#include "clapack.h"
#include "f2cP.h"

/* Table of constant values */

static integer c__1 = 1;

/* Subroutine */ int dtpcon_(const char *norm, const char *uplo, const char *diag, integer *n, 
	double *ap, double *rcond, double *work, integer *iwork, 
	integer *info)
{
    /* System generated locals */
    integer i__1;
    double d__1;

    /* Local variables */
    integer ix, kase, kase1;
    double scale;
    integer isave[3];
    double anorm;
    bool upper;
    double xnorm;
    double ainvnm;
    bool onenrm;
    char normin[1];
    double smlnum;
    bool nounit;


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

/*     Modified to call DLACN2 in place of DLACON, 5 Feb 03, SJH. */

/*     .. Scalar Arguments .. */
/*     .. */
/*     .. Array Arguments .. */
/*     .. */

/*  Purpose */
/*  ======= */

/*  DTPCON estimates the reciprocal of the condition number of a packed */
/*  triangular matrix A, in either the 1-norm or the infinity-norm. */

/*  The norm of A is computed and an estimate is obtained for */
/*  norm(inv(A)), then 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. */

/*  UPLO    (input) CHARACTER*1 */
/*          = 'U':  A is upper triangular; */
/*          = 'L':  A is lower triangular. */

/*  DIAG    (input) CHARACTER*1 */
/*          = 'N':  A is non-unit triangular; */
/*          = 'U':  A is unit triangular. */

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

/*  AP      (input) DOUBLE PRECISION array, dimension (N*(N+1)/2) */
/*          The upper or lower triangular matrix A, packed columnwise in */
/*          a linear array.  The j-th column of A is stored in the array */
/*          AP as follows: */
/*          if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; */
/*          if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n. */
/*          If DIAG = 'U', the diagonal elements of A are not referenced */
/*          and are assumed to be 1. */

/*  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 */

/*  ===================================================================== */

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. Local Arrays .. */
/*     .. */
/*     .. External Functions .. */
/*     .. */
/*     .. External Subroutines .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Executable Statements .. */

/*     Test the input parameters. */

    /* Parameter adjustments */
    --iwork;
    --work;
    --ap;

    /* Function Body */
    *info = 0;
    upper = lsame_(uplo, "U");
    onenrm = *(unsigned char *)norm == '1' || lsame_(norm, "O");
    nounit = lsame_(diag, "N");

    if (! onenrm && ! lsame_(norm, "I")) {
	*info = -1;
    } else if (! upper && ! lsame_(uplo, "L")) {
	*info = -2;
    } else if (! nounit && ! lsame_(diag, "U")) {
	*info = -3;
    } else if (*n < 0) {
	*info = -4;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("DTPCON", &i__1);
	return 0;
    }

/*     Quick return if possible */

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

    *rcond = 0.;
    smlnum = dlamch_("Safe minimum") * (double) std::max(1_integer,*n);

/*     Compute the norm of the triangular matrix A. */

    anorm = dlantp_(norm, uplo, diag, n, &ap[1], &work[1]);

/*     Continue only if ANORM > 0. */

    if (anorm > 0.) {

/*        Estimate the norm of the inverse of A. */

	ainvnm = 0.;
	*(unsigned char *)normin = 'N';
	if (onenrm) {
	    kase1 = 1;
	} else {
	    kase1 = 2;
	}
	kase = 0;
L10:
	dlacn2_(n, &work[*n + 1], &work[1], &iwork[1], &ainvnm, &kase, isave);
	if (kase != 0) {
	    if (kase == kase1) {

/*              Multiply by inv(A). */

		dlatps_(uplo, "No transpose", diag, normin, n, &ap[1], &work[
			1], &scale, &work[(*n << 1) + 1], info);
	    } else {

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

		dlatps_(uplo, "Transpose", diag, normin, n, &ap[1], &work[1], 
			&scale, &work[(*n << 1) + 1], info);
	    }
	    *(unsigned char *)normin = 'Y';

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

	    if (scale != 1.) {
		ix = idamax_(n, &work[1], &c__1);
		xnorm = (d__1 = work[ix], abs(d__1));
		if (scale < xnorm * 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. / anorm / ainvnm;
	}
    }

L20:
    return 0;

/*     End of DTPCON */

} /* dtpcon_ */
