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Diffstat (limited to '2.3-1/src/fortran/blas/dsymv.f')
| -rw-r--r-- | 2.3-1/src/fortran/blas/dsymv.f | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/2.3-1/src/fortran/blas/dsymv.f b/2.3-1/src/fortran/blas/dsymv.f new file mode 100644 index 00000000..7592d156 --- /dev/null +++ b/2.3-1/src/fortran/blas/dsymv.f @@ -0,0 +1,262 @@ + SUBROUTINE DSYMV ( UPLO, N, ALPHA, A, LDA, X, INCX, + $ BETA, Y, INCY ) +* .. Scalar Arguments .. + DOUBLE PRECISION ALPHA, BETA + INTEGER INCX, INCY, LDA, N + CHARACTER*1 UPLO +* .. Array Arguments .. + DOUBLE PRECISION A( LDA, * ), X( * ), Y( * ) +* .. +* +* Purpose +* ======= +* +* DSYMV performs the matrix-vector operation +* +* y := alpha*A*x + beta*y, +* +* where alpha and beta are scalars, x and y are n element vectors 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. +* +* 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. +* 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. +* Unchanged on exit. +* +* 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. +* +* 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. +* +* BETA - DOUBLE PRECISION. +* On entry, BETA specifies the scalar beta. When BETA is +* supplied as zero then Y need not be set on input. +* Unchanged on exit. +* +* Y - DOUBLE PRECISION array of dimension at least +* ( 1 + ( n - 1 )*abs( INCY ) ). +* Before entry, the incremented array Y must contain the n +* element vector y. On exit, Y is overwritten by the updated +* vector y. +* +* INCY - INTEGER. +* On entry, INCY specifies the increment for the elements of +* Y. INCY must not be zero. +* 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 ONE , ZERO + PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 ) +* .. Local Scalars .. + DOUBLE PRECISION TEMP1, TEMP2 + INTEGER I, INFO, IX, IY, J, JX, JY, KX, KY +* .. 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( LDA.LT.MAX( 1, N ) )THEN + INFO = 5 + ELSE IF( INCX.EQ.0 )THEN + INFO = 7 + ELSE IF( INCY.EQ.0 )THEN + INFO = 10 + END IF + IF( INFO.NE.0 )THEN + CALL XERBLA( 'DSYMV ', INFO ) + RETURN + END IF +* +* Quick return if possible. +* + IF( ( N.EQ.0 ).OR.( ( ALPHA.EQ.ZERO ).AND.( BETA.EQ.ONE ) ) ) + $ RETURN +* +* Set up the start points in X and Y. +* + IF( INCX.GT.0 )THEN + KX = 1 + ELSE + KX = 1 - ( N - 1 )*INCX + END IF + IF( INCY.GT.0 )THEN + KY = 1 + ELSE + KY = 1 - ( N - 1 )*INCY + END IF +* +* Start the operations. In this version the elements of A are +* accessed sequentially with one pass through the triangular part +* of A. +* +* First form y := beta*y. +* + IF( BETA.NE.ONE )THEN + IF( INCY.EQ.1 )THEN + IF( BETA.EQ.ZERO )THEN + DO 10, I = 1, N + Y( I ) = ZERO + 10 CONTINUE + ELSE + DO 20, I = 1, N + Y( I ) = BETA*Y( I ) + 20 CONTINUE + END IF + ELSE + IY = KY + IF( BETA.EQ.ZERO )THEN + DO 30, I = 1, N + Y( IY ) = ZERO + IY = IY + INCY + 30 CONTINUE + ELSE + DO 40, I = 1, N + Y( IY ) = BETA*Y( IY ) + IY = IY + INCY + 40 CONTINUE + END IF + END IF + END IF + IF( ALPHA.EQ.ZERO ) + $ RETURN + IF( LSAME( UPLO, 'U' ) )THEN +* +* Form y when A is stored in upper triangle. +* + IF( ( INCX.EQ.1 ).AND.( INCY.EQ.1 ) )THEN + DO 60, J = 1, N + TEMP1 = ALPHA*X( J ) + TEMP2 = ZERO + DO 50, I = 1, J - 1 + Y( I ) = Y( I ) + TEMP1*A( I, J ) + TEMP2 = TEMP2 + A( I, J )*X( I ) + 50 CONTINUE + Y( J ) = Y( J ) + TEMP1*A( J, J ) + ALPHA*TEMP2 + 60 CONTINUE + ELSE + JX = KX + JY = KY + DO 80, J = 1, N + TEMP1 = ALPHA*X( JX ) + TEMP2 = ZERO + IX = KX + IY = KY + DO 70, I = 1, J - 1 + Y( IY ) = Y( IY ) + TEMP1*A( I, J ) + TEMP2 = TEMP2 + A( I, J )*X( IX ) + IX = IX + INCX + IY = IY + INCY + 70 CONTINUE + Y( JY ) = Y( JY ) + TEMP1*A( J, J ) + ALPHA*TEMP2 + JX = JX + INCX + JY = JY + INCY + 80 CONTINUE + END IF + ELSE +* +* Form y when A is stored in lower triangle. +* + IF( ( INCX.EQ.1 ).AND.( INCY.EQ.1 ) )THEN + DO 100, J = 1, N + TEMP1 = ALPHA*X( J ) + TEMP2 = ZERO + Y( J ) = Y( J ) + TEMP1*A( J, J ) + DO 90, I = J + 1, N + Y( I ) = Y( I ) + TEMP1*A( I, J ) + TEMP2 = TEMP2 + A( I, J )*X( I ) + 90 CONTINUE + Y( J ) = Y( J ) + ALPHA*TEMP2 + 100 CONTINUE + ELSE + JX = KX + JY = KY + DO 120, J = 1, N + TEMP1 = ALPHA*X( JX ) + TEMP2 = ZERO + Y( JY ) = Y( JY ) + TEMP1*A( J, J ) + IX = JX + IY = JY + DO 110, I = J + 1, N + IX = IX + INCX + IY = IY + INCY + Y( IY ) = Y( IY ) + TEMP1*A( I, J ) + TEMP2 = TEMP2 + A( I, J )*X( IX ) + 110 CONTINUE + Y( JY ) = Y( JY ) + ALPHA*TEMP2 + JX = JX + INCX + JY = JY + INCY + 120 CONTINUE + END IF + END IF +* + RETURN +* +* End of DSYMV . +* + END |