text: /* dtpcon.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"
  #include "blaswrap.h"
  
  /* Table of constant values */
  
  static integer c__1 = 1;
  
  /* Subroutine */ int dtpcon_(char *norm, char *uplo, char *diag, integer *n, 
  	doublereal *ap, doublereal *rcond, doublereal *work, integer *iwork, 
  	integer *info)
  {
      /* System generated locals */
      integer i__1;
      doublereal d__1;
  
      /* Local variables */
      integer ix, kase, kase1;
      doublereal scale;
      extern logical lsame_(char *, char *);
      integer isave[3];
      extern /* Subroutine */ int drscl_(integer *, doublereal *, doublereal *, 
  	    integer *);
      doublereal anorm;
      logical upper;
      doublereal xnorm;
      extern /* Subroutine */ int dlacn2_(integer *, doublereal *, doublereal *, 
  	     integer *, doublereal *, integer *, integer *);
      extern doublereal dlamch_(char *);
      extern integer idamax_(integer *, doublereal *, integer *);
      extern /* Subroutine */ int xerbla_(char *, integer *);
      extern doublereal dlantp_(char *, char *, char *, integer *, doublereal *, 
  	     doublereal *);
      doublereal ainvnm;
      extern /* Subroutine */ int dlatps_(char *, char *, char *, char *, 
  	    integer *, doublereal *, doublereal *, doublereal *, doublereal *, 
  	     integer *);
      logical onenrm;
      char normin[1];
      doublereal smlnum;
      logical nounit;
  
  
  /*  -- LAPACK routine (version 3.2) -- */
  /*     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") * (doublereal) max(1,*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_ */
  