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162 lines
4.0 KiB
162 lines
4.0 KiB
#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 dorg2r_(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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/* 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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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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/* -- 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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/* DORG2R 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 DGEQRF. */ |
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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) DOUBLE PRECISION 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 DGEQRF 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) 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 DGEQRF. */ |
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/* WORK (workspace) DOUBLE PRECISION 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_("DORG2R", &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.; |
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/* L10: */ |
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} |
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a[j + j * a_dim1] = 1.; |
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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.; |
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i__1 = *m - i__ + 1; |
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i__2 = *n - i__; |
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dlarf_("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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d__1 = -tau[i__]; |
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dscal_(&i__1, &d__1, &a[i__ + 1 + i__ * a_dim1], &c__1); |
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} |
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a[i__ + i__ * a_dim1] = 1. - 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.; |
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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 DORG2R */ |
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} /* dorg2r_ */
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