sqrt03.c

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/* sqrt03.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"

/* Common Block Declarations */

struct {
    char srnamt[32];
} srnamc_;

#define srnamc_1 srnamc_

/* Table of constant values */

static real c_b4 = -1e10f;
static integer c__2 = 2;
static real c_b21 = -1.f;
static real c_b22 = 1.f;

/* Subroutine */ int sqrt03_(integer *m, integer *n, integer *k, real *af, 
        real *c__, real *cc, real *q, integer *lda, real *tau, real *work, 
        integer *lwork, real *rwork, real *result)
{
    /* Initialized data */

    static integer iseed[4] = { 1988,1989,1990,1991 };

    /* System generated locals */
    integer af_dim1, af_offset, c_dim1, c_offset, cc_dim1, cc_offset, q_dim1, 
            q_offset, i__1;

    /* Builtin functions */
    /* Subroutine */ int s_copy(char *, char *, ftnlen, ftnlen);

    /* Local variables */
    integer j, mc, nc;
    real eps;
    char side[1];
    integer info, iside;
    extern logical lsame_(char *, char *);
    real resid;
    extern /* Subroutine */ int sgemm_(char *, char *, integer *, integer *, 
            integer *, real *, real *, integer *, real *, integer *, real *, 
            real *, integer *);
    real cnorm;
    char trans[1];
    extern doublereal slamch_(char *), slange_(char *, integer *, 
            integer *, real *, integer *, real *);
    extern /* Subroutine */ int slacpy_(char *, integer *, integer *, real *, 
            integer *, real *, integer *), slaset_(char *, integer *, 
            integer *, real *, real *, real *, integer *);
    integer itrans;
    extern /* Subroutine */ int slarnv_(integer *, integer *, integer *, real 
            *), sorgqr_(integer *, integer *, integer *, real *, integer *, 
            real *, real *, integer *, integer *), sormqr_(char *, char *, 
            integer *, integer *, integer *, real *, integer *, real *, real *
, integer *, real *, integer *, integer *);


/*  -- LAPACK test routine (version 3.1) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/*     November 2006 */

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

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

/*  SQRT03 tests SORMQR, which computes Q*C, Q'*C, C*Q or C*Q'. */

/*  SQRT03 compares the results of a call to SORMQR with the results of */
/*  forming Q explicitly by a call to SORGQR and then performing matrix */
/*  multiplication by a call to SGEMM. */

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

/*  M       (input) INTEGER */
/*          The order of the orthogonal matrix Q.  M >= 0. */

/*  N       (input) INTEGER */
/*          The number of rows or columns of the matrix C; C is m-by-n if */
/*          Q is applied from the left, or n-by-m if Q is applied from */
/*          the right.  N >= 0. */

/*  K       (input) INTEGER */
/*          The number of elementary reflectors whose product defines the */
/*          orthogonal matrix Q.  M >= K >= 0. */

/*  AF      (input) REAL array, dimension (LDA,N) */
/*          Details of the QR factorization of an m-by-n matrix, as */
/*          returnedby SGEQRF. See SGEQRF for further details. */

/*  C       (workspace) REAL array, dimension (LDA,N) */

/*  CC      (workspace) REAL array, dimension (LDA,N) */

/*  Q       (workspace) REAL array, dimension (LDA,M) */

/*  LDA     (input) INTEGER */
/*          The leading dimension of the arrays AF, C, CC, and Q. */

/*  TAU     (input) REAL array, dimension (min(M,N)) */
/*          The scalar factors of the elementary reflectors corresponding */
/*          to the QR factorization in AF. */

/*  WORK    (workspace) REAL array, dimension (LWORK) */

/*  LWORK   (input) INTEGER */
/*          The length of WORK.  LWORK must be at least M, and should be */
/*          M*NB, where NB is the blocksize for this environment. */

/*  RWORK   (workspace) REAL array, dimension (M) */

/*  RESULT  (output) REAL array, dimension (4) */
/*          The test ratios compare two techniques for multiplying a */
/*          random matrix C by an m-by-m orthogonal matrix Q. */
/*          RESULT(1) = norm( Q*C - Q*C )  / ( M * norm(C) * EPS ) */
/*          RESULT(2) = norm( C*Q - C*Q )  / ( M * norm(C) * EPS ) */
/*          RESULT(3) = norm( Q'*C - Q'*C )/ ( M * norm(C) * EPS ) */
/*          RESULT(4) = norm( C*Q' - C*Q' )/ ( M * norm(C) * EPS ) */

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

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. External Functions .. */
/*     .. */
/*     .. External Subroutines .. */
/*     .. */
/*     .. Local Arrays .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Scalars in Common .. */
/*     .. */
/*     .. Common blocks .. */
/*     .. */
/*     .. Data statements .. */
    /* Parameter adjustments */
    q_dim1 = *lda;
    q_offset = 1 + q_dim1;
    q -= q_offset;
    cc_dim1 = *lda;
    cc_offset = 1 + cc_dim1;
    cc -= cc_offset;
    c_dim1 = *lda;
    c_offset = 1 + c_dim1;
    c__ -= c_offset;
    af_dim1 = *lda;
    af_offset = 1 + af_dim1;
    af -= af_offset;
    --tau;
    --work;
    --rwork;
    --result;

    /* Function Body */
/*     .. */
/*     .. Executable Statements .. */

    eps = slamch_("Epsilon");

/*     Copy the first k columns of the factorization to the array Q */

    slaset_("Full", m, m, &c_b4, &c_b4, &q[q_offset], lda);
    i__1 = *m - 1;
    slacpy_("Lower", &i__1, k, &af[af_dim1 + 2], lda, &q[q_dim1 + 2], lda);

/*     Generate the m-by-m matrix Q */

    s_copy(srnamc_1.srnamt, "SORGQR", (ftnlen)32, (ftnlen)6);
    sorgqr_(m, m, k, &q[q_offset], lda, &tau[1], &work[1], lwork, &info);

    for (iside = 1; iside <= 2; ++iside) {
        if (iside == 1) {
            *(unsigned char *)side = 'L';
            mc = *m;
            nc = *n;
        } else {
            *(unsigned char *)side = 'R';
            mc = *n;
            nc = *m;
        }

/*        Generate MC by NC matrix C */

        i__1 = nc;
        for (j = 1; j <= i__1; ++j) {
            slarnv_(&c__2, iseed, &mc, &c__[j * c_dim1 + 1]);
/* L10: */
        }
        cnorm = slange_("1", &mc, &nc, &c__[c_offset], lda, &rwork[1]);
        if (cnorm == 0.f) {
            cnorm = 1.f;
        }

        for (itrans = 1; itrans <= 2; ++itrans) {
            if (itrans == 1) {
                *(unsigned char *)trans = 'N';
            } else {
                *(unsigned char *)trans = 'T';
            }

/*           Copy C */

            slacpy_("Full", &mc, &nc, &c__[c_offset], lda, &cc[cc_offset], 
                    lda);

/*           Apply Q or Q' to C */

            s_copy(srnamc_1.srnamt, "SORMQR", (ftnlen)32, (ftnlen)6);
            sormqr_(side, trans, &mc, &nc, k, &af[af_offset], lda, &tau[1], &
                    cc[cc_offset], lda, &work[1], lwork, &info);

/*           Form explicit product and subtract */

            if (lsame_(side, "L")) {
                sgemm_(trans, "No transpose", &mc, &nc, &mc, &c_b21, &q[
                        q_offset], lda, &c__[c_offset], lda, &c_b22, &cc[
                        cc_offset], lda);
            } else {
                sgemm_("No transpose", trans, &mc, &nc, &nc, &c_b21, &c__[
                        c_offset], lda, &q[q_offset], lda, &c_b22, &cc[
                        cc_offset], lda);
            }

/*           Compute error in the difference */

            resid = slange_("1", &mc, &nc, &cc[cc_offset], lda, &rwork[1]);
            result[(iside - 1 << 1) + itrans] = resid / ((real) max(1,*m) * 
                    cnorm * eps);

/* L20: */
        }
/* L30: */
    }

    return 0;

/*     End of SQRT03 */

} /* sqrt03_ */