D+0 ) * .. Local Scalars .. double precision TEMP INTEGER I, INFO, IX, J, KX * .. External Functions .. LOGICAL LSAME EXTERNAL LSAME * .. External Subroutines .. EXTERNAL XERBLA * .. Intrinsic Functions .. INTRINSIC MAX * .. * .. Executable Statements .. * * Test the input parameters. * INFO = 0 IF ( .NOT.LSAME( UPLO, 'U' ).AND. $ .NOT.LSAME( UPLO, 'L' ) )THEN INFO = 1 ELSE IF( N.LT.0 )THEN INFO = 2 ELSE IF( INCX.EQ.0 )THEN INFO = 5 ELSE IF( LDA.LT.max( 1, N ) )THEN INFO = 7 END IF IF( INFO.NE.0 )THEN CALL XERBLA( 'DSYR ', INFO ) RETURN END IF * * Quick return if possible. * IF( ( N.EQ.0 ).OR.( ALPHA.EQ.ZERO ) ) RETURN c IF( INCX.LE.0 )THEN KX = 1 - ( N - 1 )*INCX ELSE KX = 1 END IF * IF( LSAME(UPLO,'U') )THEN clater forall (i=1:n, j=1:n, i .le. j) a(i,j) = a(i,j) clater & alpha * x(kx+(j-1)*incx) * x(kx+(i-1)*incx) do j = 1 , n i = kx+(j-1)*incx a(1:j,j) = a(1:j,j) + alpha * x(i) * x(kx:i:incx) enddo ELSE clater forall (i=1:n, j=1:n, i .ge. j) a(i,j) = a(i,j) clater & alpha * x(kx+(i-1)*incx) * x(kx+(j-1)*incx) do i = 1 , n j = kx+(i-1)*incx a(i,1:i) = a(i,1:i) + alpha * x(j) * x(kx:j:incx) enddo END IF * RETURN * * End of DSYR . * END