/* Copyright (c) 1992-2008 The University of Tennessee.  All rights reserved.
 * See file COPYING in this directory for details. */

#ifdef __cplusplus
extern "C" {
#endif

#include "f2c.h"
#include "hypre_lapack.h"

/* Subroutine */ integer dorglq_(integer *m, integer *n, integer *k, doublereal *
	a, integer *lda, doublereal *tau, doublereal *work, integer *lwork,
	integer *info)
{
/*  -- LAPACK routine (version 3.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       June 30, 1999


    Purpose
    =======

    DORGLQ generates an M-by-N real matrix Q with orthonormal rows,
    which is defined as the first M rows of a product of K elementary
    reflectors of order N

          Q  =  H(k) . . . H(2) H(1)

    as returned by DGELQF.

    Arguments
    =========

    M       (input) INTEGER
            The number of rows of the matrix Q. M >= 0.

    N       (input) INTEGER
            The number of columns of the matrix Q. N >= M.

    K       (input) INTEGER
            The number of elementary reflectors whose product defines the
            matrix Q. M >= K >= 0.

    A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
            On entry, the i-th row must contain the vector which defines
            the elementary reflector H(i), for i = 1,2,...,k, as returned
            by DGELQF in the first k rows of its array argument A.
            On exit, the M-by-N matrix Q.

    LDA     (input) INTEGER
            The first dimension of the array A. LDA >= max(1,M).

    TAU     (input) DOUBLE PRECISION array, dimension (K)
            TAU(i) must contain the scalar factor of the elementary
            reflector H(i), as returned by DGELQF.

    WORK    (workspace/output) DOUBLE PRECISION array, dimension (LWORK)
            On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

    LWORK   (input) INTEGER
            The dimension of the array WORK. LWORK >= max(1,M).
            For optimum performance LWORK >= M*NB, where NB is
            the optimal blocksize.

            If LWORK = -1, then a workspace query is assumed; the routine
            only calculates the optimal size of the WORK array, returns
            this value as the first entry of the WORK array, and no error
            message related to LWORK is issued by XERBLA.

    INFO    (output) INTEGER
            = 0:  successful exit
            < 0:  if INFO = -i, the i-th argument has an illegal value

    =====================================================================


       Test the input arguments

       Parameter adjustments */
    /* Table of constant values */
    integer c__1 = 1;
    integer c_n1 = -1;
    integer c__3 = 3;
    integer c__2 = 2;

    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2, i__3;
    /* Local variables */
    integer i__, j, l, nbmin, iinfo;
    extern /* Subroutine */ integer dorgl2_(integer *, integer *, integer *,
	    doublereal *, integer *, doublereal *, doublereal *, integer *);
    integer ib, nb, ki, kk;
    extern /* Subroutine */ integer dlarfb_(const char *,const char *,const char *,const char *,
	    integer *, integer *, integer *, doublereal *, integer *,
	    doublereal *, integer *, doublereal *, integer *, doublereal *,
	    integer *);
    integer nx;
    extern /* Subroutine */ integer dlarft_(const char *,const char *, integer *, integer *,
	    doublereal *, integer *, doublereal *, doublereal *, integer *), xerbla_(const char *, integer *);
    extern integer ilaenv_(integer *,const char *,const char *, integer *, integer *,
	    integer *, integer *, ftnlen, ftnlen);
    integer ldwork, lwkopt;
    logical lquery;
    integer iws;
#define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1]


    a_dim1 = *lda;
    a_offset = 1 + a_dim1 * 1;
    a -= a_offset;
    --tau;
    --work;

    /* Function Body */
    *info = 0;
    nb = ilaenv_(&c__1, "DORGLQ", " ", m, n, k, &c_n1, (ftnlen)6, (ftnlen)1);
    lwkopt = max(1,*m) * nb;
    work[1] = (doublereal) lwkopt;
    lquery = *lwork == -1;
    if (*m < 0) {
	*info = -1;
    } else if (*n < *m) {
	*info = -2;
    } else if (*k < 0 || *k > *m) {
	*info = -3;
    } else if (*lda < max(1,*m)) {
	*info = -5;
    } else if (*lwork < max(1,*m) && ! lquery) {
	*info = -8;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DORGLQ", &i__1);
	return 0;
    } else if (lquery) {
	return 0;
    }

/*     Quick return if possible */

    if (*m <= 0) {
	work[1] = 1.;
	return 0;
    }

    nbmin = 2;
    nx = 0;
    iws = *m;
    if (nb > 1 && nb < *k) {

/*        Determine when to cross over from blocked to unblocked code.

   Computing MAX */
	i__1 = 0, i__2 = ilaenv_(&c__3, "DORGLQ", " ", m, n, k, &c_n1, (
		ftnlen)6, (ftnlen)1);
	nx = max(i__1,i__2);
	if (nx < *k) {

/*           Determine if workspace is large enough for blocked code. */

	    ldwork = *m;
	    iws = ldwork * nb;
	    if (*lwork < iws) {

/*              Not enough workspace to use optimal NB:  reduce NB and
                determine the minimum value of NB. */

		nb = *lwork / ldwork;
/* Computing MAX */
		i__1 = 2, i__2 = ilaenv_(&c__2, "DORGLQ", " ", m, n, k, &c_n1,
			 (ftnlen)6, (ftnlen)1);
		nbmin = max(i__1,i__2);
	    }
	}
    }

    if (nb >= nbmin && nb < *k && nx < *k) {

/*        Use blocked code after the last block.
          The first kk rows are handled by the block method. */

	ki = (*k - nx - 1) / nb * nb;
/* Computing MIN */
	i__1 = *k, i__2 = ki + nb;
	kk = min(i__1,i__2);

/*        Set A(kk+1:m,1:kk) to zero. */

	i__1 = kk;
	for (j = 1; j <= i__1; ++j) {
	    i__2 = *m;
	    for (i__ = kk + 1; i__ <= i__2; ++i__) {
		a_ref(i__, j) = 0.;
/* L10: */
	    }
/* L20: */
	}
    } else {
	kk = 0;
    }

/*     Use unblocked code for the last or only block. */

    if (kk < *m) {
	i__1 = *m - kk;
	i__2 = *n - kk;
	i__3 = *k - kk;
	dorgl2_(&i__1, &i__2, &i__3, &a_ref(kk + 1, kk + 1), lda, &tau[kk + 1]
		, &work[1], &iinfo);
    }

    if (kk > 0) {

/*        Use blocked code */

	i__1 = -nb;
	for (i__ = ki + 1; i__1 < 0 ? i__ >= 1 : i__ <= 1; i__ += i__1) {
/* Computing MIN */
	    i__2 = nb, i__3 = *k - i__ + 1;
	    ib = min(i__2,i__3);
	    if (i__ + ib <= *m) {

/*              Form the triangular factor of the block reflector
                H = H(i) H(i+1) . . . H(i+ib-1) */

		i__2 = *n - i__ + 1;
		dlarft_("Forward", "Rowwise", &i__2, &ib, &a_ref(i__, i__),
			lda, &tau[i__], &work[1], &ldwork);

/*              Apply H' to A(i+ib:m,i:n) from the right */

		i__2 = *m - i__ - ib + 1;
		i__3 = *n - i__ + 1;
		dlarfb_("Right", "Transpose", "Forward", "Rowwise", &i__2, &
			i__3, &ib, &a_ref(i__, i__), lda, &work[1], &ldwork, &
			a_ref(i__ + ib, i__), lda, &work[ib + 1], &ldwork);
	    }

/*           Apply H' to columns i:n of current block */

	    i__2 = *n - i__ + 1;
	    dorgl2_(&ib, &i__2, &ib, &a_ref(i__, i__), lda, &tau[i__], &work[
		    1], &iinfo);

/*           Set columns 1:i-1 of current block to zero */

	    i__2 = i__ - 1;
	    for (j = 1; j <= i__2; ++j) {
		i__3 = i__ + ib - 1;
		for (l = i__; l <= i__3; ++l) {
		    a_ref(l, j) = 0.;
/* L30: */
		}
/* L40: */
	    }
/* L50: */
	}
    }

    work[1] = (doublereal) iws;
    return 0;

/*     End of DORGLQ */

} /* dorglq_ */

#undef a_ref

#ifdef __cplusplus
}
#endif
