155 lines
3.8 KiB
C
155 lines
3.8 KiB
C
#include "hypre_lapack.h"
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#include "f2c.h"
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/* Subroutine */ int dorgl2_(integer *m, integer *n, integer *k, doublereal *
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a, integer *lda, doublereal *tau, doublereal *work, integer *info)
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{
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/* -- LAPACK routine (version 3.0) --
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Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
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Courant Institute, Argonne National Lab, and Rice University
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June 30, 1999
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Purpose
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=======
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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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Arguments
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=========
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M (input) INTEGER
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The number of rows of the matrix Q. M >= 0.
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N (input) INTEGER
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The number of columns of the matrix Q. N >= M.
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K (input) INTEGER
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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 (input/output) 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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LDA (input) INTEGER
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The first dimension of the array A. LDA >= max(1,M).
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TAU (input) 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 (workspace) DOUBLE PRECISION array, dimension (M)
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INFO (output) INTEGER
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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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=====================================================================
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Test the input arguments
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Parameter adjustments */
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/* System generated locals */
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integer a_dim1, a_offset, i__1, i__2;
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doublereal d__1;
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/* Local variables */
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static integer i__, j, l;
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extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *,
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integer *), dlarf_(char *, integer *, integer *, doublereal *,
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integer *, doublereal *, doublereal *, integer *, doublereal *), xerbla_(char *, integer *);
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#define a_ref(a_1,a_2) a[(a_2)*a_dim1 + a_1]
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a_dim1 = *lda;
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a_offset = 1 + a_dim1 * 1;
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a -= a_offset;
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--tau;
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--work;
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/* Function Body */
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*info = 0;
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if (*m < 0) {
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*info = -1;
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} else if (*n < *m) {
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*info = -2;
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} else if (*k < 0 || *k > *m) {
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*info = -3;
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} else if (*lda < max(1,*m)) {
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*info = -5;
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}
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if (*info != 0) {
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i__1 = -(*info);
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xerbla_("DORGL2", &i__1);
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return 0;
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}
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/* Quick return if possible */
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if (*m <= 0) {
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return 0;
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}
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if (*k < *m) {
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/* Initialise rows k+1:m to rows of the unit matrix */
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i__1 = *n;
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for (j = 1; j <= i__1; ++j) {
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i__2 = *m;
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for (l = *k + 1; l <= i__2; ++l) {
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a_ref(l, j) = 0.;
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/* L10: */
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}
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if (j > *k && j <= *m) {
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a_ref(j, j) = 1.;
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}
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/* L20: */
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}
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}
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for (i__ = *k; i__ >= 1; --i__) {
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/* Apply H(i) to A(i:m,i:n) from the right */
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if (i__ < *n) {
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if (i__ < *m) {
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a_ref(i__, i__) = 1.;
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i__1 = *m - i__;
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i__2 = *n - i__ + 1;
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dlarf_("Right", &i__1, &i__2, &a_ref(i__, i__), lda, &tau[i__]
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, &a_ref(i__ + 1, i__), lda, &work[1]);
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}
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i__1 = *n - i__;
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d__1 = -tau[i__];
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dscal_(&i__1, &d__1, &a_ref(i__, i__ + 1), lda);
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}
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a_ref(i__, i__) = 1. - tau[i__];
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/* Set A(i,1:i-1) to zero */
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i__1 = i__ - 1;
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for (l = 1; l <= i__1; ++l) {
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a_ref(i__, l) = 0.;
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/* L30: */
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}
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/* L40: */
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}
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return 0;
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/* End of DORGL2 */
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} /* dorgl2_ */
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#undef a_ref
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