#include "blaswrap.h"
/* stbt06.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"

/* Subroutine */ int stbt06_(real *rcond, real *rcondc, char *uplo, char *
	diag, integer *n, integer *kd, real *ab, integer *ldab, real *work, 
	real *rat)
{
    /* System generated locals */
    integer ab_dim1, ab_offset;
    real r__1, r__2;

    /* Local variables */
    static real eps, rmin, rmax, anorm;
    extern /* Subroutine */ int slabad_(real *, real *);
    extern doublereal slamch_(char *);
    static real bignum;
    extern doublereal slantb_(char *, char *, char *, integer *, integer *, 
	    real *, integer *, real *);
    static real smlnum;


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


    Purpose   
    =======   

    STBT06 computes a test ratio comparing RCOND (the reciprocal   
    condition number of a triangular matrix A) and RCONDC, the estimate   
    computed by STBCON.  Information about the triangular matrix A is   
    used if one estimate is zero and the other is non-zero to decide if   
    underflow in the estimate is justified.   

    Arguments   
    =========   

    RCOND   (input) REAL   
            The estimate of the reciprocal condition number obtained by   
            forming the explicit inverse of the matrix A and computing   
            RCOND = 1/( norm(A) * norm(inv(A)) ).   

    RCONDC  (input) REAL   
            The estimate of the reciprocal condition number computed by   
            STBCON.   

    UPLO    (input) CHARACTER   
            Specifies whether the matrix A is upper or lower triangular.   
            = 'U':  Upper triangular   
            = 'L':  Lower triangular   

    DIAG    (input) CHARACTER   
            Specifies whether or not the matrix A is unit triangular.   
            = 'N':  Non-unit triangular   
            = 'U':  Unit triangular   

    N       (input) INTEGER   
            The order of the matrix A.  N >= 0.   

    KD      (input) INTEGER   
            The number of superdiagonals or subdiagonals of the   
            triangular band matrix A.  KD >= 0.   

    AB      (input) REAL array, dimension (LDAB,N)   
            The upper or lower triangular band matrix A, stored in the   
            first kd+1 rows of the array. The j-th column of A is stored   
            in the j-th column of the array AB as follows:   
            if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j;   
            if UPLO = 'L', AB(1+i-j,j)    = A(i,j) for j<=i<=min(n,j+kd).   

    LDAB    (input) INTEGER   
            The leading dimension of the array AB.  LDAB >= KD+1.   

    WORK    (workspace) REAL array, dimension (N)   

    RAT     (output) REAL   
            The test ratio.  If both RCOND and RCONDC are nonzero,   
               RAT = MAX( RCOND, RCONDC )/MIN( RCOND, RCONDC ) - 1.   
            If RAT = 0, the two estimates are exactly the same.   

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


       Parameter adjustments */
    ab_dim1 = *ldab;
    ab_offset = 1 + ab_dim1;
    ab -= ab_offset;
    --work;

    /* Function Body */
    eps = slamch_("Epsilon");
    rmax = dmax(*rcond,*rcondc);
    rmin = dmin(*rcond,*rcondc);

/*     Do the easy cases first. */

    if (rmin < 0.f) {

/*        Invalid value for RCOND or RCONDC, return 1/EPS. */

	*rat = 1.f / eps;

    } else if (rmin > 0.f) {

/*        Both estimates are positive, return RMAX/RMIN - 1. */

	*rat = rmax / rmin - 1.f;

    } else if (rmax == 0.f) {

/*        Both estimates zero. */

	*rat = 0.f;

    } else {

/*        One estimate is zero, the other is non-zero.  If the matrix is   
          ill-conditioned, return the nonzero estimate multiplied by   
          1/EPS; if the matrix is badly scaled, return the nonzero   
          estimate multiplied by BIGNUM/TMAX, where TMAX is the maximum   
          element in absolute value in A. */

	smlnum = slamch_("Safe minimum");
	bignum = 1.f / smlnum;
	slabad_(&smlnum, &bignum);
	anorm = slantb_("M", uplo, diag, n, kd, &ab[ab_offset], ldab, &work[1] );

/* Computing MIN */
	r__1 = bignum / dmax(1.f,anorm), r__2 = 1.f / eps;
	*rat = rmax * dmin(r__1,r__2);
    }

    return 0;

/*     End of STBT06 */

} /* stbt06_ */