LaInverse.cxx

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// @(#)root/minuit2:$Id$
// Authors: M. Winkler, F. James, L. Moneta, A. Zsenei   2003-2005
 
/**********************************************************************
 *                                                                    *
 * Copyright (c) 2005 LCG ROOT Math team,  CERN/PH-SFT                *
 *                                                                    *
 **********************************************************************/
 
#include "Minuit2/LaInverse.h"
#include "Minuit2/LASymMatrix.h"
 
namespace ROOT {
 
   namespace Minuit2 {
 
 
int mnvert(LASymMatrix& t);
 
// symmetric matrix (positive definite only)
 
int Invert(LASymMatrix& t) {
   // function for inversion of symmetric matrices using  mnvert function
   // (from Fortran Minuit)
 
   int ifail = 0;
 
   if(t.size() == 1) {
      double tmp = t.Data()[0];
      if(!(tmp > 0.)) ifail = 1;
      else t.Data()[0] = 1./tmp;
   } else {
      ifail = mnvert(t);
   }
 
   return ifail;
}
 
 
   }  // namespace Minuit2
 
}  // namespace ROOT