Combinatorics.h

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//# Smooth.h: smooth vectors and arrays 
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//# $Id$
 
#ifndef SCIMATH_COMBINATORICS_H
#define SCIMATH_COMBINATORICS_H
 
 
//# Includes
#include <casacore/casa/aips.h>
#include <casacore/casa/Arrays/Vector.h>
 
#include <mutex>
 
namespace casacore { //# NAMESPACE CASACORE - BEGIN
 
// <summary>
// Combinatorics related functions.
// </summary>
 
// <use visibility=export>
 
//# <author>Dave Mehringer</author>
// <reviewed reviewer="" date="yyyy/mm/dd" tests="" demos="">
// </reviewed>
 
// <prerequisite>
//   <li> <linkto class="Vector">Vector</linkto>
//   <li> <linkto class="Array">Array</linkto>
// </prerequisite>
 
// <etymology>
// self-explanatory
// </etymology>
 
// <synopsis>
// Various factorial and combinatorical functions.
// </synopsis>
 
// <motivation>
// Binomial coefficients needed for Images/ImageProfileFitter
// </motivation>
 
class Combinatorics {
  
  public:
 
  // Get n!
  static uInt factorial(const uInt n)
  {
    fillCache(n);
    return _factorialCache[n];
  }
  
  // "n choose k" = n!/(k!(n-k)!)
  // Exception is thrown if k > n.
  static uInt choose(const uInt n, const uInt k);
 
  private:
  static void fillCache(const uInt n);
 
  static Vector<uInt> _factorialCache;
  static volatile uInt _factorialCacheSize; //# volatile for double checked lock
  static std::mutex theirMutex;
};
} //# NAMESPACE CASACORE - END
 
#endif