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163 lines
4.0 KiB
C
163 lines
4.0 KiB
C
#include "clapack.h"
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/* Table of constant values */
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static integer c__1 = 1;
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/* Subroutine */ int sorg2r_(integer *m, integer *n, integer *k, real *a,
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integer *lda, real *tau, real *work, integer *info)
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{
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/* System generated locals */
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integer a_dim1, a_offset, i__1, i__2;
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real r__1;
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/* Local variables */
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integer i__, j, l;
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extern /* Subroutine */ int sscal_(integer *, real *, real *, integer *),
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slarf_(char *, integer *, integer *, real *, integer *, real *,
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real *, integer *, real *), xerbla_(char *, integer *);
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/* -- LAPACK routine (version 3.1) -- */
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/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
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/* November 2006 */
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/* .. Scalar Arguments .. */
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/* .. */
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/* .. Array Arguments .. */
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/* .. */
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/* Purpose */
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/* ======= */
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/* SORG2R generates an m by n real matrix Q with orthonormal columns, */
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/* which is defined as the first n columns of a product of k elementary */
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/* reflectors of order m */
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/* Q = H(1) H(2) . . . H(k) */
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/* as returned by SGEQRF. */
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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. M >= N >= 0. */
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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. N >= K >= 0. */
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/* A (input/output) REAL array, dimension (LDA,N) */
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/* On entry, the i-th column must contain the vector which */
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/* defines the elementary reflector H(i), for i = 1,2,...,k, as */
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/* returned by SGEQRF in the first k columns of its array */
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/* 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) REAL 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 SGEQRF. */
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/* WORK (workspace) REAL array, dimension (N) */
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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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/* .. Parameters .. */
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/* .. */
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/* .. Local Scalars .. */
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/* .. */
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/* .. External Subroutines .. */
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/* .. */
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/* .. Intrinsic Functions .. */
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/* .. */
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/* .. Executable Statements .. */
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/* Test the input arguments */
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/* Parameter adjustments */
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a_dim1 = *lda;
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a_offset = 1 + a_dim1;
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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 < 0 || *n > *m) {
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*info = -2;
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} else if (*k < 0 || *k > *n) {
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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_("SORG2R", &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 (*n <= 0) {
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return 0;
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}
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/* Initialise columns k+1:n to columns of the unit matrix */
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i__1 = *n;
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for (j = *k + 1; j <= i__1; ++j) {
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i__2 = *m;
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for (l = 1; l <= i__2; ++l) {
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a[l + j * a_dim1] = 0.f;
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/* L10: */
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}
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a[j + j * a_dim1] = 1.f;
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/* L20: */
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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 left */
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if (i__ < *n) {
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a[i__ + i__ * a_dim1] = 1.f;
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i__1 = *m - i__ + 1;
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i__2 = *n - i__;
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slarf_("Left", &i__1, &i__2, &a[i__ + i__ * a_dim1], &c__1, &tau[
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i__], &a[i__ + (i__ + 1) * a_dim1], lda, &work[1]);
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}
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if (i__ < *m) {
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i__1 = *m - i__;
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r__1 = -tau[i__];
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sscal_(&i__1, &r__1, &a[i__ + 1 + i__ * a_dim1], &c__1);
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}
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a[i__ + i__ * a_dim1] = 1.f - tau[i__];
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/* Set A(1:i-1,i) 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[l + i__ * a_dim1] = 0.f;
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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 SORG2R */
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} /* sorg2r_ */
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