/* -- translated by f2c (version 20100827).
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"
/* Table of constant values */
static doublereal c_b4 = 1.;
static doublereal c_b5 = 0.;
static integer c__1 = 1;
/* > \brief \b DLARF applies an elementary reflector to a general rectangular matrix.
=========== DOCUMENTATION ===========
Online html documentation available at
http://www.netlib.org/lapack/explore-html/
> \htmlonly
> Download DLARF + dependencies
>
> [TGZ]
>
> [ZIP]
>
> [TXT]
> \endhtmlonly
Definition:
===========
SUBROUTINE DLARF( SIDE, M, N, V, INCV, TAU, C, LDC, WORK )
CHARACTER SIDE
INTEGER INCV, LDC, M, N
DOUBLE PRECISION TAU
DOUBLE PRECISION C( LDC, * ), V( * ), WORK( * )
> \par Purpose:
=============
>
> \verbatim
>
> DLARF 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**T
>
> where tau is a real scalar and v is a real vector.
>
> If tau = 0, then H is taken to be the unit matrix.
> \endverbatim
Arguments:
==========
> \param[in] SIDE
> \verbatim
> SIDE is CHARACTER*1
> = 'L': form H * C
> = 'R': form C * H
> \endverbatim
>
> \param[in] M
> \verbatim
> M is INTEGER
> The number of rows of the matrix C.
> \endverbatim
>
> \param[in] N
> \verbatim
> N is INTEGER
> The number of columns of the matrix C.
> \endverbatim
>
> \param[in] V
> \verbatim
> V is DOUBLE PRECISION 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.
> \endverbatim
>
> \param[in] INCV
> \verbatim
> INCV is INTEGER
> The increment between elements of v. INCV <> 0.
> \endverbatim
>
> \param[in] TAU
> \verbatim
> TAU is DOUBLE PRECISION
> The value tau in the representation of H.
> \endverbatim
>
> \param[in,out] C
> \verbatim
> C is 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'.
> \endverbatim
>
> \param[in] LDC
> \verbatim
> LDC is INTEGER
> The leading dimension of the array C. LDC >= max(1,M).
> \endverbatim
>
> \param[out] WORK
> \verbatim
> WORK is DOUBLE PRECISION array, dimension
> (N) if SIDE = 'L'
> or (M) if SIDE = 'R'
> \endverbatim
Authors:
========
> \author Univ. of Tennessee
> \author Univ. of California Berkeley
> \author Univ. of Colorado Denver
> \author NAG Ltd.
> \date September 2012
> \ingroup doubleOTHERauxiliary
=====================================================================
Subroutine */ int igraphdlarf_(char *side, integer *m, integer *n, 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 */
integer i__;
logical applyleft;
extern /* Subroutine */ int igraphdger_(integer *, integer *, doublereal *,
doublereal *, integer *, doublereal *, integer *, doublereal *,
integer *);
extern logical igraphlsame_(char *, char *);
extern /* Subroutine */ int igraphdgemv_(char *, integer *, integer *,
doublereal *, doublereal *, integer *, doublereal *, integer *,
doublereal *, doublereal *, integer *);
integer lastc, lastv;
extern integer igraphiladlc_(integer *, integer *, doublereal *, integer *),
igraphiladlr_(integer *, integer *, doublereal *, integer *);
/* -- LAPACK auxiliary routine (version 3.4.2) --
-- LAPACK is a software package provided by Univ. of Tennessee, --
-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
September 2012
=====================================================================
Parameter adjustments */
--v;
c_dim1 = *ldc;
c_offset = 1 + c_dim1;
c__ -= c_offset;
--work;
/* Function Body */
applyleft = igraphlsame_(side, "L");
lastv = 0;
lastc = 0;
if (*tau != 0.) {
/* Set up variables for scanning V. LASTV begins pointing to the end
of V. */
if (applyleft) {
lastv = *m;
} else {
lastv = *n;
}
if (*incv > 0) {
i__ = (lastv - 1) * *incv + 1;
} else {
i__ = 1;
}
/* Look for the last non-zero row in V. */
while(lastv > 0 && v[i__] == 0.) {
--lastv;
i__ -= *incv;
}
if (applyleft) {
/* Scan for the last non-zero column in C(1:lastv,:). */
lastc = igraphiladlc_(&lastv, n, &c__[c_offset], ldc);
} else {
/* Scan for the last non-zero row in C(:,1:lastv). */
lastc = igraphiladlr_(m, &lastv, &c__[c_offset], ldc);
}
}
/* Note that lastc.eq.0 renders the BLAS operations null; no special
case is needed at this level. */
if (applyleft) {
/* Form H * C */
if (lastv > 0) {
/* w(1:lastc,1) := C(1:lastv,1:lastc)**T * v(1:lastv,1) */
igraphdgemv_("Transpose", &lastv, &lastc, &c_b4, &c__[c_offset], ldc, &
v[1], incv, &c_b5, &work[1], &c__1);
/* C(1:lastv,1:lastc) := C(...) - v(1:lastv,1) * w(1:lastc,1)**T */
d__1 = -(*tau);
igraphdger_(&lastv, &lastc, &d__1, &v[1], incv, &work[1], &c__1, &c__[
c_offset], ldc);
}
} else {
/* Form C * H */
if (lastv > 0) {
/* w(1:lastc,1) := C(1:lastc,1:lastv) * v(1:lastv,1) */
igraphdgemv_("No transpose", &lastc, &lastv, &c_b4, &c__[c_offset], ldc,
&v[1], incv, &c_b5, &work[1], &c__1);
/* C(1:lastc,1:lastv) := C(...) - w(1:lastc,1) * v(1:lastv,1)**T */
d__1 = -(*tau);
igraphdger_(&lastc, &lastv, &d__1, &work[1], &c__1, &v[1], incv, &c__[
c_offset], ldc);
}
}
return 0;
/* End of DLARF */
} /* igraphdlarf_ */