?? slarf.c
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/** ======================================================================* NIST Guide to Available Math Software.* Fullsource for module SSYEVX.C from package CLAPACK.* Retrieved from NETLIB on Fri Mar 10 14:23:44 2000.* ======================================================================*/#include <f2c.h>/* Subroutine */ int slarf_(char *side, integer *m, integer *n, real *v, integer *incv, real *tau, real *c, integer *ldc, real *work){/* -- LAPACK auxiliary routine (version 2.0) -- Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., Courant Institute, Argonne National Lab, and Rice University February 29, 1992 Purpose ======= SLARF applies a real elementary reflector H to a real m by n matrix C, from either the left or the right. H is represented in the form H = I - tau * v * v' where tau is a real scalar and v is a real vector. If tau = 0, then H is taken to be the unit matrix. Arguments ========= SIDE (input) CHARACTER*1 = 'L': form H * C = 'R': form C * H M (input) INTEGER The number of rows of the matrix C. N (input) INTEGER The number of columns of the matrix C. V (input) REAL array, dimension (1 + (M-1)*abs(INCV)) if SIDE = 'L' or (1 + (N-1)*abs(INCV)) if SIDE = 'R' The vector v in the representation of H. V is not used if TAU = 0. INCV (input) INTEGER The increment between elements of v. INCV <> 0. TAU (input) REAL The value tau in the representation of H. C (input/output) REAL array, dimension (LDC,N) On entry, the m by n matrix C. On exit, C is overwritten by the matrix H * C if SIDE = 'L', or C * H if SIDE = 'R'. LDC (input) INTEGER The leading dimension of the array C. LDC >= max(1,M). WORK (workspace) REAL array, dimension (N) if SIDE = 'L' or (M) if SIDE = 'R' ===================================================================== Parameter adjustments Function Body */ /* Table of constant values */ static real c_b4 = 1.f; static real c_b5 = 0.f; static integer c__1 = 1; /* System generated locals */ integer c_dim1, c_offset; real r__1; /* Local variables */ extern /* Subroutine */ int sger_(integer *, integer *, real *, real *, integer *, real *, integer *, real *, integer *); extern logical lsame_(char *, char *); extern /* Subroutine */ int sgemv_(char *, integer *, integer *, real *, real *, integer *, real *, integer *, real *, real *, integer *);#define V(I) v[(I)-1]#define WORK(I) work[(I)-1]#define C(I,J) c[(I)-1 + ((J)-1)* ( *ldc)] if (lsame_(side, "L")) {/* Form H * C */ if (*tau != 0.f) {/* w := C' * v */ sgemv_("Transpose", m, n, &c_b4, &C(1,1), ldc, &V(1), incv, & c_b5, &WORK(1), &c__1);/* C := C - v * w' */ r__1 = -(doublereal)(*tau); sger_(m, n, &r__1, &V(1), incv, &WORK(1), &c__1, &C(1,1), ldc); } } else {/* Form C * H */ if (*tau != 0.f) {/* w := C * v */ sgemv_("No transpose", m, n, &c_b4, &C(1,1), ldc, &V(1), incv, &c_b5, &WORK(1), &c__1);/* C := C - w * v' */ r__1 = -(doublereal)(*tau); sger_(m, n, &r__1, &WORK(1), &c__1, &V(1), incv, &C(1,1), ldc); } } return 0;/* End of SLARF */} /* slarf_ */
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