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140 lines
3.6 KiB
C
140 lines
3.6 KiB
C
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#include "clapack.h"
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/* Table of constant values */
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static real c_b4 = 1.f;
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static real c_b5 = 0.f;
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static integer c__1 = 1;
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/* Subroutine */ int slarf_(char *side, integer *m, integer *n, real *v,
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integer *incv, real *tau, real *c__, integer *ldc, real *work)
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{
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/* System generated locals */
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integer c_dim1, c_offset;
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real r__1;
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/* Local variables */
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extern /* Subroutine */ int sger_(integer *, integer *, real *, real *,
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integer *, real *, integer *, real *, integer *);
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extern logical lsame_(char *, char *);
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extern /* Subroutine */ int sgemv_(char *, integer *, integer *, real *,
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real *, integer *, real *, integer *, real *, real *, integer *);
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/* -- LAPACK auxiliary 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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/* SLARF applies a real elementary reflector H to a real m by n matrix */
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/* C, from either the left or the right. H is represented in the form */
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/* H = I - tau * v * v' */
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/* where tau is a real scalar and v is a real vector. */
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/* If tau = 0, then H is taken to be the unit matrix. */
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/* Arguments */
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/* ========= */
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/* SIDE (input) CHARACTER*1 */
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/* = 'L': form H * C */
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/* = 'R': form C * H */
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/* M (input) INTEGER */
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/* The number of rows of the matrix C. */
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/* N (input) INTEGER */
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/* The number of columns of the matrix C. */
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/* V (input) REAL array, dimension */
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/* (1 + (M-1)*abs(INCV)) if SIDE = 'L' */
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/* or (1 + (N-1)*abs(INCV)) if SIDE = 'R' */
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/* The vector v in the representation of H. V is not used if */
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/* TAU = 0. */
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/* INCV (input) INTEGER */
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/* The increment between elements of v. INCV <> 0. */
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/* TAU (input) REAL */
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/* The value tau in the representation of H. */
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/* C (input/output) REAL array, dimension (LDC,N) */
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/* On entry, the m by n matrix C. */
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/* On exit, C is overwritten by the matrix H * C if SIDE = 'L', */
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/* or C * H if SIDE = 'R'. */
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/* LDC (input) INTEGER */
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/* The leading dimension of the array C. LDC >= max(1,M). */
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/* WORK (workspace) REAL array, dimension */
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/* (N) if SIDE = 'L' */
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/* or (M) if SIDE = 'R' */
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/* ===================================================================== */
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/* .. Parameters .. */
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/* .. */
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/* .. External Subroutines .. */
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/* .. */
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/* .. External Functions .. */
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/* .. */
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/* .. Executable Statements .. */
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/* Parameter adjustments */
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--v;
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c_dim1 = *ldc;
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c_offset = 1 + c_dim1;
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c__ -= c_offset;
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--work;
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/* Function Body */
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if (lsame_(side, "L")) {
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/* Form H * C */
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if (*tau != 0.f) {
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/* w := C' * v */
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sgemv_("Transpose", m, n, &c_b4, &c__[c_offset], ldc, &v[1], incv,
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&c_b5, &work[1], &c__1);
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/* C := C - v * w' */
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r__1 = -(*tau);
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sger_(m, n, &r__1, &v[1], incv, &work[1], &c__1, &c__[c_offset],
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ldc);
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}
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} else {
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/* Form C * H */
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if (*tau != 0.f) {
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/* w := C * v */
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sgemv_("No transpose", m, n, &c_b4, &c__[c_offset], ldc, &v[1],
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incv, &c_b5, &work[1], &c__1);
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/* C := C - w * v' */
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r__1 = -(*tau);
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sger_(m, n, &r__1, &work[1], &c__1, &v[1], incv, &c__[c_offset],
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ldc);
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}
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}
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return 0;
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/* End of SLARF */
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} /* slarf_ */
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