#include "blaswrap.h"
/* drzt01.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"

/* Table of constant values */

static integer c__8 = 8;
static doublereal c_b6 = 0.;
static doublereal c_b13 = -1.;
static integer c__1 = 1;

doublereal drzt01_(integer *m, integer *n, doublereal *a, doublereal *af, 
	integer *lda, doublereal *tau, doublereal *work, integer *lwork)
{
    /* System generated locals */
    integer a_dim1, a_offset, af_dim1, af_offset, i__1, i__2;
    doublereal ret_val;

    /* Local variables */
    static integer i__, j, info;
    static doublereal norma;
    extern /* Subroutine */ int daxpy_(integer *, doublereal *, doublereal *, 
	    integer *, doublereal *, integer *);
    static doublereal rwork[1];
    extern doublereal dlamch_(char *), dlange_(char *, integer *, 
	    integer *, doublereal *, integer *, doublereal *);
    extern /* Subroutine */ int dlaset_(char *, integer *, integer *, 
	    doublereal *, doublereal *, doublereal *, integer *), 
	    xerbla_(char *, integer *), dormrz_(char *, char *, 
	    integer *, integer *, integer *, integer *, doublereal *, integer 
	    *, doublereal *, doublereal *, integer *, doublereal *, integer *,
	     integer *);


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


    Purpose   
    =======   

    DRZT01 returns   
         || A - R*Q || / ( M * eps * ||A|| )   
    for an upper trapezoidal A that was factored with DTZRZF.   

    Arguments   
    =========   

    M       (input) INTEGER   
            The number of rows of the matrices A and AF.   

    N       (input) INTEGER   
            The number of columns of the matrices A and AF.   

    A       (input) DOUBLE PRECISION array, dimension (LDA,N)   
            The original upper trapezoidal M by N matrix A.   

    AF      (input) DOUBLE PRECISION array, dimension (LDA,N)   
            The output of DTZRZF for input matrix A.   
            The lower triangle is not referenced.   

    LDA     (input) INTEGER   
            The leading dimension of the arrays A and AF.   

    TAU     (input) DOUBLE PRECISION array, dimension (M)   
            Details of the Householder transformations as returned by   
            DTZRZF.   

    WORK    (workspace) DOUBLE PRECISION array, dimension (LWORK)   

    LWORK   (input) INTEGER   
            The length of the array WORK.  LWORK >= m*n + m*nb.   

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


       Parameter adjustments */
    af_dim1 = *lda;
    af_offset = 1 + af_dim1;
    af -= af_offset;
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    --tau;
    --work;

    /* Function Body */
    ret_val = 0.;

    if (*lwork < *m * *n + *m) {
	xerbla_("DRZT01", &c__8);
	return ret_val;
    }

/*     Quick return if possible */

    if (*m <= 0 || *n <= 0) {
	return ret_val;
    }

    norma = dlange_("One-norm", m, n, &a[a_offset], lda, rwork);

/*     Copy upper triangle R */

    dlaset_("Full", m, n, &c_b6, &c_b6, &work[1], m);
    i__1 = *m;
    for (j = 1; j <= i__1; ++j) {
	i__2 = j;
	for (i__ = 1; i__ <= i__2; ++i__) {
	    work[(j - 1) * *m + i__] = af[i__ + j * af_dim1];
/* L10: */
	}
/* L20: */
    }

/*     R = R * P(1) * ... *P(m) */

    i__1 = *n - *m;
    i__2 = *lwork - *m * *n;
    dormrz_("Right", "No tranpose", m, n, m, &i__1, &af[af_offset], lda, &tau[
	    1], &work[1], m, &work[*m * *n + 1], &i__2, &info);

/*     R = R - A */

    i__1 = *n;
    for (i__ = 1; i__ <= i__1; ++i__) {
	daxpy_(m, &c_b13, &a[i__ * a_dim1 + 1], &c__1, &work[(i__ - 1) * *m + 
		1], &c__1);
/* L30: */
    }

    ret_val = dlange_("One-norm", m, n, &work[1], m, rwork);

    ret_val /= dlamch_("Epsilon") * (doublereal) max(*m,*n);
    if (norma != 0.) {
	ret_val /= norma;
    }

    return ret_val;

/*     End of DRZT01 */

} /* drzt01_ */