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

/* Subroutine */ int dpocon_(char *uplo, integer *n, doublereal *a, integer *
	lda, 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   
       March 31, 1993   


    Purpose   
    =======   

    DPOCON estimates the reciprocal of the condition number (in the   
    1-norm) of a real symmetric positive definite matrix using the   
    Cholesky factorization A = U**T*U or A = L*L**T computed by DPOTRF.   

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

    Arguments   
    =========   

    UPLO    (input) CHARACTER*1   
            = 'U':  Upper triangle of A is stored;   
            = 'L':  Lower triangle of A is stored.   

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

    A       (input) DOUBLE PRECISION array, dimension (LDA,N)   
            The triangular factor U or L from the Cholesky factorization   
            A = U**T*U or A = L*L**T, as computed by DPOTRF.   

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

    ANORM   (input) DOUBLE PRECISION   
            The 1-norm (or infinity-norm) of the symmetric matrix A.   

    RCOND   (output) DOUBLE PRECISION   
            The reciprocal of the condition number of the matrix A,   
            computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an   
            estimate of the 1-norm of inv(A) computed in this routine.   

    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 a_dim1, a_offset, i__1;
    doublereal d__1;
    /* Local variables */
    static integer kase;
    static doublereal scale;
    extern logical lsame_(char *, char *);
    extern /* Subroutine */ int drscl_(integer *, doublereal *, doublereal *, 
	    integer *);
    static logical upper;
    extern doublereal dlamch_(char *);
    extern /* Subroutine */ int dlacon_(integer *, doublereal *, doublereal *,
	     integer *, doublereal *, integer *);
    static integer ix;
    static doublereal scalel;
    extern integer idamax_(integer *, doublereal *, integer *);
    static doublereal scaleu;
    extern /* Subroutine */ int xerbla_(char *, integer *);
    static doublereal ainvnm;
    extern /* Subroutine */ int dlatrs_(char *, char *, char *, char *, 
	    integer *, doublereal *, integer *, doublereal *, doublereal *, 
	    doublereal *, integer *);
    static char normin[1];
    static doublereal smlnum;


    a_dim1 = *lda;
    a_offset = 1 + a_dim1 * 1;
    a -= a_offset;
    --work;
    --iwork;

    /* Function Body */
    *info = 0;
    upper = lsame_(uplo, "U");
    if (! upper && ! lsame_(uplo, "L")) {
	*info = -1;
    } else if (*n < 0) {
	*info = -2;
    } else if (*lda < max(1,*n)) {
	*info = -4;
    } else if (*anorm < 0.) {
	*info = -5;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DPOCON", &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 1-norm of inv(A). */

    kase = 0;
    *(unsigned char *)normin = 'N';
L10:
    dlacon_(n, &work[*n + 1], &work[1], &iwork[1], &ainvnm, &kase);
    if (kase != 0) {
	if (upper) {

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

	    dlatrs_("Upper", "Transpose", "Non-unit", normin, n, &a[a_offset],
		     lda, &work[1], &scalel, &work[(*n << 1) + 1], info);
	    *(unsigned char *)normin = 'Y';

/*           Multiply by inv(U). */

	    dlatrs_("Upper", "No transpose", "Non-unit", normin, n, &a[
		    a_offset], lda, &work[1], &scaleu, &work[(*n << 1) + 1], 
		    info);
	} else {

/*           Multiply by inv(L). */

	    dlatrs_("Lower", "No transpose", "Non-unit", normin, n, &a[
		    a_offset], lda, &work[1], &scalel, &work[(*n << 1) + 1], 
		    info);
	    *(unsigned char *)normin = 'Y';

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

	    dlatrs_("Lower", "Transpose", "Non-unit", normin, n, &a[a_offset],
		     lda, &work[1], &scaleu, &work[(*n << 1) + 1], info);
	}

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

	scale = scalel * scaleu;
	if (scale != 1.) {
	    ix = idamax_(n, &work[1], &c__1);
	    if (scale < (d__1 = work[ix], abs(d__1)) * smlnum || scale == 0.) 
		    {
		goto L20;
	    }
	    drscl_(n, &scale, &work[1], &c__1);
	}
	goto L10;
    }

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

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

L20:
    return 0;

/*     End of DPOCON */

} /* dpocon_ */

