dlarzb.c

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/* dlarzb.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_b13 = 1.;
static doublereal c_b23 = -1.;

/* Subroutine */ int dlarzb_(char *side, char *trans, char *direct, char *
        storev, integer *m, integer *n, integer *k, integer *l, doublereal *v, 
         integer *ldv, doublereal *t, integer *ldt, doublereal *c__, integer *
        ldc, doublereal *work, integer *ldwork)
{
    /* System generated locals */
    integer c_dim1, c_offset, t_dim1, t_offset, v_dim1, v_offset, work_dim1, 
            work_offset, i__1, i__2;

    /* Local variables */
    integer i__, j, info;
    extern /* Subroutine */ int dgemm_(char *, char *, integer *, integer *, 
            integer *, doublereal *, doublereal *, integer *, doublereal *, 
            integer *, doublereal *, doublereal *, integer *);
    extern logical lsame_(char *, char *);
    extern /* Subroutine */ int dcopy_(integer *, doublereal *, integer *, 
            doublereal *, integer *), dtrmm_(char *, char *, char *, char *, 
            integer *, integer *, doublereal *, doublereal *, integer *, 
            doublereal *, integer *), xerbla_(
            char *, integer *);
    char transt[1];


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

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

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

/*  DLARZB applies a real block reflector H or its transpose H**T to */
/*  a real distributed M-by-N  C from the left or the right. */

/*  Currently, only STOREV = 'R' and DIRECT = 'B' are supported. */

/*  Arguments */
/*  ========= */

/*  SIDE    (input) CHARACTER*1 */
/*          = 'L': apply H or H' from the Left */
/*          = 'R': apply H or H' from the Right */

/*  TRANS   (input) CHARACTER*1 */
/*          = 'N': apply H (No transpose) */
/*          = 'C': apply H' (Transpose) */

/*  DIRECT  (input) CHARACTER*1 */
/*          Indicates how H is formed from a product of elementary */
/*          reflectors */
/*          = 'F': H = H(1) H(2) . . . H(k) (Forward, not supported yet) */
/*          = 'B': H = H(k) . . . H(2) H(1) (Backward) */

/*  STOREV  (input) CHARACTER*1 */
/*          Indicates how the vectors which define the elementary */
/*          reflectors are stored: */
/*          = 'C': Columnwise                        (not supported yet) */
/*          = 'R': Rowwise */

/*  M       (input) INTEGER */
/*          The number of rows of the matrix C. */

/*  N       (input) INTEGER */
/*          The number of columns of the matrix C. */

/*  K       (input) INTEGER */
/*          The order of the matrix T (= the number of elementary */
/*          reflectors whose product defines the block reflector). */

/*  L       (input) INTEGER */
/*          The number of columns of the matrix V containing the */
/*          meaningful part of the Householder reflectors. */
/*          If SIDE = 'L', M >= L >= 0, if SIDE = 'R', N >= L >= 0. */

/*  V       (input) DOUBLE PRECISION array, dimension (LDV,NV). */
/*          If STOREV = 'C', NV = K; if STOREV = 'R', NV = L. */

/*  LDV     (input) INTEGER */
/*          The leading dimension of the array V. */
/*          If STOREV = 'C', LDV >= L; if STOREV = 'R', LDV >= K. */

/*  T       (input) DOUBLE PRECISION array, dimension (LDT,K) */
/*          The triangular K-by-K matrix T in the representation of the */
/*          block reflector. */

/*  LDT     (input) INTEGER */
/*          The leading dimension of the array T. LDT >= K. */

/*  C       (input/output) DOUBLE PRECISION array, dimension (LDC,N) */
/*          On entry, the M-by-N matrix C. */
/*          On exit, C is overwritten by H*C or H'*C or C*H or C*H'. */

/*  LDC     (input) INTEGER */
/*          The leading dimension of the array C. LDC >= max(1,M). */

/*  WORK    (workspace) DOUBLE PRECISION array, dimension (LDWORK,K) */

/*  LDWORK  (input) INTEGER */
/*          The leading dimension of the array WORK. */
/*          If SIDE = 'L', LDWORK >= max(1,N); */
/*          if SIDE = 'R', LDWORK >= max(1,M). */

/*  Further Details */
/*  =============== */

/*  Based on contributions by */
/*    A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA */

/*  ===================================================================== */

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. External Functions .. */
/*     .. */
/*     .. External Subroutines .. */
/*     .. */
/*     .. Executable Statements .. */

/*     Quick return if possible */

    /* Parameter adjustments */
    v_dim1 = *ldv;
    v_offset = 1 + v_dim1;
    v -= v_offset;
    t_dim1 = *ldt;
    t_offset = 1 + t_dim1;
    t -= t_offset;
    c_dim1 = *ldc;
    c_offset = 1 + c_dim1;
    c__ -= c_offset;
    work_dim1 = *ldwork;
    work_offset = 1 + work_dim1;
    work -= work_offset;

    /* Function Body */
    if (*m <= 0 || *n <= 0) {
        return 0;
    }

/*     Check for currently supported options */

    info = 0;
    if (! lsame_(direct, "B")) {
        info = -3;
    } else if (! lsame_(storev, "R")) {
        info = -4;
    }
    if (info != 0) {
        i__1 = -info;
        xerbla_("DLARZB", &i__1);
        return 0;
    }

    if (lsame_(trans, "N")) {
        *(unsigned char *)transt = 'T';
    } else {
        *(unsigned char *)transt = 'N';
    }

    if (lsame_(side, "L")) {

/*        Form  H * C  or  H' * C */

/*        W( 1:n, 1:k ) = C( 1:k, 1:n )' */

        i__1 = *k;
        for (j = 1; j <= i__1; ++j) {
            dcopy_(n, &c__[j + c_dim1], ldc, &work[j * work_dim1 + 1], &c__1);
/* L10: */
        }

/*        W( 1:n, 1:k ) = W( 1:n, 1:k ) + ... */
/*                        C( m-l+1:m, 1:n )' * V( 1:k, 1:l )' */

        if (*l > 0) {
            dgemm_("Transpose", "Transpose", n, k, l, &c_b13, &c__[*m - *l + 
                    1 + c_dim1], ldc, &v[v_offset], ldv, &c_b13, &work[
                    work_offset], ldwork);
        }

/*        W( 1:n, 1:k ) = W( 1:n, 1:k ) * T'  or  W( 1:m, 1:k ) * T */

        dtrmm_("Right", "Lower", transt, "Non-unit", n, k, &c_b13, &t[
                t_offset], ldt, &work[work_offset], ldwork);

/*        C( 1:k, 1:n ) = C( 1:k, 1:n ) - W( 1:n, 1:k )' */

        i__1 = *n;
        for (j = 1; j <= i__1; ++j) {
            i__2 = *k;
            for (i__ = 1; i__ <= i__2; ++i__) {
                c__[i__ + j * c_dim1] -= work[j + i__ * work_dim1];
/* L20: */
            }
/* L30: */
        }

/*        C( m-l+1:m, 1:n ) = C( m-l+1:m, 1:n ) - ... */
/*                            V( 1:k, 1:l )' * W( 1:n, 1:k )' */

        if (*l > 0) {
            dgemm_("Transpose", "Transpose", l, n, k, &c_b23, &v[v_offset], 
                    ldv, &work[work_offset], ldwork, &c_b13, &c__[*m - *l + 1 
                    + c_dim1], ldc);
        }

    } else if (lsame_(side, "R")) {

/*        Form  C * H  or  C * H' */

/*        W( 1:m, 1:k ) = C( 1:m, 1:k ) */

        i__1 = *k;
        for (j = 1; j <= i__1; ++j) {
            dcopy_(m, &c__[j * c_dim1 + 1], &c__1, &work[j * work_dim1 + 1], &
                    c__1);
/* L40: */
        }

/*        W( 1:m, 1:k ) = W( 1:m, 1:k ) + ... */
/*                        C( 1:m, n-l+1:n ) * V( 1:k, 1:l )' */

        if (*l > 0) {
            dgemm_("No transpose", "Transpose", m, k, l, &c_b13, &c__[(*n - *
                    l + 1) * c_dim1 + 1], ldc, &v[v_offset], ldv, &c_b13, &
                    work[work_offset], ldwork);
        }

/*        W( 1:m, 1:k ) = W( 1:m, 1:k ) * T  or  W( 1:m, 1:k ) * T' */

        dtrmm_("Right", "Lower", trans, "Non-unit", m, k, &c_b13, &t[t_offset]
, ldt, &work[work_offset], ldwork);

/*        C( 1:m, 1:k ) = C( 1:m, 1:k ) - W( 1:m, 1:k ) */

        i__1 = *k;
        for (j = 1; j <= i__1; ++j) {
            i__2 = *m;
            for (i__ = 1; i__ <= i__2; ++i__) {
                c__[i__ + j * c_dim1] -= work[i__ + j * work_dim1];
/* L50: */
            }
/* L60: */
        }

/*        C( 1:m, n-l+1:n ) = C( 1:m, n-l+1:n ) - ... */
/*                            W( 1:m, 1:k ) * V( 1:k, 1:l ) */

        if (*l > 0) {
            dgemm_("No transpose", "No transpose", m, l, k, &c_b23, &work[
                    work_offset], ldwork, &v[v_offset], ldv, &c_b13, &c__[(*n 
                    - *l + 1) * c_dim1 + 1], ldc);
        }

    }

    return 0;

/*     End of DLARZB */

} /* dlarzb_ */