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Diffstat (limited to '2.3-1/src/fortran/blas/dsyr.f')
| -rw-r--r-- | 2.3-1/src/fortran/blas/dsyr.f | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/2.3-1/src/fortran/blas/dsyr.f b/2.3-1/src/fortran/blas/dsyr.f new file mode 100644 index 00000000..87377196 --- /dev/null +++ b/2.3-1/src/fortran/blas/dsyr.f @@ -0,0 +1,197 @@ + SUBROUTINE DSYR ( UPLO, N, ALPHA, X, INCX, A, LDA ) +* .. Scalar Arguments .. + DOUBLE PRECISION ALPHA + INTEGER INCX, LDA, N + CHARACTER*1 UPLO +* .. Array Arguments .. + DOUBLE PRECISION A( LDA, * ), X( * ) +* .. +* +* Purpose +* ======= +* +* DSYR performs the symmetric rank 1 operation +* +* A := alpha*x*x' + A, +* +* where alpha is a real 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, JX, 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 +* +* Set the start point in X if the increment is not unity. +* + IF( INCX.LE.0 )THEN + KX = 1 - ( N - 1 )*INCX + ELSE IF( INCX.NE.1 )THEN + KX = 1 + END IF +* +* Start the operations. In this version the elements of A are +* accessed sequentially with one pass through the triangular part +* of A. +* + IF( LSAME( UPLO, 'U' ) )THEN +* +* Form A when A is stored in upper triangle. +* + IF( INCX.EQ.1 )THEN + DO 20, J = 1, N + IF( X( J ).NE.ZERO )THEN + TEMP = ALPHA*X( J ) + DO 10, I = 1, J + A( I, J ) = A( I, J ) + X( I )*TEMP + 10 CONTINUE + END IF + 20 CONTINUE + ELSE + JX = KX + DO 40, J = 1, N + IF( X( JX ).NE.ZERO )THEN + TEMP = ALPHA*X( JX ) + IX = KX + DO 30, I = 1, J + A( I, J ) = A( I, J ) + X( IX )*TEMP + IX = IX + INCX + 30 CONTINUE + END IF + JX = JX + INCX + 40 CONTINUE + END IF + ELSE +* +* Form A when A is stored in lower triangle. +* + IF( INCX.EQ.1 )THEN + DO 60, J = 1, N + IF( X( J ).NE.ZERO )THEN + TEMP = ALPHA*X( J ) + DO 50, I = J, N + A( I, J ) = A( I, J ) + X( I )*TEMP + 50 CONTINUE + END IF + 60 CONTINUE + ELSE + JX = KX + DO 80, J = 1, N + IF( X( JX ).NE.ZERO )THEN + TEMP = ALPHA*X( JX ) + IX = JX + DO 70, I = J, N + A( I, J ) = A( I, J ) + X( IX )*TEMP + IX = IX + INCX + 70 CONTINUE + END IF + JX = JX + INCX + 80 CONTINUE + END IF + END IF +* + RETURN +* +* End of DSYR . +* + END |