#include "blaswrap.h"
#include "f2c.h"

/* Subroutine */ int dgbcon_(char *norm, integer *n, integer *kl, integer *ku,
	 doublereal *ab, integer *ldab, integer *ipiv, doublereal *anorm, 
	doublereal *rcond, doublereal *work, integer *iwork, integer *info)
{
/*  -- LAPACK routine (version 3.0) --   
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   
       Courant Institute, Argonne National Lab, and Rice University   
       September 30, 1994   


    Purpose   
    =======   

    DGBCON estimates the reciprocal of the condition number of a real   
    general band matrix A, in either the 1-norm or the infinity-norm,   
    using the LU factorization computed by DGBTRF.   

    An estimate is obtained for norm(inv(A)), and the reciprocal of the   
    condition number is computed as   
       RCOND = 1 / ( norm(A) * norm(inv(A)) ).   

    Arguments   
    =========   

    NORM    (input) CHARACTER*1   
            Specifies whether the 1-norm condition number or the   
            infinity-norm condition number is required:   
            = '1' or 'O':  1-norm;   
            = 'I':         Infinity-norm.   

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

    KL      (input) INTEGER   
            The number of subdiagonals within the band of A.  KL >= 0.   

    KU      (input) INTEGER   
            The number of superdiagonals within the band of A.  KU >= 0.   

    AB      (input) DOUBLE PRECISION array, dimension (LDAB,N)   
            Details of the LU factorization of the band matrix A, as   
            computed by DGBTRF.  U is stored as an upper triangular band   
            matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and   
            the multipliers used during the factorization are stored in   
            rows KL+KU+2 to 2*KL+KU+1.   

    LDAB    (input) INTEGER   
            The leading dimension of the array AB.  LDAB >= 2*KL+KU+1.   

    IPIV    (input) INTEGER array, dimension (N)   
            The pivot indices; for 1 <= i <= N, row i of the matrix was   
            interchanged with row IPIV(i).   

    ANORM   (input) DOUBLE PRECISION   
            If NORM = '1' or 'O', the 1-norm of the original matrix A.   
            If NORM = 'I', the infinity-norm of the original matrix A.   

    RCOND   (output) DOUBLE PRECISION   
            The reciprocal of the condition number of the matrix A,   
            computed as RCOND = 1/(norm(A) * norm(inv(A))).   

    WORK    (workspace) DOUBLE PRECISION array, dimension (3*N)   

    IWORK   (workspace) INTEGER array, dimension (N)   

    INFO    (output) INTEGER   
            = 0:  successful exit   
            < 0: if INFO = -i, the i-th argument had an illegal value   

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


       Test the input parameters.   

       Parameter adjustments */
    /* Table of constant values */
    static integer c__1 = 1;
    
    /* System generated locals */
    integer ab_dim1, ab_offset, i__1, i__2, i__3;
    doublereal d__1;
    /* Local variables */
    static integer kase;
    extern doublereal ddot_(integer *, doublereal *, integer *, doublereal *, 
	    integer *);
    static integer kase1, j;
    static doublereal t, scale;
    extern logical lsame_(char *, char *);
    extern /* Subroutine */ int drscl_(integer *, doublereal *, doublereal *, 
	    integer *);
    static logical lnoti;
    extern /* Subroutine */ int daxpy_(integer *, doublereal *, doublereal *, 
	    integer *, doublereal *, integer *);
    static integer kd;
    extern doublereal dlamch_(char *);
    static integer lm, jp, ix;
    extern /* Subroutine */ int dlacon_(integer *, doublereal *, doublereal *,
	     integer *, doublereal *, integer *);
    extern integer idamax_(integer *, doublereal *, integer *);
    extern /* Subroutine */ int dlatbs_(char *, char *, char *, char *, 
	    integer *, integer *, doublereal *, integer *, doublereal *, 
	    doublereal *, doublereal *, integer *), xerbla_(char *, integer *);
    static doublereal ainvnm;
    static logical onenrm;
    static char normin[1];
    static doublereal smlnum;
#define ab_ref(a_1,a_2) ab[(a_2)*ab_dim1 + a_1]


    ab_dim1 = *ldab;
    ab_offset = 1 + ab_dim1 * 1;
    ab -= ab_offset;
    --ipiv;
    --work;
    --iwork;

    /* Function Body */
    *info = 0;
    onenrm = *(unsigned char *)norm == '1' || lsame_(norm, "O");
    if (! onenrm && ! lsame_(norm, "I")) {
	*info = -1;
    } else if (*n < 0) {
	*info = -2;
    } else if (*kl < 0) {
	*info = -3;
    } else if (*ku < 0) {
	*info = -4;
    } else if (*ldab < (*kl << 1) + *ku + 1) {
	*info = -6;
    } else if (*anorm < 0.) {
	*info = -8;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DGBCON", &i__1);
	return 0;
    }

/*     Quick return if possible */

    *rcond = 0.;
    if (*n == 0) {
	*rcond = 1.;
	return 0;
    } else if (*anorm == 0.) {
	return 0;
    }

    smlnum = dlamch_("Safe minimum");

/*     Estimate the norm of inv(A). */

    ainvnm = 0.;
    *(unsigned char *)normin = 'N';
    if (onenrm) {
	kase1 = 1;
    } else {
	kase1 = 2;
    }
    kd = *kl + *ku + 1;
    lnoti = *kl > 0;
    kase = 0;
L10:
    dlacon_(n, &work[*n + 1], &work[1], &iwork[1], &ainvnm, &kase);
    if (kase != 0) {
	if (kase == kase1) {

/*           Multiply by inv(L). */

	    if (lnoti) {
		i__1 = *n - 1;
		for (j = 1; j <= i__1; ++j) {
/* Computing MIN */
		    i__2 = *kl, i__3 = *n - j;
		    lm = min(i__2,i__3);
		    jp = ipiv[j];
		    t = work[jp];
		    if (jp != j) {
			work[jp] = work[j];
			work[j] = t;
		    }
		    d__1 = -t;
		    daxpy_(&lm, &d__1, &ab_ref(kd + 1, j), &c__1, &work[j + 1]
			    , &c__1);
/* L20: */
		}
	    }

/*           Multiply by inv(U). */

	    i__1 = *kl + *ku;
	    dlatbs_("Upper", "No transpose", "Non-unit", normin, n, &i__1, &
		    ab[ab_offset], ldab, &work[1], &scale, &work[(*n << 1) + 
		    1], info);
	} else {

/*           Multiply by inv(U'). */

	    i__1 = *kl + *ku;
	    dlatbs_("Upper", "Transpose", "Non-unit", normin, n, &i__1, &ab[
		    ab_offset], ldab, &work[1], &scale, &work[(*n << 1) + 1], 
		    info);

/*           Multiply by inv(L'). */

	    if (lnoti) {
		for (j = *n - 1; j >= 1; --j) {
/* Computing MIN */
		    i__1 = *kl, i__2 = *n - j;
		    lm = min(i__1,i__2);
		    work[j] -= ddot_(&lm, &ab_ref(kd + 1, j), &c__1, &work[j 
			    + 1], &c__1);
		    jp = ipiv[j];
		    if (jp != j) {
			t = work[jp];
			work[jp] = work[j];
			work[j] = t;
		    }
/* L30: */
		}
	    }
	}

/*        Divide X by 1/SCALE if doing so will not cause overflow. */

	*(unsigned char *)normin = 'Y';
	if (scale != 1.) {
	    ix = idamax_(n, &work[1], &c__1);
	    if (scale < (d__1 = work[ix], abs(d__1)) * smlnum || scale == 0.) 
		    {
		goto L40;
	    }
	    drscl_(n, &scale, &work[1], &c__1);
	}
	goto L10;
    }

/*     Compute the estimate of the reciprocal condition number. */

    if (ainvnm != 0.) {
	*rcond = 1. / ainvnm / *anorm;
    }

L40:
    return 0;

/*     End of DGBCON */

} /* dgbcon_ */

#undef ab_ref


