1:  // Author & Copyright : Peter Luschny

   2:  // Created: 2010-01-15

   3:  // License: LGPL version 2.1 or (at your option)

   4:  // Creative Commons Attribution-ShareAlike 3.0

   5:   

   6:  #ifndef PRIMESWING_H_

   7:  #define PRIMESWING_H_

   8:   

   9:  #include "lmp.h"

  10:   

  11:  static const ulong smallOddSwing[] =  {

  12:      1, 1, 1, 3, 3, 15, 5, 35, 35, 315, 63, 693, 231, 3003, 429,

  13:      6435, 6435, 109395, 12155, 230945, 46189, 969969, 88179,

  14:      2028117, 676039, 16900975, 1300075, 35102025, 5014575,

  15:      145422675, 9694845, 300540195, 300540195 };

  16:   

  17:  class PrimeSwing {

  18:  public:

  19:   

  20:      // Computes the factorial of an integer.

  21:      static void Factorial(Xint fact, ulong n);

  22:   

  23:      // Computes the factorial of an integer using threads.

  24:      static void ParallelFactorial(Xint fact, ulong n);

  25:   

  26:      // Computes the double factorial (Swing algo).

  27:      static void DoubleFactorial(Xint fact, ulong n);

  28:   

  29:      // Computes the double factorial (Swing algo).

  30:      static void ParallelDoubleFactorial(Xint fact, ulong n);

  31:   

  32:  private:

  33:   

  34:      static const unsigned int THRESHOLD = 20;

  35:      static const ulong SOSLEN = 33;

  36:   

  37:      static long GetIndexOf(ulong* p, ulong val, slong low, slong high)

  38:      {

  39:          slong lim = high;

  40:          while (low < high)

  41:          {

  42:              slong mid = low + (high - low) / 2;

  43:              if (p[mid] < val) { low = mid + 1; }

  44:              else { high = mid; }

  45:          }

  46:          if (low >= lim) { return low; }

  47:          if (p[low] == val) { low++; }

  48:   

  49:          return low;

  50:      }

  51:  };

  52:   

  53:  #endif // PRIMESWING_H_