F2wCycleBasedLFSR.java

/*
 * Class:        F2wCycleBasedLFSR
 * Description:  point set based upon a linear feedback shift register
                 sequence
 * Environment:  Java
 * Software:     SSJ 
 * Copyright (C) 2001  Pierre L'Ecuyer and Universite de Montreal
 * Organization: DIRO, Universite de Montreal
 * @author       
 * @since
 *
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */
package umontreal.ssj.hups;
 
import cern.colt.list.*;
import umontreal.ssj.util.PrintfFormat;

public class F2wCycleBasedLFSR extends CycleBasedPointSetBase2 {
 
   private F2wStructure param;

   public F2wCycleBasedLFSR(int w, int r, int modQ, int step, int nbcoeff, int coeff[], int nocoeff[])
   {
      param = new F2wStructure(w, r, modQ, step, nbcoeff, coeff, nocoeff);
      init();
   }

   public F2wCycleBasedLFSR(String filename, int no) {
      param = new F2wStructure(filename, no);
      init();
   }
 
   private void init() {
      param.initParamLFSR();
      normFactor = param.normFactor;
      EpsilonHalf = param.EpsilonHalf;
      numBits = param.numBits;
      fillCyclesLFSR();
   }
 
   public String toString() {
      String s = "F2wCycleBasedLFSR:" + PrintfFormat.NEWLINE;
      return s + param.toString();
   }
 
   private void fillCyclesLFSR() {
      int n = 1 << param.getLog2N();
      IntArrayList c; // Array used to store the current cycle.
      int currentState; // The state currently visited.
      int i;
      boolean stateVisited[] = new boolean[n];
 
      // Indicates which states have been visited so far.
      for (i = 0; i < n; i++)
         stateVisited[i] = false;
      int startState = 0; // First state of the cycle currently considered.
      numPoints = 0;
      while (startState < n) {
         stateVisited[startState] = true;
         c = new IntArrayList();
         param.state = startState;
         param.initF2wLFSR();
         c.add(param.output);
         param.F2wLFSR();
         // Warning: watch for overflow !!!
         while (param.state != startState) {
            stateVisited[param.state] = true;
            c.add(param.output);
            param.F2wLFSR();
         }
         addCycle(c);
         for (i = startState + 1; i < n; i++)
            if (stateVisited[i] == false)
               break;
         startState = i;
      }
   }
}