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Diffstat (limited to '2.3-1/src/fortran/lapack/zlarft.f')
| -rw-r--r-- | 2.3-1/src/fortran/lapack/zlarft.f | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/2.3-1/src/fortran/lapack/zlarft.f b/2.3-1/src/fortran/lapack/zlarft.f new file mode 100644 index 00000000..412265e3 --- /dev/null +++ b/2.3-1/src/fortran/lapack/zlarft.f @@ -0,0 +1,224 @@ + SUBROUTINE ZLARFT( DIRECT, STOREV, N, K, V, LDV, TAU, T, LDT ) +* +* -- LAPACK auxiliary routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER DIRECT, STOREV + INTEGER K, LDT, LDV, N +* .. +* .. Array Arguments .. + COMPLEX*16 T( LDT, * ), TAU( * ), V( LDV, * ) +* .. +* +* Purpose +* ======= +* +* ZLARFT forms the triangular factor T of a complex block reflector H +* of order n, which is defined as a product of k elementary reflectors. +* +* If DIRECT = 'F', H = H(1) H(2) . . . H(k) and T is upper triangular; +* +* If DIRECT = 'B', H = H(k) . . . H(2) H(1) and T is lower triangular. +* +* If STOREV = 'C', the vector which defines the elementary reflector +* H(i) is stored in the i-th column of the array V, and +* +* H = I - V * T * V' +* +* If STOREV = 'R', the vector which defines the elementary reflector +* H(i) is stored in the i-th row of the array V, and +* +* H = I - V' * T * V +* +* Arguments +* ========= +* +* DIRECT (input) CHARACTER*1 +* Specifies the order in which the elementary reflectors are +* multiplied to form the block reflector: +* = 'F': H = H(1) H(2) . . . H(k) (Forward) +* = 'B': H = H(k) . . . H(2) H(1) (Backward) +* +* STOREV (input) CHARACTER*1 +* Specifies how the vectors which define the elementary +* reflectors are stored (see also Further Details): +* = 'C': columnwise +* = 'R': rowwise +* +* N (input) INTEGER +* The order of the block reflector H. N >= 0. +* +* K (input) INTEGER +* The order of the triangular factor T (= the number of +* elementary reflectors). K >= 1. +* +* V (input/output) COMPLEX*16 array, dimension +* (LDV,K) if STOREV = 'C' +* (LDV,N) if STOREV = 'R' +* The matrix V. See further details. +* +* LDV (input) INTEGER +* The leading dimension of the array V. +* If STOREV = 'C', LDV >= max(1,N); if STOREV = 'R', LDV >= K. +* +* TAU (input) COMPLEX*16 array, dimension (K) +* TAU(i) must contain the scalar factor of the elementary +* reflector H(i). +* +* T (output) COMPLEX*16 array, dimension (LDT,K) +* The k by k triangular factor T of the block reflector. +* If DIRECT = 'F', T is upper triangular; if DIRECT = 'B', T is +* lower triangular. The rest of the array is not used. +* +* LDT (input) INTEGER +* The leading dimension of the array T. LDT >= K. +* +* Further Details +* =============== +* +* The shape of the matrix V and the storage of the vectors which define +* the H(i) is best illustrated by the following example with n = 5 and +* k = 3. The elements equal to 1 are not stored; the corresponding +* array elements are modified but restored on exit. The rest of the +* array is not used. +* +* DIRECT = 'F' and STOREV = 'C': DIRECT = 'F' and STOREV = 'R': +* +* V = ( 1 ) V = ( 1 v1 v1 v1 v1 ) +* ( v1 1 ) ( 1 v2 v2 v2 ) +* ( v1 v2 1 ) ( 1 v3 v3 ) +* ( v1 v2 v3 ) +* ( v1 v2 v3 ) +* +* DIRECT = 'B' and STOREV = 'C': DIRECT = 'B' and STOREV = 'R': +* +* V = ( v1 v2 v3 ) V = ( v1 v1 1 ) +* ( v1 v2 v3 ) ( v2 v2 v2 1 ) +* ( 1 v2 v3 ) ( v3 v3 v3 v3 1 ) +* ( 1 v3 ) +* ( 1 ) +* +* ===================================================================== +* +* .. Parameters .. + COMPLEX*16 ONE, ZERO + PARAMETER ( ONE = ( 1.0D+0, 0.0D+0 ), + $ ZERO = ( 0.0D+0, 0.0D+0 ) ) +* .. +* .. Local Scalars .. + INTEGER I, J + COMPLEX*16 VII +* .. +* .. External Subroutines .. + EXTERNAL ZGEMV, ZLACGV, ZTRMV +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. Executable Statements .. +* +* Quick return if possible +* + IF( N.EQ.0 ) + $ RETURN +* + IF( LSAME( DIRECT, 'F' ) ) THEN + DO 20 I = 1, K + IF( TAU( I ).EQ.ZERO ) THEN +* +* H(i) = I +* + DO 10 J = 1, I + T( J, I ) = ZERO + 10 CONTINUE + ELSE +* +* general case +* + VII = V( I, I ) + V( I, I ) = ONE + IF( LSAME( STOREV, 'C' ) ) THEN +* +* T(1:i-1,i) := - tau(i) * V(i:n,1:i-1)' * V(i:n,i) +* + CALL ZGEMV( 'Conjugate transpose', N-I+1, I-1, + $ -TAU( I ), V( I, 1 ), LDV, V( I, I ), 1, + $ ZERO, T( 1, I ), 1 ) + ELSE +* +* T(1:i-1,i) := - tau(i) * V(1:i-1,i:n) * V(i,i:n)' +* + IF( I.LT.N ) + $ CALL ZLACGV( N-I, V( I, I+1 ), LDV ) + CALL ZGEMV( 'No transpose', I-1, N-I+1, -TAU( I ), + $ V( 1, I ), LDV, V( I, I ), LDV, ZERO, + $ T( 1, I ), 1 ) + IF( I.LT.N ) + $ CALL ZLACGV( N-I, V( I, I+1 ), LDV ) + END IF + V( I, I ) = VII +* +* T(1:i-1,i) := T(1:i-1,1:i-1) * T(1:i-1,i) +* + CALL ZTRMV( 'Upper', 'No transpose', 'Non-unit', I-1, T, + $ LDT, T( 1, I ), 1 ) + T( I, I ) = TAU( I ) + END IF + 20 CONTINUE + ELSE + DO 40 I = K, 1, -1 + IF( TAU( I ).EQ.ZERO ) THEN +* +* H(i) = I +* + DO 30 J = I, K + T( J, I ) = ZERO + 30 CONTINUE + ELSE +* +* general case +* + IF( I.LT.K ) THEN + IF( LSAME( STOREV, 'C' ) ) THEN + VII = V( N-K+I, I ) + V( N-K+I, I ) = ONE +* +* T(i+1:k,i) := +* - tau(i) * V(1:n-k+i,i+1:k)' * V(1:n-k+i,i) +* + CALL ZGEMV( 'Conjugate transpose', N-K+I, K-I, + $ -TAU( I ), V( 1, I+1 ), LDV, V( 1, I ), + $ 1, ZERO, T( I+1, I ), 1 ) + V( N-K+I, I ) = VII + ELSE + VII = V( I, N-K+I ) + V( I, N-K+I ) = ONE +* +* T(i+1:k,i) := +* - tau(i) * V(i+1:k,1:n-k+i) * V(i,1:n-k+i)' +* + CALL ZLACGV( N-K+I-1, V( I, 1 ), LDV ) + CALL ZGEMV( 'No transpose', K-I, N-K+I, -TAU( I ), + $ V( I+1, 1 ), LDV, V( I, 1 ), LDV, ZERO, + $ T( I+1, I ), 1 ) + CALL ZLACGV( N-K+I-1, V( I, 1 ), LDV ) + V( I, N-K+I ) = VII + END IF +* +* T(i+1:k,i) := T(i+1:k,i+1:k) * T(i+1:k,i) +* + CALL ZTRMV( 'Lower', 'No transpose', 'Non-unit', K-I, + $ T( I+1, I+1 ), LDT, T( I+1, I ), 1 ) + END IF + T( I, I ) = TAU( I ) + END IF + 40 CONTINUE + END IF + RETURN +* +* End of ZLARFT +* + END |