#include "blaswrap.h"
/* zpbt02.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 doublecomplex c_b1 = {1.,0.};
static integer c__1 = 1;

/* Subroutine */ int zpbt02_(char *uplo, integer *n, integer *kd, integer *
	nrhs, doublecomplex *a, integer *lda, doublecomplex *x, integer *ldx, 
	doublecomplex *b, integer *ldb, doublereal *rwork, doublereal *resid)
{
    /* System generated locals */
    integer a_dim1, a_offset, b_dim1, b_offset, x_dim1, x_offset, i__1;
    doublereal d__1, d__2;
    doublecomplex z__1;

    /* Local variables */
    static integer j;
    static doublereal eps, anorm, bnorm;
    extern /* Subroutine */ int zhbmv_(char *, integer *, integer *, 
	    doublecomplex *, doublecomplex *, integer *, doublecomplex *, 
	    integer *, doublecomplex *, doublecomplex *, integer *);
    static doublereal xnorm;
    extern doublereal dlamch_(char *), zlanhb_(char *, char *, 
	    integer *, integer *, doublecomplex *, integer *, doublereal *), dzasum_(integer *, doublecomplex *, integer *);


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


    Purpose   
    =======   

    ZPBT02 computes the residual for a solution of a Hermitian banded   
    system of equations  A*x = b:   
       RESID = norm( B - A*X ) / ( norm(A) * norm(X) * EPS)   
    where EPS is the machine precision.   

    Arguments   
    =========   

    UPLO    (input) CHARACTER*1   
            Specifies whether the upper or lower triangular part of the   
            Hermitian matrix A is stored:   
            = 'U':  Upper triangular   
            = 'L':  Lower triangular   

    N       (input) INTEGER   
            The number of rows and columns of the matrix A.  N >= 0.   

    KD      (input) INTEGER   
            The number of super-diagonals of the matrix A if UPLO = 'U',   
            or the number of sub-diagonals if UPLO = 'L'.  KD >= 0.   

    A       (input) COMPLEX*16 array, dimension (LDA,N)   
            The original Hermitian band matrix A.  If UPLO = 'U', the   
            upper triangular part of A is stored as a band matrix; if   
            UPLO = 'L', the lower triangular part of A is stored.  The   
            columns of the appropriate triangle are stored in the columns   
            of A and the diagonals of the triangle are stored in the rows   
            of A.  See ZPBTRF for further details.   

    LDA     (input) INTEGER.   
            The leading dimension of the array A.  LDA >= max(1,KD+1).   

    X       (input) COMPLEX*16 array, dimension (LDX,NRHS)   
            The computed solution vectors for the system of linear   
            equations.   

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

    B       (input/output) COMPLEX*16 array, dimension (LDB,NRHS)   
            On entry, the right hand side vectors for the system of   
            linear equations.   
            On exit, B is overwritten with the difference B - A*X.   

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

    RWORK   (workspace) DOUBLE PRECISION array, dimension (N)   

    RESID   (output) DOUBLE PRECISION   
            The maximum over the number of right hand sides of   
            norm(B - A*X) / ( norm(A) * norm(X) * EPS ).   

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


       Quick exit if N = 0 or NRHS = 0.   

       Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    a -= a_offset;
    x_dim1 = *ldx;
    x_offset = 1 + x_dim1;
    x -= x_offset;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1;
    b -= b_offset;
    --rwork;

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

/*     Exit with RESID = 1/EPS if ANORM = 0. */

    eps = dlamch_("Epsilon");
    anorm = zlanhb_("1", uplo, n, kd, &a[a_offset], lda, &rwork[1]);
    if (anorm <= 0.) {
	*resid = 1. / eps;
	return 0;
    }

/*     Compute  B - A*X */

    i__1 = *nrhs;
    for (j = 1; j <= i__1; ++j) {
	z__1.r = -1., z__1.i = -0.;
	zhbmv_(uplo, n, kd, &z__1, &a[a_offset], lda, &x[j * x_dim1 + 1], &
		c__1, &c_b1, &b[j * b_dim1 + 1], &c__1);
/* L10: */
    }

/*     Compute the maximum over the number of right hand sides of   
            norm( B - A*X ) / ( norm(A) * norm(X) * EPS ) */

    *resid = 0.;
    i__1 = *nrhs;
    for (j = 1; j <= i__1; ++j) {
	bnorm = dzasum_(n, &b[j * b_dim1 + 1], &c__1);
	xnorm = dzasum_(n, &x[j * x_dim1 + 1], &c__1);
	if (xnorm <= 0.) {
	    *resid = 1. / eps;
	} else {
/* Computing MAX */
	    d__1 = *resid, d__2 = bnorm / anorm / xnorm / eps;
	    *resid = max(d__1,d__2);
	}
/* L20: */
    }

    return 0;

/*     End of ZPBT02 */

} /* zpbt02_ */