diff options
Diffstat (limited to '2.3-1/src/fortran/lapack/dlarzb.f')
| -rw-r--r-- | 2.3-1/src/fortran/lapack/dlarzb.f | 220 |
1 files changed, 220 insertions, 0 deletions
diff --git a/2.3-1/src/fortran/lapack/dlarzb.f b/2.3-1/src/fortran/lapack/dlarzb.f new file mode 100644 index 00000000..ec59d8d5 --- /dev/null +++ b/2.3-1/src/fortran/lapack/dlarzb.f @@ -0,0 +1,220 @@ + SUBROUTINE DLARZB( SIDE, TRANS, DIRECT, STOREV, M, N, K, L, V, + $ LDV, T, LDT, C, LDC, WORK, LDWORK ) +* +* -- LAPACK routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER DIRECT, SIDE, STOREV, TRANS + INTEGER K, L, LDC, LDT, LDV, LDWORK, M, N +* .. +* .. Array Arguments .. + DOUBLE PRECISION C( LDC, * ), T( LDT, * ), V( LDV, * ), + $ WORK( LDWORK, * ) +* .. +* +* Purpose +* ======= +* +* DLARZB applies a real block reflector H or its transpose H**T to +* a real distributed M-by-N C from the left or the right. +* +* Currently, only STOREV = 'R' and DIRECT = 'B' are supported. +* +* Arguments +* ========= +* +* SIDE (input) CHARACTER*1 +* = 'L': apply H or H' from the Left +* = 'R': apply H or H' from the Right +* +* TRANS (input) CHARACTER*1 +* = 'N': apply H (No transpose) +* = 'C': apply H' (Transpose) +* +* DIRECT (input) CHARACTER*1 +* Indicates how H is formed from a product of elementary +* reflectors +* = 'F': H = H(1) H(2) . . . H(k) (Forward, not supported yet) +* = 'B': H = H(k) . . . H(2) H(1) (Backward) +* +* STOREV (input) CHARACTER*1 +* Indicates how the vectors which define the elementary +* reflectors are stored: +* = 'C': Columnwise (not supported yet) +* = 'R': Rowwise +* +* M (input) INTEGER +* The number of rows of the matrix C. +* +* N (input) INTEGER +* The number of columns of the matrix C. +* +* K (input) INTEGER +* The order of the matrix T (= the number of elementary +* reflectors whose product defines the block reflector). +* +* L (input) INTEGER +* The number of columns of the matrix V containing the +* meaningful part of the Householder reflectors. +* If SIDE = 'L', M >= L >= 0, if SIDE = 'R', N >= L >= 0. +* +* V (input) DOUBLE PRECISION array, dimension (LDV,NV). +* If STOREV = 'C', NV = K; if STOREV = 'R', NV = L. +* +* LDV (input) INTEGER +* The leading dimension of the array V. +* If STOREV = 'C', LDV >= L; if STOREV = 'R', LDV >= K. +* +* T (input) DOUBLE PRECISION array, dimension (LDT,K) +* The triangular K-by-K matrix T in the representation of the +* block reflector. +* +* LDT (input) INTEGER +* The leading dimension of the array T. LDT >= K. +* +* C (input/output) DOUBLE PRECISION array, dimension (LDC,N) +* On entry, the M-by-N matrix C. +* On exit, C is overwritten by H*C or H'*C or C*H or C*H'. +* +* LDC (input) INTEGER +* The leading dimension of the array C. LDC >= max(1,M). +* +* WORK (workspace) DOUBLE PRECISION array, dimension (LDWORK,K) +* +* LDWORK (input) INTEGER +* The leading dimension of the array WORK. +* If SIDE = 'L', LDWORK >= max(1,N); +* if SIDE = 'R', LDWORK >= max(1,M). +* +* Further Details +* =============== +* +* Based on contributions by +* A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA +* +* ===================================================================== +* +* .. Parameters .. + DOUBLE PRECISION ONE + PARAMETER ( ONE = 1.0D+0 ) +* .. +* .. Local Scalars .. + CHARACTER TRANST + INTEGER I, INFO, J +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. External Subroutines .. + EXTERNAL DCOPY, DGEMM, DTRMM, XERBLA +* .. +* .. Executable Statements .. +* +* Quick return if possible +* + IF( M.LE.0 .OR. N.LE.0 ) + $ RETURN +* +* Check for currently supported options +* + INFO = 0 + IF( .NOT.LSAME( DIRECT, 'B' ) ) THEN + INFO = -3 + ELSE IF( .NOT.LSAME( STOREV, 'R' ) ) THEN + INFO = -4 + END IF + IF( INFO.NE.0 ) THEN + CALL XERBLA( 'DLARZB', -INFO ) + RETURN + END IF +* + IF( LSAME( TRANS, 'N' ) ) THEN + TRANST = 'T' + ELSE + TRANST = 'N' + END IF +* + IF( LSAME( SIDE, 'L' ) ) THEN +* +* Form H * C or H' * C +* +* W( 1:n, 1:k ) = C( 1:k, 1:n )' +* + DO 10 J = 1, K + CALL DCOPY( N, C( J, 1 ), LDC, WORK( 1, J ), 1 ) + 10 CONTINUE +* +* W( 1:n, 1:k ) = W( 1:n, 1:k ) + ... +* C( m-l+1:m, 1:n )' * V( 1:k, 1:l )' +* + IF( L.GT.0 ) + $ CALL DGEMM( 'Transpose', 'Transpose', N, K, L, ONE, + $ C( M-L+1, 1 ), LDC, V, LDV, ONE, WORK, LDWORK ) +* +* W( 1:n, 1:k ) = W( 1:n, 1:k ) * T' or W( 1:m, 1:k ) * T +* + CALL DTRMM( 'Right', 'Lower', TRANST, 'Non-unit', N, K, ONE, T, + $ LDT, WORK, LDWORK ) +* +* C( 1:k, 1:n ) = C( 1:k, 1:n ) - W( 1:n, 1:k )' +* + DO 30 J = 1, N + DO 20 I = 1, K + C( I, J ) = C( I, J ) - WORK( J, I ) + 20 CONTINUE + 30 CONTINUE +* +* C( m-l+1:m, 1:n ) = C( m-l+1:m, 1:n ) - ... +* V( 1:k, 1:l )' * W( 1:n, 1:k )' +* + IF( L.GT.0 ) + $ CALL DGEMM( 'Transpose', 'Transpose', L, N, K, -ONE, V, LDV, + $ WORK, LDWORK, ONE, C( M-L+1, 1 ), LDC ) +* + ELSE IF( LSAME( SIDE, 'R' ) ) THEN +* +* Form C * H or C * H' +* +* W( 1:m, 1:k ) = C( 1:m, 1:k ) +* + DO 40 J = 1, K + CALL DCOPY( M, C( 1, J ), 1, WORK( 1, J ), 1 ) + 40 CONTINUE +* +* W( 1:m, 1:k ) = W( 1:m, 1:k ) + ... +* C( 1:m, n-l+1:n ) * V( 1:k, 1:l )' +* + IF( L.GT.0 ) + $ CALL DGEMM( 'No transpose', 'Transpose', M, K, L, ONE, + $ C( 1, N-L+1 ), LDC, V, LDV, ONE, WORK, LDWORK ) +* +* W( 1:m, 1:k ) = W( 1:m, 1:k ) * T or W( 1:m, 1:k ) * T' +* + CALL DTRMM( 'Right', 'Lower', TRANS, 'Non-unit', M, K, ONE, T, + $ LDT, WORK, LDWORK ) +* +* C( 1:m, 1:k ) = C( 1:m, 1:k ) - W( 1:m, 1:k ) +* + DO 60 J = 1, K + DO 50 I = 1, M + C( I, J ) = C( I, J ) - WORK( I, J ) + 50 CONTINUE + 60 CONTINUE +* +* C( 1:m, n-l+1:n ) = C( 1:m, n-l+1:n ) - ... +* W( 1:m, 1:k ) * V( 1:k, 1:l ) +* + IF( L.GT.0 ) + $ CALL DGEMM( 'No transpose', 'No transpose', M, L, K, -ONE, + $ WORK, LDWORK, V, LDV, ONE, C( 1, N-L+1 ), LDC ) +* + END IF +* + RETURN +* +* End of DLARZB +* + END |