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* =========== DOCUMENTATION ===========
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* Online html documentation available at
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* http://www.netlib.org/lapack/explore-html/
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*> Download DORMQR + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dormqr.f">
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dormqr.f">
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dormqr.f">
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* SUBROUTINE DORMQR( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC,
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* .. Scalar Arguments ..
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* CHARACTER SIDE, TRANS
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* INTEGER INFO, K, LDA, LDC, LWORK, M, N
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* .. Array Arguments ..
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* DOUBLE PRECISION A( LDA, * ), C( LDC, * ), TAU( * ), WORK( * )
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*> DORMQR overwrites the general real M-by-N matrix C with
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*> SIDE = 'L' SIDE = 'R'
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*> TRANS = 'N': Q * C C * Q
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*> TRANS = 'T': Q**T * C C * Q**T
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*> where Q is a real orthogonal matrix defined as the product of k
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*> elementary reflectors
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*> Q = H(1) H(2) . . . H(k)
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*> as returned by DGEQRF. Q is of order M if SIDE = 'L' and of order N
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*> SIDE is CHARACTER*1
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*> = 'L': apply Q or Q**T from the Left;
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*> = 'R': apply Q or Q**T from the Right.
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*> TRANS is CHARACTER*1
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*> = 'N': No transpose, apply Q;
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*> = 'T': Transpose, apply Q**T.
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*> The number of rows of the matrix C. M >= 0.
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*> The number of columns of the matrix C. N >= 0.
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*> The number of elementary reflectors whose product defines
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*> If SIDE = 'L', M >= K >= 0;
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*> if SIDE = 'R', N >= K >= 0.
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*> A is DOUBLE PRECISION array, dimension (LDA,K)
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*> The i-th column must contain the vector which defines the
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*> elementary reflector H(i), for i = 1,2,...,k, as returned by
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*> DGEQRF in the first k columns of its array argument A.
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*> The leading dimension of the array A.
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*> If SIDE = 'L', LDA >= max(1,M);
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*> if SIDE = 'R', LDA >= max(1,N).
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*> TAU is DOUBLE PRECISION array, dimension (K)
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*> TAU(i) must contain the scalar factor of the elementary
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*> reflector H(i), as returned by DGEQRF.
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*> C is DOUBLE PRECISION array, dimension (LDC,N)
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*> On entry, the M-by-N matrix C.
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*> On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.
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*> The leading dimension of the array C. LDC >= max(1,M).
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*> WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
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*> On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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*> The dimension of the array WORK.
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*> If SIDE = 'L', LWORK >= max(1,N);
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*> if SIDE = 'R', LWORK >= max(1,M).
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*> For optimum performance LWORK >= N*NB if SIDE = 'L', and
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*> LWORK >= M*NB if SIDE = 'R', where NB is the optimal
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*> If LWORK = -1, then a workspace query is assumed; the routine
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*> only calculates the optimal size of the WORK array, returns
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*> this value as the first entry of the WORK array, and no error
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*> message related to LWORK is issued by XERBLA.
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*> = 0: successful exit
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*> < 0: if INFO = -i, the i-th argument had an illegal value
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \date November 2011
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*> \ingroup doubleOTHERcomputational
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* =====================================================================
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SUBROUTINE DORMQR( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC,
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$ WORK, LWORK, INFO )
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* -- LAPACK computational routine (version 3.4.0) --
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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* .. Scalar Arguments ..
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CHARACTER SIDE, TRANS
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INTEGER INFO, K, LDA, LDC, LWORK, M, N
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* .. Array Arguments ..
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DOUBLE PRECISION A( LDA, * ), C( LDC, * ), TAU( * ), WORK( * )
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* =====================================================================
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PARAMETER ( NBMAX = 64, LDT = NBMAX+1 )
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* .. Local Scalars ..
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LOGICAL LEFT, LQUERY, NOTRAN
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INTEGER I, I1, I2, I3, IB, IC, IINFO, IWS, JC, LDWORK,
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$ LWKOPT, MI, NB, NBMIN, NI, NQ, NW
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DOUBLE PRECISION T( LDT, NBMAX )
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* .. External Functions ..
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EXTERNAL LSAME, ILAENV
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* .. External Subroutines ..
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EXTERNAL DLARFB, DLARFT, DORM2R, XERBLA
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* .. Intrinsic Functions ..
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* .. Executable Statements ..
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* Test the input arguments
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LEFT = LSAME( SIDE, 'L' )
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NOTRAN = LSAME( TRANS, 'N' )
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LQUERY = ( LWORK.EQ.-1 )
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* NQ is the order of Q and NW is the minimum dimension of WORK
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IF( .NOT.LEFT .AND. .NOT.LSAME( SIDE, 'R' ) ) THEN
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ELSE IF( .NOT.NOTRAN .AND. .NOT.LSAME( TRANS, 'T' ) ) THEN
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ELSE IF( M.LT.0 ) THEN
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ELSE IF( N.LT.0 ) THEN
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ELSE IF( K.LT.0 .OR. K.GT.NQ ) THEN
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ELSE IF( LDA.LT.MAX( 1, NQ ) ) THEN
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ELSE IF( LDC.LT.MAX( 1, M ) ) THEN
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ELSE IF( LWORK.LT.MAX( 1, NW ) .AND. .NOT.LQUERY ) THEN
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* Determine the block size. NB may be at most NBMAX, where NBMAX
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* is used to define the local array T.
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NB = MIN( NBMAX, ILAENV( 1, 'DORMQR', SIDE // TRANS, M, N, K,
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LWKOPT = MAX( 1, NW )*NB
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CALL XERBLA( 'DORMQR', -INFO )
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ELSE IF( LQUERY ) THEN
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* Quick return if possible
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IF( M.EQ.0 .OR. N.EQ.0 .OR. K.EQ.0 ) THEN
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IF( NB.GT.1 .AND. NB.LT.K ) THEN
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IF( LWORK.LT.IWS ) THEN
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NBMIN = MAX( 2, ILAENV( 2, 'DORMQR', SIDE // TRANS, M, N, K,
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IF( NB.LT.NBMIN .OR. NB.GE.K ) THEN
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CALL DORM2R( SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK,
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IF( ( LEFT .AND. .NOT.NOTRAN ) .OR.
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$ ( .NOT.LEFT .AND. NOTRAN ) ) THEN
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I1 = ( ( K-1 ) / NB )*NB + 1
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IB = MIN( NB, K-I+1 )
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* Form the triangular factor of the block reflector
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* H = H(i) H(i+1) . . . H(i+ib-1)
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CALL DLARFT( 'Forward', 'Columnwise', NQ-I+1, IB, A( I, I ),
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$ LDA, TAU( I ), T, LDT )
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* H or H**T is applied to C(i:m,1:n)
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* H or H**T is applied to C(1:m,i:n)
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CALL DLARFB( SIDE, TRANS, 'Forward', 'Columnwise', MI, NI,
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$ IB, A( I, I ), LDA, T, LDT, C( IC, JC ), LDC,