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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 DORGL2 + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dorgl2.f">
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dorgl2.f">
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dorgl2.f">
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* SUBROUTINE DORGL2( M, N, K, A, LDA, TAU, WORK, INFO )
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* .. Scalar Arguments ..
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* INTEGER INFO, K, LDA, M, N
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* .. Array Arguments ..
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* DOUBLE PRECISION A( LDA, * ), TAU( * ), WORK( * )
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*> DORGL2 generates an m by n real matrix Q with orthonormal rows,
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*> which is defined as the first m rows of a product of k elementary
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*> reflectors of order n
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*> Q = H(k) . . . H(2) H(1)
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*> as returned by DGELQF.
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*> The number of rows of the matrix Q. M >= 0.
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*> The number of columns of the matrix Q. N >= M.
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*> The number of elementary reflectors whose product defines the
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*> matrix Q. M >= K >= 0.
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*> A is DOUBLE PRECISION array, dimension (LDA,N)
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*> On entry, the i-th row must contain the vector which defines
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*> the elementary reflector H(i), for i = 1,2,...,k, as returned
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*> by DGELQF in the first k rows of its array argument A.
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*> On exit, the m-by-n matrix Q.
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*> The first dimension of the array A. LDA >= max(1,M).
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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 DGELQF.
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*> WORK is DOUBLE PRECISION array, dimension (M)
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*> = 0: successful exit
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*> < 0: if INFO = -i, the i-th argument has 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 DORGL2( M, N, K, A, LDA, TAU, WORK, 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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INTEGER INFO, K, LDA, M, N
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* .. Array Arguments ..
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DOUBLE PRECISION A( LDA, * ), TAU( * ), WORK( * )
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* =====================================================================
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DOUBLE PRECISION ONE, ZERO
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PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 )
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* .. Local Scalars ..
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* .. External Subroutines ..
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EXTERNAL DLARF, DSCAL, 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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ELSE IF( N.LT.M ) THEN
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ELSE IF( K.LT.0 .OR. K.GT.M ) THEN
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ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
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CALL XERBLA( 'DORGL2', -INFO )
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* Quick return if possible
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* Initialise rows k+1:m to rows of the unit matrix
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IF( J.GT.K .AND. J.LE.M )
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* Apply H(i) to A(i:m,i:n) from the right
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CALL DLARF( 'Right', M-I, N-I+1, A( I, I ), LDA,
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$ TAU( I ), A( I+1, I ), LDA, WORK )
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CALL DSCAL( N-I, -TAU( I ), A( I, I+1 ), LDA )
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A( I, I ) = ONE - TAU( I )
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* Set A(i,1:i-1) to zero