/* Copyright (c) 1992-2008 The University of Tennessee.  All rights reserved.
 * See file COPYING in this directory for details. */

#ifdef __cplusplus
extern "C" {
#endif

#include "f2c.h"
#include "hypre_lapack.h"

/* Subroutine */ integer dlarf_(const char *side, integer *m, integer *n, doublereal *v,
	 integer *incv, doublereal *tau, doublereal *c__, integer *ldc,
	doublereal *work)
{
/*  -- LAPACK auxiliary routine (version 3.0) --
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
       Courant Institute, Argonne National Lab, and Rice University
       February 29, 1992


    Purpose
    =======

    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'

    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) 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.

    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'

    =====================================================================


       Parameter adjustments */
    /* Table of constant values */
    doublereal c_b4 = 1.;
    doublereal c_b5 = 0.;
    integer c__1 = 1;

    /* System generated locals */
    integer c_dim1, c_offset;
    doublereal d__1;
    /* Local variables */
    extern /* Subroutine */ integer dger_(integer *, integer *, doublereal *,
	    doublereal *, integer *, doublereal *, integer *, doublereal *,
	    integer *);
    extern logical lsame_(const char *,const char *);
    extern /* Subroutine */ integer dgemv_(const char *, integer *, integer *,
	    doublereal *, doublereal *, integer *, doublereal *, integer *,
	    doublereal *, doublereal *, integer *);


    --v;
    c_dim1 = *ldc;
    c_offset = 1 + c_dim1 * 1;
    c__ -= c_offset;
    --work;

    /* Function Body */
    if (lsame_(side, "L")) {

/*        Form  H * C */

	if (*tau != 0.) {

/*           w := C' * v */

	    dgemv_("Transpose", m, n, &c_b4, &c__[c_offset], ldc, &v[1], incv,
		     &c_b5, &work[1], &c__1);

/*           C := C - v * w' */

	    d__1 = -(*tau);
	    dger_(m, n, &d__1, &v[1], incv, &work[1], &c__1, &c__[c_offset],
		    ldc);
	}
    } else {

/*        Form  C * H */

	if (*tau != 0.) {

/*           w := C * v */

	    dgemv_("No transpose", m, n, &c_b4, &c__[c_offset], ldc, &v[1],
		    incv, &c_b5, &work[1], &c__1);

/*           C := C - w * v' */

	    d__1 = -(*tau);
	    dger_(m, n, &d__1, &work[1], &c__1, &v[1], incv, &c__[c_offset],
		    ldc);
	}
    }
    return 0;

/*     End of DLARF */

} /* dlarf_ */

#ifdef __cplusplus
}
#endif
