/* dlarz.f -- translated by f2c (version 20061008).
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
*/
#include "f2c.h"
#include "blaswrap.h"
/* Table of constant values */
static integer c__1 = 1;
static doublereal c_b5 = 1.;
/* Subroutine */ int dlarz_(char *side, integer *m, integer *n, integer *l,
doublereal *v, integer *incv, doublereal *tau, doublereal *c__,
integer *ldc, doublereal *work)
{
/* System generated locals */
integer c_dim1, c_offset;
doublereal d__1;
/* Local variables */
extern /* Subroutine */ int dger_(integer *, integer *, doublereal *,
doublereal *, integer *, doublereal *, integer *, doublereal *,
integer *);
extern logical lsame_(char *, char *);
extern /* Subroutine */ int dgemv_(char *, integer *, integer *,
doublereal *, doublereal *, integer *, doublereal *, integer *,
doublereal *, doublereal *, integer *), dcopy_(integer *,
doublereal *, integer *, doublereal *, integer *), daxpy_(integer
*, doublereal *, doublereal *, integer *, doublereal *, integer *)
;
/* -- LAPACK routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DLARZ 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. */
/* H is a product of k elementary reflectors as returned by DTZRZF. */
/* 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. */
/* L (input) INTEGER */
/* The number of entries of the vector V containing */
/* the meaningful part of the Householder vectors. */
/* If SIDE = 'L', M >= L >= 0, if SIDE = 'R', N >= L >= 0. */
/* V (input) DOUBLE PRECISION array, dimension (1+(L-1)*abs(INCV)) */
/* The vector v in the representation of H as returned by */
/* DTZRZF. V is not used if TAU = 0. */
/* INCV (input) INTEGER */
/* The increment between elements of v. INCV <> 0. */
/* TAU (input) DOUBLE PRECISION */
/* The value tau in the representation of H. */
/* C (input/output) DOUBLE PRECISION 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) DOUBLE PRECISION array, dimension */
/* (N) if SIDE = 'L' */
/* or (M) if SIDE = 'R' */
/* Further Details */
/* =============== */
/* Based on contributions by */
/* A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Parameter adjustments */
--v;
c_dim1 = *ldc;
c_offset = 1 + c_dim1;
c__ -= c_offset;
--work;
/* Function Body */
if (lsame_(side, "L")) {
/* Form H * C */
if (*tau != 0.) {
/* w( 1:n ) = C( 1, 1:n ) */
dcopy_(n, &c__[c_offset], ldc, &work[1], &c__1);
/* w( 1:n ) = w( 1:n ) + C( m-l+1:m, 1:n )' * v( 1:l ) */
dgemv_("Transpose", l, n, &c_b5, &c__[*m - *l + 1 + c_dim1], ldc,
&v[1], incv, &c_b5, &work[1], &c__1);
/* C( 1, 1:n ) = C( 1, 1:n ) - tau * w( 1:n ) */
d__1 = -(*tau);
daxpy_(n, &d__1, &work[1], &c__1, &c__[c_offset], ldc);
/* C( m-l+1:m, 1:n ) = C( m-l+1:m, 1:n ) - ... */
/* tau * v( 1:l ) * w( 1:n )' */
d__1 = -(*tau);
dger_(l, n, &d__1, &v[1], incv, &work[1], &c__1, &c__[*m - *l + 1
+ c_dim1], ldc);
}
} else {
/* Form C * H */
if (*tau != 0.) {
/* w( 1:m ) = C( 1:m, 1 ) */
dcopy_(m, &c__[c_offset], &c__1, &work[1], &c__1);
/* w( 1:m ) = w( 1:m ) + C( 1:m, n-l+1:n, 1:n ) * v( 1:l ) */
dgemv_("No transpose", m, l, &c_b5, &c__[(*n - *l + 1) * c_dim1 +
1], ldc, &v[1], incv, &c_b5, &work[1], &c__1);
/* C( 1:m, 1 ) = C( 1:m, 1 ) - tau * w( 1:m ) */
d__1 = -(*tau);
daxpy_(m, &d__1, &work[1], &c__1, &c__[c_offset], &c__1);
/* C( 1:m, n-l+1:n ) = C( 1:m, n-l+1:n ) - ... */
/* tau * w( 1:m ) * v( 1:l )' */
d__1 = -(*tau);
dger_(m, l, &d__1, &work[1], &c__1, &v[1], incv, &c__[(*n - *l +
1) * c_dim1 + 1], ldc);
}
}
return 0;
/* End of DLARZ */
} /* dlarz_ */
