#include "blaswrap.h"
/* dptt05.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__1 = 1;

/* Subroutine */ int dptt05_(integer *n, integer *nrhs, doublereal *d__, 
	doublereal *e, doublereal *b, integer *ldb, doublereal *x, integer *
	ldx, doublereal *xact, integer *ldxact, doublereal *ferr, doublereal *
	berr, doublereal *reslts)
{
    /* System generated locals */
    integer b_dim1, b_offset, x_dim1, x_offset, xact_dim1, xact_offset, i__1, 
	    i__2;
    doublereal d__1, d__2, d__3, d__4;

    /* Local variables */
    static integer i__, j, k, nz;
    static doublereal eps, tmp, diff, axbi;
    static integer imax;
    static doublereal unfl, ovfl, xnorm;
    extern doublereal dlamch_(char *);
    extern integer idamax_(integer *, doublereal *, integer *);
    static doublereal errbnd;


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


    Purpose   
    =======   

    DPTT05 tests the error bounds from iterative refinement for the   
    computed solution to a system of equations A*X = B, where A is a   
    symmetric tridiagonal matrix of order n.   

    RESLTS(1) = test of the error bound   
              = norm(X - XACT) / ( norm(X) * FERR )   

    A large value is returned if this ratio is not less than one.   

    RESLTS(2) = residual from the iterative refinement routine   
              = the maximum of BERR / ( NZ*EPS + (*) ), where   
                (*) = NZ*UNFL / (min_i (abs(A)*abs(X) +abs(b))_i )   
                and NZ = max. number of nonzeros in any row of A, plus 1   

    Arguments   
    =========   

    N       (input) INTEGER   
            The number of rows of the matrices X, B, and XACT, and the   
            order of the matrix A.  N >= 0.   

    NRHS    (input) INTEGER   
            The number of columns of the matrices X, B, and XACT.   
            NRHS >= 0.   

    D       (input) DOUBLE PRECISION array, dimension (N)   
            The n diagonal elements of the tridiagonal matrix A.   

    E       (input) DOUBLE PRECISION array, dimension (N-1)   
            The (n-1) subdiagonal elements of the tridiagonal matrix A.   

    B       (input) DOUBLE PRECISION array, dimension (LDB,NRHS)   
            The right hand side vectors for the system of linear   
            equations.   

    LDB     (input) INTEGER   
            The leading dimension of the array B.  LDB >= max(1,N).   

    X       (input) DOUBLE PRECISION array, dimension (LDX,NRHS)   
            The computed solution vectors.  Each vector is stored as a   
            column of the matrix X.   

    LDX     (input) INTEGER   
            The leading dimension of the array X.  LDX >= max(1,N).   

    XACT    (input) DOUBLE PRECISION array, dimension (LDX,NRHS)   
            The exact solution vectors.  Each vector is stored as a   
            column of the matrix XACT.   

    LDXACT  (input) INTEGER   
            The leading dimension of the array XACT.  LDXACT >= max(1,N).   

    FERR    (input) DOUBLE PRECISION array, dimension (NRHS)   
            The estimated forward error bounds for each solution vector   
            X.  If XTRUE is the true solution, FERR bounds the magnitude   
            of the largest entry in (X - XTRUE) divided by the magnitude   
            of the largest entry in X.   

    BERR    (input) DOUBLE PRECISION array, dimension (NRHS)   
            The componentwise relative backward error of each solution   
            vector (i.e., the smallest relative change in any entry of A   
            or B that makes X an exact solution).   

    RESLTS  (output) DOUBLE PRECISION array, dimension (2)   
            The maximum over the NRHS solution vectors of the ratios:   
            RESLTS(1) = norm(X - XACT) / ( norm(X) * FERR )   
            RESLTS(2) = BERR / ( NZ*EPS + (*) )   

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


       Quick exit if N = 0 or NRHS = 0.   

       Parameter adjustments */
    --d__;
    --e;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1;
    b -= b_offset;
    x_dim1 = *ldx;
    x_offset = 1 + x_dim1;
    x -= x_offset;
    xact_dim1 = *ldxact;
    xact_offset = 1 + xact_dim1;
    xact -= xact_offset;
    --ferr;
    --berr;
    --reslts;

    /* Function Body */
    if (*n <= 0 || *nrhs <= 0) {
	reslts[1] = 0.;
	reslts[2] = 0.;
	return 0;
    }

    eps = dlamch_("Epsilon");
    unfl = dlamch_("Safe minimum");
    ovfl = 1. / unfl;
    nz = 4;

/*     Test 1:  Compute the maximum of   
          norm(X - XACT) / ( norm(X) * FERR )   
       over all the vectors X and XACT using the infinity-norm. */

    errbnd = 0.;
    i__1 = *nrhs;
    for (j = 1; j <= i__1; ++j) {
	imax = idamax_(n, &x[j * x_dim1 + 1], &c__1);
/* Computing MAX */
	d__2 = (d__1 = x[imax + j * x_dim1], abs(d__1));
	xnorm = max(d__2,unfl);
	diff = 0.;
	i__2 = *n;
	for (i__ = 1; i__ <= i__2; ++i__) {
/* Computing MAX */
	    d__2 = diff, d__3 = (d__1 = x[i__ + j * x_dim1] - xact[i__ + j * 
		    xact_dim1], abs(d__1));
	    diff = max(d__2,d__3);
/* L10: */
	}

	if (xnorm > 1.) {
	    goto L20;
	} else if (diff <= ovfl * xnorm) {
	    goto L20;
	} else {
	    errbnd = 1. / eps;
	    goto L30;
	}

L20:
	if (diff / xnorm <= ferr[j]) {
/* Computing MAX */
	    d__1 = errbnd, d__2 = diff / xnorm / ferr[j];
	    errbnd = max(d__1,d__2);
	} else {
	    errbnd = 1. / eps;
	}
L30:
	;
    }
    reslts[1] = errbnd;

/*     Test 2:  Compute the maximum of BERR / ( NZ*EPS + (*) ), where   
       (*) = NZ*UNFL / (min_i (abs(A)*abs(X) +abs(b))_i ) */

    i__1 = *nrhs;
    for (k = 1; k <= i__1; ++k) {
	if (*n == 1) {
	    axbi = (d__1 = b[k * b_dim1 + 1], abs(d__1)) + (d__2 = d__[1] * x[
		    k * x_dim1 + 1], abs(d__2));
	} else {
	    axbi = (d__1 = b[k * b_dim1 + 1], abs(d__1)) + (d__2 = d__[1] * x[
		    k * x_dim1 + 1], abs(d__2)) + (d__3 = e[1] * x[k * x_dim1 
		    + 2], abs(d__3));
	    i__2 = *n - 1;
	    for (i__ = 2; i__ <= i__2; ++i__) {
		tmp = (d__1 = b[i__ + k * b_dim1], abs(d__1)) + (d__2 = e[i__ 
			- 1] * x[i__ - 1 + k * x_dim1], abs(d__2)) + (d__3 = 
			d__[i__] * x[i__ + k * x_dim1], abs(d__3)) + (d__4 = 
			e[i__] * x[i__ + 1 + k * x_dim1], abs(d__4));
		axbi = min(axbi,tmp);
/* L40: */
	    }
	    tmp = (d__1 = b[*n + k * b_dim1], abs(d__1)) + (d__2 = e[*n - 1] *
		     x[*n - 1 + k * x_dim1], abs(d__2)) + (d__3 = d__[*n] * x[
		    *n + k * x_dim1], abs(d__3));
	    axbi = min(axbi,tmp);
	}
/* Computing MAX */
	d__1 = axbi, d__2 = nz * unfl;
	tmp = berr[k] / (nz * eps + nz * unfl / max(d__1,d__2));
	if (k == 1) {
	    reslts[2] = tmp;
	} else {
	    reslts[2] = max(reslts[2],tmp);
	}
/* L50: */
    }

    return 0;

/*     End of DPTT05 */

} /* dptt05_ */