clarz.c

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/* clarz.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 complex c_b1 = {1.f,0.f};
static integer c__1 = 1;

/* Subroutine */ int clarz_(char *side, integer *m, integer *n, integer *l, 
        complex *v, integer *incv, complex *tau, complex *c__, integer *ldc, 
        complex *work)
{
    /* System generated locals */
    integer c_dim1, c_offset;
    complex q__1;

    /* Local variables */
    extern /* Subroutine */ int cgerc_(integer *, integer *, complex *, 
            complex *, integer *, complex *, integer *, complex *, integer *),
             cgemv_(char *, integer *, integer *, complex *, complex *, 
            integer *, complex *, integer *, complex *, complex *, integer *);
    extern logical lsame_(char *, char *);
    extern /* Subroutine */ int cgeru_(integer *, integer *, complex *, 
            complex *, integer *, complex *, integer *, complex *, integer *),
             ccopy_(integer *, complex *, integer *, complex *, integer *), 
            caxpy_(integer *, complex *, complex *, integer *, complex *, 
            integer *), clacgv_(integer *, complex *, integer *);


/*  -- LAPACK routine (version 3.2) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/*     November 2006 */

/*     .. Scalar Arguments .. */
/*     .. */
/*     .. Array Arguments .. */
/*     .. */

/*  Purpose */
/*  ======= */

/*  CLARZ applies a complex elementary reflector H to a complex */
/*  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 complex scalar and v is a complex vector. */

/*  If tau = 0, then H is taken to be the unit matrix. */

/*  To apply H' (the conjugate transpose of H), supply conjg(tau) instead */
/*  tau. */

/*  H is a product of k elementary reflectors as returned by CTZRZF. */

/*  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) COMPLEX array, dimension (1+(L-1)*abs(INCV)) */
/*          The vector v in the representation of H as returned by */
/*          CTZRZF. V is not used if TAU = 0. */

/*  INCV    (input) INTEGER */
/*          The increment between elements of v. INCV <> 0. */

/*  TAU     (input) COMPLEX */
/*          The value tau in the representation of H. */

/*  C       (input/output) COMPLEX 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) COMPLEX 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->r != 0.f || tau->i != 0.f) {

/*           w( 1:n ) = conjg( C( 1, 1:n ) ) */

            ccopy_(n, &c__[c_offset], ldc, &work[1], &c__1);
            clacgv_(n, &work[1], &c__1);

/*           w( 1:n ) = conjg( w( 1:n ) + C( m-l+1:m, 1:n )' * v( 1:l ) ) */

            cgemv_("Conjugate transpose", l, n, &c_b1, &c__[*m - *l + 1 + 
                    c_dim1], ldc, &v[1], incv, &c_b1, &work[1], &c__1);
            clacgv_(n, &work[1], &c__1);

/*           C( 1, 1:n ) = C( 1, 1:n ) - tau * w( 1:n ) */

            q__1.r = -tau->r, q__1.i = -tau->i;
            caxpy_(n, &q__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 ) * conjg( w( 1:n )' ) */

            q__1.r = -tau->r, q__1.i = -tau->i;
            cgeru_(l, n, &q__1, &v[1], incv, &work[1], &c__1, &c__[*m - *l + 
                    1 + c_dim1], ldc);
        }

    } else {

/*        Form  C * H */

        if (tau->r != 0.f || tau->i != 0.f) {

/*           w( 1:m ) = C( 1:m, 1 ) */

            ccopy_(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 ) */

            cgemv_("No transpose", m, l, &c_b1, &c__[(*n - *l + 1) * c_dim1 + 
                    1], ldc, &v[1], incv, &c_b1, &work[1], &c__1);

/*           C( 1:m, 1 ) = C( 1:m, 1 ) - tau * w( 1:m ) */

            q__1.r = -tau->r, q__1.i = -tau->i;
            caxpy_(m, &q__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 )' */

            q__1.r = -tau->r, q__1.i = -tau->i;
            cgerc_(m, l, &q__1, &work[1], &c__1, &v[1], incv, &c__[(*n - *l + 
                    1) * c_dim1 + 1], ldc);

        }

    }

    return 0;

/*     End of CLARZ */

} /* clarz_ */