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/* lapack/double/dorgr2.f -- translated by f2c (version 20050501).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
#ifdef __cplusplus
extern "C" {
#endif
#include "v3p_netlib.h"
/*< SUBROUTINE DORGR2( M, N, K, A, LDA, TAU, WORK, INFO ) >*/
/* Subroutine */ int dorgr2_(integer *m, integer *n, integer *k, doublereal *
a, integer *lda, doublereal *tau, doublereal *work, integer *info)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2, i__3;
doublereal d__1;
/* Local variables */
integer i__, j, l, ii;
extern /* Subroutine */ int dscal_(integer *, doublereal *, doublereal *,
integer *), dlarf_(char *, integer *, integer *, doublereal *,
integer *, doublereal *, doublereal *, integer *, doublereal *,
ftnlen), xerbla_(char *, integer *, ftnlen);
/* -- 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 */
/* .. Scalar Arguments .. */
/*< INTEGER INFO, K, LDA, M, N >*/
/* .. */
/* .. Array Arguments .. */
/*< DOUBLE PRECISION A( LDA, * ), TAU( * ), WORK( * ) >*/
/* .. */
/* Purpose */
/* ======= */
/* DORGR2 generates an m by n real matrix Q with orthonormal rows, */
/* which is defined as the last m rows of a product of k elementary */
/* reflectors of order n */
/* Q = H(1) H(2) . . . H(k) */
/* as returned by DGERQF. */
/* 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 (m-k+i)-th row must contain the vector which */
/* defines the elementary reflector H(i), for i = 1,2,...,k, as */
/* returned by DGERQF in the last 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 DGERQF. */
/* WORK (workspace) DOUBLE PRECISION array, dimension (M) */
/* INFO (output) INTEGER */
/* = 0: successful exit */
/* < 0: if INFO = -i, the i-th argument has an illegal value */
/* ===================================================================== */
/* .. Parameters .. */
/*< DOUBLE PRECISION ONE, ZERO >*/
/*< PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 ) >*/
/* .. */
/* .. Local Scalars .. */
/*< INTEGER I, II, J, L >*/
/* .. */
/* .. External Subroutines .. */
/*< EXTERNAL DLARF, DSCAL, XERBLA >*/
/* .. */
/* .. Intrinsic Functions .. */
/*< INTRINSIC MAX >*/
/* .. */
/* .. Executable Statements .. */
/* Test the input arguments */
/*< INFO = 0 >*/
/* Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--tau;
--work;
/* Function Body */
*info = 0;
/*< IF( M.LT.0 ) THEN >*/
if (*m < 0) {
/*< INFO = -1 >*/
*info = -1;
/*< ELSE IF( N.LT.M ) THEN >*/
} else if (*n < *m) {
/*< INFO = -2 >*/
*info = -2;
/*< ELSE IF( K.LT.0 .OR. K.GT.M ) THEN >*/
} else if (*k < 0 || *k > *m) {
/*< INFO = -3 >*/
*info = -3;
/*< ELSE IF( LDA.LT.MAX( 1, M ) ) THEN >*/
} else if (*lda < max(1,*m)) {
/*< INFO = -5 >*/
*info = -5;
/*< END IF >*/
}
/*< IF( INFO.NE.0 ) THEN >*/
if (*info != 0) {
/*< CALL XERBLA( 'DORGR2', -INFO ) >*/
i__1 = -(*info);
xerbla_("DORGR2", &i__1, (ftnlen)6);
/*< RETURN >*/
return 0;
/*< END IF >*/
}
/* Quick return if possible */
/*< >*/
if (*m <= 0) {
return 0;
}
/*< IF( K.LT.M ) THEN >*/
if (*k < *m) {
/* Initialise rows 1:m-k to rows of the unit matrix */
/*< DO 20 J = 1, N >*/
i__1 = *n;
for (j = 1; j <= i__1; ++j) {
/*< DO 10 L = 1, M - K >*/
i__2 = *m - *k;
for (l = 1; l <= i__2; ++l) {
/*< A( L, J ) = ZERO >*/
a[l + j * a_dim1] = 0.;
/*< 10 CONTINUE >*/
/* L10: */
}
/*< >*/
if (j > *n - *m && j <= *n - *k) {
a[*m - *n + j + j * a_dim1] = 1.;
}
/*< 20 CONTINUE >*/
/* L20: */
}
/*< END IF >*/
}
/*< DO 40 I = 1, K >*/
i__1 = *k;
for (i__ = 1; i__ <= i__1; ++i__) {
/*< II = M - K + I >*/
ii = *m - *k + i__;
/* Apply H(i) to A(1:m-k+i,1:n-k+i) from the right */
/*< A( II, N-M+II ) = ONE >*/
a[ii + (*n - *m + ii) * a_dim1] = 1.;
/*< >*/
i__2 = ii - 1;
i__3 = *n - *m + ii;
dlarf_("Right", &i__2, &i__3, &a[ii + a_dim1], lda, &tau[i__], &a[
a_offset], lda, &work[1], (ftnlen)5);
/*< CALL DSCAL( N-M+II-1, -TAU( I ), A( II, 1 ), LDA ) >*/
i__2 = *n - *m + ii - 1;
d__1 = -tau[i__];
dscal_(&i__2, &d__1, &a[ii + a_dim1], lda);
/*< A( II, N-M+II ) = ONE - TAU( I ) >*/
a[ii + (*n - *m + ii) * a_dim1] = 1. - tau[i__];
/* Set A(m-k+i,n-k+i+1:n) to zero */
/*< DO 30 L = N - M + II + 1, N >*/
i__2 = *n;
for (l = *n - *m + ii + 1; l <= i__2; ++l) {
/*< A( II, L ) = ZERO >*/
a[ii + l * a_dim1] = 0.;
/*< 30 CONTINUE >*/
/* L30: */
}
/*< 40 CONTINUE >*/
/* L40: */
}
/*< RETURN >*/
return 0;
/* End of DORGR2 */
/*< END >*/
} /* dorgr2_ */
#ifdef __cplusplus
}
#endif
|
