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diff --git a/eigen/lapack/slarft.f b/eigen/lapack/slarft.f new file mode 100644 index 0000000..30b0668 --- /dev/null +++ b/eigen/lapack/slarft.f @@ -0,0 +1,326 @@ +*> \brief \b SLARFT +* +* =========== DOCUMENTATION =========== +* +* Online html documentation available at +* http://www.netlib.org/lapack/explore-html/ +* +*> \htmlonly +*> Download SLARFT + dependencies +*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slarft.f"> +*> [TGZ]</a> +*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/slarft.f"> +*> [ZIP]</a> +*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slarft.f"> +*> [TXT]</a> +*> \endhtmlonly +* +* Definition: +* =========== +* +* SUBROUTINE SLARFT( DIRECT, STOREV, N, K, V, LDV, TAU, T, LDT ) +* +* .. Scalar Arguments .. +* CHARACTER DIRECT, STOREV +* INTEGER K, LDT, LDV, N +* .. +* .. Array Arguments .. +* REAL T( LDT, * ), TAU( * ), V( LDV, * ) +* .. +* +* +*> \par Purpose: +* ============= +*> +*> \verbatim +*> +*> SLARFT forms the triangular factor T of a real 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**T +*> +*> 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 * T * V +*> \endverbatim +* +* Arguments: +* ========== +* +*> \param[in] DIRECT +*> \verbatim +*> DIRECT is 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) +*> \endverbatim +*> +*> \param[in] STOREV +*> \verbatim +*> STOREV is CHARACTER*1 +*> Specifies how the vectors which define the elementary +*> reflectors are stored (see also Further Details): +*> = 'C': columnwise +*> = 'R': rowwise +*> \endverbatim +*> +*> \param[in] N +*> \verbatim +*> N is INTEGER +*> The order of the block reflector H. N >= 0. +*> \endverbatim +*> +*> \param[in] K +*> \verbatim +*> K is INTEGER +*> The order of the triangular factor T (= the number of +*> elementary reflectors). K >= 1. +*> \endverbatim +*> +*> \param[in] V +*> \verbatim +*> V is REAL array, dimension +*> (LDV,K) if STOREV = 'C' +*> (LDV,N) if STOREV = 'R' +*> The matrix V. See further details. +*> \endverbatim +*> +*> \param[in] LDV +*> \verbatim +*> LDV is INTEGER +*> The leading dimension of the array V. +*> If STOREV = 'C', LDV >= max(1,N); if STOREV = 'R', LDV >= K. +*> \endverbatim +*> +*> \param[in] TAU +*> \verbatim +*> TAU is REAL array, dimension (K) +*> TAU(i) must contain the scalar factor of the elementary +*> reflector H(i). +*> \endverbatim +*> +*> \param[out] T +*> \verbatim +*> T is REAL 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. +*> \endverbatim +*> +*> \param[in] LDT +*> \verbatim +*> LDT is INTEGER +*> The leading dimension of the array T. LDT >= K. +*> \endverbatim +* +* Authors: +* ======== +* +*> \author Univ. of Tennessee +*> \author Univ. of California Berkeley +*> \author Univ. of Colorado Denver +*> \author NAG Ltd. +* +*> \date April 2012 +* +*> \ingroup realOTHERauxiliary +* +*> \par Further Details: +* ===================== +*> +*> \verbatim +*> +*> 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. +*> +*> 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 ) +*> \endverbatim +*> +* ===================================================================== + SUBROUTINE SLARFT( DIRECT, STOREV, N, K, V, LDV, TAU, T, LDT ) +* +* -- LAPACK auxiliary routine (version 3.4.1) -- +* -- LAPACK is a software package provided by Univ. of Tennessee, -- +* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- +* April 2012 +* +* .. Scalar Arguments .. + CHARACTER DIRECT, STOREV + INTEGER K, LDT, LDV, N +* .. +* .. Array Arguments .. + REAL T( LDT, * ), TAU( * ), V( LDV, * ) +* .. +* +* ===================================================================== +* +* .. Parameters .. + REAL ONE, ZERO + PARAMETER ( ONE = 1.0E+0, ZERO = 0.0E+0 ) +* .. +* .. Local Scalars .. + INTEGER I, J, PREVLASTV, LASTV +* .. +* .. External Subroutines .. + EXTERNAL SGEMV, STRMV +* .. +* .. External Functions .. + LOGICAL LSAME + EXTERNAL LSAME +* .. +* .. Executable Statements .. +* +* Quick return if possible +* + IF( N.EQ.0 ) + $ RETURN +* + IF( LSAME( DIRECT, 'F' ) ) THEN + PREVLASTV = N + DO I = 1, K + PREVLASTV = MAX( I, PREVLASTV ) + IF( TAU( I ).EQ.ZERO ) THEN +* +* H(i) = I +* + DO J = 1, I + T( J, I ) = ZERO + END DO + ELSE +* +* general case +* + IF( LSAME( STOREV, 'C' ) ) THEN +* Skip any trailing zeros. + DO LASTV = N, I+1, -1 + IF( V( LASTV, I ).NE.ZERO ) EXIT + END DO + DO J = 1, I-1 + T( J, I ) = -TAU( I ) * V( I , J ) + END DO + J = MIN( LASTV, PREVLASTV ) +* +* T(1:i-1,i) := - tau(i) * V(i:j,1:i-1)**T * V(i:j,i) +* + CALL SGEMV( 'Transpose', J-I, I-1, -TAU( I ), + $ V( I+1, 1 ), LDV, V( I+1, I ), 1, ONE, + $ T( 1, I ), 1 ) + ELSE +* Skip any trailing zeros. + DO LASTV = N, I+1, -1 + IF( V( I, LASTV ).NE.ZERO ) EXIT + END DO + DO J = 1, I-1 + T( J, I ) = -TAU( I ) * V( J , I ) + END DO + J = MIN( LASTV, PREVLASTV ) +* +* T(1:i-1,i) := - tau(i) * V(1:i-1,i:j) * V(i,i:j)**T +* + CALL SGEMV( 'No transpose', I-1, J-I, -TAU( I ), + $ V( 1, I+1 ), LDV, V( I, I+1 ), LDV, + $ ONE, T( 1, I ), 1 ) + END IF +* +* T(1:i-1,i) := T(1:i-1,1:i-1) * T(1:i-1,i) +* + CALL STRMV( 'Upper', 'No transpose', 'Non-unit', I-1, T, + $ LDT, T( 1, I ), 1 ) + T( I, I ) = TAU( I ) + IF( I.GT.1 ) THEN + PREVLASTV = MAX( PREVLASTV, LASTV ) + ELSE + PREVLASTV = LASTV + END IF + END IF + END DO + ELSE + PREVLASTV = 1 + DO I = K, 1, -1 + IF( TAU( I ).EQ.ZERO ) THEN +* +* H(i) = I +* + DO J = I, K + T( J, I ) = ZERO + END DO + ELSE +* +* general case +* + IF( I.LT.K ) THEN + IF( LSAME( STOREV, 'C' ) ) THEN +* Skip any leading zeros. + DO LASTV = 1, I-1 + IF( V( LASTV, I ).NE.ZERO ) EXIT + END DO + DO J = I+1, K + T( J, I ) = -TAU( I ) * V( N-K+I , J ) + END DO + J = MAX( LASTV, PREVLASTV ) +* +* T(i+1:k,i) = -tau(i) * V(j:n-k+i,i+1:k)**T * V(j:n-k+i,i) +* + CALL SGEMV( 'Transpose', N-K+I-J, K-I, -TAU( I ), + $ V( J, I+1 ), LDV, V( J, I ), 1, ONE, + $ T( I+1, I ), 1 ) + ELSE +* Skip any leading zeros. + DO LASTV = 1, I-1 + IF( V( I, LASTV ).NE.ZERO ) EXIT + END DO + DO J = I+1, K + T( J, I ) = -TAU( I ) * V( J, N-K+I ) + END DO + J = MAX( LASTV, PREVLASTV ) +* +* T(i+1:k,i) = -tau(i) * V(i+1:k,j:n-k+i) * V(i,j:n-k+i)**T +* + CALL SGEMV( 'No transpose', K-I, N-K+I-J, + $ -TAU( I ), V( I+1, J ), LDV, V( I, J ), LDV, + $ ONE, T( I+1, I ), 1 ) + END IF +* +* T(i+1:k,i) := T(i+1:k,i+1:k) * T(i+1:k,i) +* + CALL STRMV( 'Lower', 'No transpose', 'Non-unit', K-I, + $ T( I+1, I+1 ), LDT, T( I+1, I ), 1 ) + IF( I.GT.1 ) THEN + PREVLASTV = MIN( PREVLASTV, LASTV ) + ELSE + PREVLASTV = LASTV + END IF + END IF + T( I, I ) = TAU( I ) + END IF + END DO + END IF + RETURN +* +* End of SLARFT +* + END |