#include "blaswrap.h"
/* stbt03.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 stbt03_(char *uplo, char *trans, char *diag, integer *n, 
	integer *kd, integer *nrhs, real *ab, integer *ldab, real *scale, 
	real *cnorm, real *tscal, real *x, integer *ldx, real *b, integer *
	ldb, real *work, real *resid)
{
    /* System generated locals */
    integer ab_dim1, ab_offset, b_dim1, b_offset, x_dim1, x_offset, i__1;
    real r__1, r__2, r__3;

    /* Local variables */
    static integer j, ix;
    static real eps, err;
    extern logical lsame_(char *, char *);
    extern /* Subroutine */ int sscal_(integer *, real *, real *, integer *);
    static real xscal;
    extern /* Subroutine */ int stbmv_(char *, char *, char *, integer *, 
	    integer *, real *, integer *, real *, integer *), scopy_(integer *, real *, integer *, real *, integer *);
    static real tnorm, xnorm;
    extern /* Subroutine */ int saxpy_(integer *, real *, real *, integer *, 
	    real *, integer *), slabad_(real *, real *);
    extern doublereal slamch_(char *);
    static real bignum;
    extern integer isamax_(integer *, real *, integer *);
    static real smlnum;


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


    Purpose   
    =======   

    STBT03 computes the residual for the solution to a scaled triangular   
    system of equations  A*x = s*b  or  A'*x = s*b  when A is a   
    triangular band matrix. Here A' is the transpose of A, s is a scalar,   
    and x and b are N by NRHS matrices.  The test ratio is the maximum   
    over the number of right hand sides of   
       norm(s*b - op(A)*x) / ( norm(op(A)) * norm(x) * EPS ),   
    where op(A) denotes A or A' and EPS is the machine epsilon.   

    Arguments   
    =========   

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

    TRANS   (input) CHARACTER*1   
            Specifies the operation applied to A.   
            = 'N':  A *x = b  (No transpose)   
            = 'T':  A'*x = b  (Transpose)   
            = 'C':  A'*x = b  (Conjugate transpose = Transpose)   

    DIAG    (input) CHARACTER*1   
            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.   

    NRHS    (input) INTEGER   
            The number of right hand sides, i.e., the number of columns   
            of the matrices X and B.  NRHS >= 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.   

    SCALE   (input) REAL   
            The scaling factor s used in solving the triangular system.   

    CNORM   (input) REAL array, dimension (N)   
            The 1-norms of the columns of A, not counting the diagonal.   

    TSCAL   (input) REAL   
            The scaling factor used in computing the 1-norms in CNORM.   
            CNORM actually contains the column norms of TSCAL*A.   

    X       (input) REAL 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) REAL 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).   

    WORK    (workspace) REAL array, dimension (N)   

    RESID   (output) REAL   
            The maximum over the number of right hand sides of   
            norm(op(A)*x - s*b) / ( norm(op(A)) * norm(x) * EPS ).   

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


       Quick exit if N = 0   

       Parameter adjustments */
    ab_dim1 = *ldab;
    ab_offset = 1 + ab_dim1;
    ab -= ab_offset;
    --cnorm;
    x_dim1 = *ldx;
    x_offset = 1 + x_dim1;
    x -= x_offset;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1;
    b -= b_offset;
    --work;

    /* Function Body */
    if (*n <= 0 || *nrhs <= 0) {
	*resid = 0.f;
	return 0;
    }
    eps = slamch_("Epsilon");
    smlnum = slamch_("Safe minimum");
    bignum = 1.f / smlnum;
    slabad_(&smlnum, &bignum);

/*     Compute the norm of the triangular matrix A using the column   
       norms already computed by SLATBS. */

    tnorm = 0.f;
    if (lsame_(diag, "N")) {
	if (lsame_(uplo, "U")) {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
/* Computing MAX */
		r__2 = tnorm, r__3 = *tscal * (r__1 = ab[*kd + 1 + j * 
			ab_dim1], dabs(r__1)) + cnorm[j];
		tnorm = dmax(r__2,r__3);
/* L10: */
	    }
	} else {
	    i__1 = *n;
	    for (j = 1; j <= i__1; ++j) {
/* Computing MAX */
		r__2 = tnorm, r__3 = *tscal * (r__1 = ab[j * ab_dim1 + 1], 
			dabs(r__1)) + cnorm[j];
		tnorm = dmax(r__2,r__3);
/* L20: */
	    }
	}
    } else {
	i__1 = *n;
	for (j = 1; j <= i__1; ++j) {
/* Computing MAX */
	    r__1 = tnorm, r__2 = *tscal + cnorm[j];
	    tnorm = dmax(r__1,r__2);
/* L30: */
	}
    }

/*     Compute the maximum over the number of right hand sides of   
          norm(op(A)*x - s*b) / ( norm(op(A)) * norm(x) * EPS ). */

    *resid = 0.f;
    i__1 = *nrhs;
    for (j = 1; j <= i__1; ++j) {
	scopy_(n, &x[j * x_dim1 + 1], &c__1, &work[1], &c__1);
	ix = isamax_(n, &work[1], &c__1);
/* Computing MAX */
	r__2 = 1.f, r__3 = (r__1 = x[ix + j * x_dim1], dabs(r__1));
	xnorm = dmax(r__2,r__3);
	xscal = 1.f / xnorm / (real) (*kd + 1);
	sscal_(n, &xscal, &work[1], &c__1);
	stbmv_(uplo, trans, diag, n, kd, &ab[ab_offset], ldab, &work[1], &
		c__1);
	r__1 = -(*scale) * xscal;
	saxpy_(n, &r__1, &b[j * b_dim1 + 1], &c__1, &work[1], &c__1);
	ix = isamax_(n, &work[1], &c__1);
	err = *tscal * (r__1 = work[ix], dabs(r__1));
	ix = isamax_(n, &x[j * x_dim1 + 1], &c__1);
	xnorm = (r__1 = x[ix + j * x_dim1], dabs(r__1));
	if (err * smlnum <= xnorm) {
	    if (xnorm > 0.f) {
		err /= xnorm;
	    }
	} else {
	    if (err > 0.f) {
		err = 1.f / eps;
	    }
	}
	if (err * smlnum <= tnorm) {
	    if (tnorm > 0.f) {
		err /= tnorm;
	    }
	} else {
	    if (err > 0.f) {
		err = 1.f / eps;
	    }
	}
	*resid = dmax(*resid,err);
/* L40: */
    }

    return 0;

/*     End of STBT03 */

} /* stbt03_ */