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Diffstat (limited to 'src/fortran/blas/dtrmv.f')
| -rw-r--r-- | src/fortran/blas/dtrmv.f | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/src/fortran/blas/dtrmv.f b/src/fortran/blas/dtrmv.f new file mode 100644 index 0000000..3d5c61b --- /dev/null +++ b/src/fortran/blas/dtrmv.f @@ -0,0 +1,286 @@ + SUBROUTINE DTRMV ( UPLO, TRANS, DIAG, N, A, LDA, X, INCX ) +* .. Scalar Arguments .. + INTEGER INCX, LDA, N + CHARACTER*1 DIAG, TRANS, UPLO +* .. Array Arguments .. + DOUBLE PRECISION A( LDA, * ), X( * ) +* .. +* +* Purpose +* ======= +* +* DTRMV performs one of the matrix-vector operations +* +* x := A*x, or x := A'*x, +* +* where x is an n element vector and A is an n by n unit, or non-unit, +* upper or lower triangular matrix. +* +* Parameters +* ========== +* +* UPLO - CHARACTER*1. +* On entry, UPLO specifies whether the matrix is an upper or +* lower triangular matrix as follows: +* +* UPLO = 'U' or 'u' A is an upper triangular matrix. +* +* UPLO = 'L' or 'l' A is a lower triangular matrix. +* +* Unchanged on exit. +* +* TRANS - CHARACTER*1. +* On entry, TRANS specifies the operation to be performed as +* follows: +* +* TRANS = 'N' or 'n' x := A*x. +* +* TRANS = 'T' or 't' x := A'*x. +* +* TRANS = 'C' or 'c' x := A'*x. +* +* Unchanged on exit. +* +* DIAG - CHARACTER*1. +* On entry, DIAG specifies whether or not A is unit +* triangular as follows: +* +* DIAG = 'U' or 'u' A is assumed to be unit triangular. +* +* DIAG = 'N' or 'n' A is not assumed to be unit +* triangular. +* +* Unchanged on exit. +* +* N - INTEGER. +* On entry, N specifies the order of the matrix A. +* N must be at least 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 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 matrix and the strictly upper triangular part of +* A is not referenced. +* Note that when DIAG = 'U' or 'u', the diagonal elements of +* A are not referenced either, but are assumed to be unity. +* 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. On exit, X is overwritten with the +* tranformed vector x. +* +* INCX - INTEGER. +* On entry, INCX specifies the increment for the elements of +* X. INCX 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 ZERO + PARAMETER ( ZERO = 0.0D+0 ) +* .. Local Scalars .. + DOUBLE PRECISION TEMP + INTEGER I, INFO, IX, J, JX, KX + LOGICAL NOUNIT +* .. 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( .NOT.LSAME( TRANS, 'N' ).AND. + $ .NOT.LSAME( TRANS, 'T' ).AND. + $ .NOT.LSAME( TRANS, 'C' ) )THEN + INFO = 2 + ELSE IF( .NOT.LSAME( DIAG , 'U' ).AND. + $ .NOT.LSAME( DIAG , 'N' ) )THEN + INFO = 3 + ELSE IF( N.LT.0 )THEN + INFO = 4 + ELSE IF( LDA.LT.MAX( 1, N ) )THEN + INFO = 6 + ELSE IF( INCX.EQ.0 )THEN + INFO = 8 + END IF + IF( INFO.NE.0 )THEN + CALL XERBLA( 'DTRMV ', INFO ) + RETURN + END IF +* +* Quick return if possible. +* + IF( N.EQ.0 ) + $ RETURN +* + NOUNIT = LSAME( DIAG, 'N' ) +* +* Set up the start point in X if the increment is not unity. This +* will be ( N - 1 )*INCX too small for descending loops. +* + 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 A. +* + IF( LSAME( TRANS, 'N' ) )THEN +* +* Form x := A*x. +* + IF( LSAME( UPLO, 'U' ) )THEN + IF( INCX.EQ.1 )THEN + DO 20, J = 1, N + IF( X( J ).NE.ZERO )THEN + TEMP = X( J ) + DO 10, I = 1, J - 1 + X( I ) = X( I ) + TEMP*A( I, J ) + 10 CONTINUE + IF( NOUNIT ) + $ X( J ) = X( J )*A( J, J ) + END IF + 20 CONTINUE + ELSE + JX = KX + DO 40, J = 1, N + IF( X( JX ).NE.ZERO )THEN + TEMP = X( JX ) + IX = KX + DO 30, I = 1, J - 1 + X( IX ) = X( IX ) + TEMP*A( I, J ) + IX = IX + INCX + 30 CONTINUE + IF( NOUNIT ) + $ X( JX ) = X( JX )*A( J, J ) + END IF + JX = JX + INCX + 40 CONTINUE + END IF + ELSE + IF( INCX.EQ.1 )THEN + DO 60, J = N, 1, -1 + IF( X( J ).NE.ZERO )THEN + TEMP = X( J ) + DO 50, I = N, J + 1, -1 + X( I ) = X( I ) + TEMP*A( I, J ) + 50 CONTINUE + IF( NOUNIT ) + $ X( J ) = X( J )*A( J, J ) + END IF + 60 CONTINUE + ELSE + KX = KX + ( N - 1 )*INCX + JX = KX + DO 80, J = N, 1, -1 + IF( X( JX ).NE.ZERO )THEN + TEMP = X( JX ) + IX = KX + DO 70, I = N, J + 1, -1 + X( IX ) = X( IX ) + TEMP*A( I, J ) + IX = IX - INCX + 70 CONTINUE + IF( NOUNIT ) + $ X( JX ) = X( JX )*A( J, J ) + END IF + JX = JX - INCX + 80 CONTINUE + END IF + END IF + ELSE +* +* Form x := A'*x. +* + IF( LSAME( UPLO, 'U' ) )THEN + IF( INCX.EQ.1 )THEN + DO 100, J = N, 1, -1 + TEMP = X( J ) + IF( NOUNIT ) + $ TEMP = TEMP*A( J, J ) + DO 90, I = J - 1, 1, -1 + TEMP = TEMP + A( I, J )*X( I ) + 90 CONTINUE + X( J ) = TEMP + 100 CONTINUE + ELSE + JX = KX + ( N - 1 )*INCX + DO 120, J = N, 1, -1 + TEMP = X( JX ) + IX = JX + IF( NOUNIT ) + $ TEMP = TEMP*A( J, J ) + DO 110, I = J - 1, 1, -1 + IX = IX - INCX + TEMP = TEMP + A( I, J )*X( IX ) + 110 CONTINUE + X( JX ) = TEMP + JX = JX - INCX + 120 CONTINUE + END IF + ELSE + IF( INCX.EQ.1 )THEN + DO 140, J = 1, N + TEMP = X( J ) + IF( NOUNIT ) + $ TEMP = TEMP*A( J, J ) + DO 130, I = J + 1, N + TEMP = TEMP + A( I, J )*X( I ) + 130 CONTINUE + X( J ) = TEMP + 140 CONTINUE + ELSE + JX = KX + DO 160, J = 1, N + TEMP = X( JX ) + IX = JX + IF( NOUNIT ) + $ TEMP = TEMP*A( J, J ) + DO 150, I = J + 1, N + IX = IX + INCX + TEMP = TEMP + A( I, J )*X( IX ) + 150 CONTINUE + X( JX ) = TEMP + JX = JX + INCX + 160 CONTINUE + END IF + END IF + END IF +* + RETURN +* +* End of DTRMV . +* + END |