/* 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 dorg2r_(integer *m, integer *n, integer *k, doublereal *
	a, integer *lda, doublereal *tau, doublereal *work, integer *info)
{
/*  -- LAPACK routine (version 3.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       February 29, 1992


    Purpose
    =======

    DORG2R generates an m by n real matrix Q with orthonormal columns,
    which is defined as the first n columns of a product of k elementary
    reflectors of order m

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

    as returned by DGEQRF.

    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. M >= N >= 0.

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

    A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
            On entry, the i-th column must contain the vector which
            defines the elementary reflector H(i), for i = 1,2,...,k, as
            returned by DGEQRF in the first k columns 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 DGEQRF.

    WORK    (workspace) DOUBLE PRECISION array, dimension (N)

    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;

    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2;
    doublereal d__1;
    /* Local variables */
    integer i__, j, l;
    extern /* Subroutine */ integer dscal_(integer *, doublereal *, doublereal *,
	    integer *), dlarf_(const char *, integer *, integer *, doublereal *,
	    integer *, doublereal *, doublereal *, integer *, doublereal *), xerbla_(const char *, integer *);
#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;
    if (*m < 0) {
	*info = -1;
    } else if (*n < 0 || *n > *m) {
	*info = -2;
    } else if (*k < 0 || *k > *n) {
	*info = -3;
    } else if (*lda < max(1,*m)) {
	*info = -5;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DORG2R", &i__1);
	return 0;
    }

/*     Quick return if possible */

    if (*n <= 0) {
	return 0;
    }

/*     Initialise columns k+1:n to columns of the unit matrix */

    i__1 = *n;
    for (j = *k + 1; j <= i__1; ++j) {
	i__2 = *m;
	for (l = 1; l <= i__2; ++l) {
	    a_ref(l, j) = 0.;
/* L10: */
	}
	a_ref(j, j) = 1.;
/* L20: */
    }

    for (i__ = *k; i__ >= 1; --i__) {

/*        Apply H(i) to A(i:m,i:n) from the left */

	if (i__ < *n) {
	    a_ref(i__, i__) = 1.;
	    i__1 = *m - i__ + 1;
	    i__2 = *n - i__;
	    dlarf_("Left", &i__1, &i__2, &a_ref(i__, i__), &c__1, &tau[i__], &
		    a_ref(i__, i__ + 1), lda, &work[1]);
	}
	if (i__ < *m) {
	    i__1 = *m - i__;
	    d__1 = -tau[i__];
	    dscal_(&i__1, &d__1, &a_ref(i__ + 1, i__), &c__1);
	}
	a_ref(i__, i__) = 1. - tau[i__];

/*        Set A(1:i-1,i) to zero */

	i__1 = i__ - 1;
	for (l = 1; l <= i__1; ++l) {
	    a_ref(l, i__) = 0.;
/* L30: */
	}
/* L40: */
    }
    return 0;

/*     End of DORG2R */

} /* dorg2r_ */

#undef a_ref

#ifdef __cplusplus
}
#endif
