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Diffstat (limited to '2.3-1/src/fortran/lapack/dlarf.f')
-rw-r--r-- | 2.3-1/src/fortran/lapack/dlarf.f | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/2.3-1/src/fortran/lapack/dlarf.f b/2.3-1/src/fortran/lapack/dlarf.f new file mode 100644 index 00000000..22edc899 --- /dev/null +++ b/2.3-1/src/fortran/lapack/dlarf.f @@ -0,0 +1,115 @@ + SUBROUTINE DLARF( SIDE, M, N, V, INCV, TAU, C, LDC, WORK ) +* +* -- LAPACK auxiliary routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER SIDE + INTEGER INCV, LDC, M, N + DOUBLE PRECISION TAU +* .. +* .. Array Arguments .. + DOUBLE PRECISION C( LDC, * ), V( * ), WORK( * ) +* .. +* +* Purpose +* ======= +* +* DLARF applies a real elementary reflector H to a real m by n matrix +* C, from either the left or the right. H is represented in the form +* +* H = I - tau * v * v' +* +* where tau is a real scalar and v is a real vector. +* +* If tau = 0, then H is taken to be the unit matrix. +* +* Arguments +* ========= +* +* SIDE (input) CHARACTER*1 +* = 'L': form H * C +* = 'R': form C * H +* +* M (input) INTEGER +* The number of rows of the matrix C. +* +* N (input) INTEGER +* The number of columns of the matrix C. +* +* V (input) DOUBLE PRECISION array, dimension +* (1 + (M-1)*abs(INCV)) if SIDE = 'L' +* or (1 + (N-1)*abs(INCV)) if SIDE = 'R' +* The vector v in the representation of H. V is not used if +* TAU = 0. +* +* INCV (input) INTEGER +* The increment between elements of v. INCV <> 0. +* +* TAU (input) DOUBLE PRECISION +* The value tau in the representation of H. +* +* C (input/output) DOUBLE PRECISION array, dimension (LDC,N) +* On entry, the m by n matrix C. +* On exit, C is overwritten by the matrix H * C if SIDE = 'L', +* or C * H if SIDE = 'R'. +* +* LDC (input) INTEGER +* The leading dimension of the array C. LDC >= max(1,M). +* +* WORK (workspace) DOUBLE PRECISION array, dimension +* (N) if SIDE = 'L' +* or (M) if SIDE = 'R' +* +* ===================================================================== +* +* .. Parameters .. + DOUBLE PRECISION ONE, ZERO + PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 ) +* .. +* .. External Subroutines .. + EXTERNAL DGEMV, DGER +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. Executable Statements .. +* + IF( LSAME( SIDE, 'L' ) ) THEN +* +* Form H * C +* + IF( TAU.NE.ZERO ) THEN +* +* w := C' * v +* + CALL DGEMV( 'Transpose', M, N, ONE, C, LDC, V, INCV, ZERO, + $ WORK, 1 ) +* +* C := C - v * w' +* + CALL DGER( M, N, -TAU, V, INCV, WORK, 1, C, LDC ) + END IF + ELSE +* +* Form C * H +* + IF( TAU.NE.ZERO ) THEN +* +* w := C * v +* + CALL DGEMV( 'No transpose', M, N, ONE, C, LDC, V, INCV, + $ ZERO, WORK, 1 ) +* +* C := C - w * v' +* + CALL DGER( M, N, -TAU, WORK, 1, V, INCV, C, LDC ) + END IF + END IF + RETURN +* +* End of DLARF +* + END |