zlarz.c

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/* zlarz.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 doublecomplex c_b1 = {1.,0.};
static integer c__1 = 1;

/* Subroutine */ int zlarz_(char *side, integer *m, integer *n, integer *l, 
        doublecomplex *v, integer *incv, doublecomplex *tau, doublecomplex *
        c__, integer *ldc, doublecomplex *work)
{
    /* System generated locals */
    integer c_dim1, c_offset;
    doublecomplex z__1;

    /* Local variables */
    extern logical lsame_(char *, char *);
    extern /* Subroutine */ int zgerc_(integer *, integer *, doublecomplex *, 
            doublecomplex *, integer *, doublecomplex *, integer *, 
            doublecomplex *, integer *), zgemv_(char *, integer *, integer *, 
            doublecomplex *, doublecomplex *, integer *, doublecomplex *, 
            integer *, doublecomplex *, doublecomplex *, integer *), 
            zgeru_(integer *, integer *, doublecomplex *, doublecomplex *, 
            integer *, doublecomplex *, integer *, doublecomplex *, integer *)
            , zcopy_(integer *, doublecomplex *, integer *, doublecomplex *, 
            integer *), zaxpy_(integer *, doublecomplex *, doublecomplex *, 
            integer *, doublecomplex *, integer *), zlacgv_(integer *, 
            doublecomplex *, integer *);


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

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

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

/*  ZLARZ 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 ZTZRZF. */

/*  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*16 array, dimension (1+(L-1)*abs(INCV)) */
/*          The vector v in the representation of H as returned by */
/*          ZTZRZF. V is not used if TAU = 0. */

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

/*  TAU     (input) COMPLEX*16 */
/*          The value tau in the representation of H. */

/*  C       (input/output) COMPLEX*16 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*16 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. || tau->i != 0.) {

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

            zcopy_(n, &c__[c_offset], ldc, &work[1], &c__1);
            zlacgv_(n, &work[1], &c__1);

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

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

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

            z__1.r = -tau->r, z__1.i = -tau->i;
            zaxpy_(n, &z__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 )' ) */

            z__1.r = -tau->r, z__1.i = -tau->i;
            zgeru_(l, n, &z__1, &v[1], incv, &work[1], &c__1, &c__[*m - *l + 
                    1 + c_dim1], ldc);
        }

    } else {

/*        Form  C * H */

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

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

            zcopy_(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 ) */

            zgemv_("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 ) */

            z__1.r = -tau->r, z__1.i = -tau->i;
            zaxpy_(m, &z__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 )' */

            z__1.r = -tau->r, z__1.i = -tau->i;
            zgerc_(m, l, &z__1, &work[1], &c__1, &v[1], incv, &c__[(*n - *l + 
                    1) * c_dim1 + 1], ldc);

        }

    }

    return 0;

/*     End of ZLARZ */

} /* zlarz_ */