gomu/ext/permutations/permutations.cpp

/**
 * This file is part of Gomu.
 *
 *  Copyright 2016 by Jean Fromentin <jean.fromentin@math.cnrs.fr>
 *
 * Gomu is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Gomu is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Gomu. If not, see <http://www.gnu.org/licenses/>. 
 */


#include "permutations.hpp"


PermutationEnumerator<CoxeterA>::PermutationEnumerator(uint64 r):n(r),sigma(r){
}

void
PermutationEnumerator<CoxeterA>::reset(){
  sigma=Permutation<CoxeterA>(n);
}

const Permutation<CoxeterA>&
PermutationEnumerator<CoxeterA>::get() const{
  return sigma;
}

bool
PermutationEnumerator<CoxeterA>::next(){
  for(int first=n-1;first>0;--first){
    if(sigma.win[first]<sigma.win[first+1]){
      int j=n;
      while(sigma.win[j]<sigma.win[first]) --j;
      swap(sigma.win[j],sigma.win[first]);
      int i=first+1;
      j=n;
      while(i<j) swap(sigma.win[i++],sigma.win[j--]);
      return true;
    }
  }
  return false;
}

PermutationEnumerator<CoxeterB>::PermutationEnumerator(uint64 r):PermutationEnumerator<CoxeterA>(r),sigmaB(r),sign(0){
}

void
PermutationEnumerator<CoxeterB>::reset(){
  PermutationEnumerator<CoxeterA>::reset();
  sigmaB=Permutation<CoxeterB>(n);
  sign=0;
}

const Permutation<CoxeterB>&
PermutationEnumerator<CoxeterB>::get() const{
  return sigmaB;
}

bool
PermutationEnumerator<CoxeterB>::next(){
  ++sign;
  if(sign==(1<<n)){
    sign=0;
    if(not PermutationEnumerator<CoxeterA>::next()) return false;
    sigmaB.m128=sigma.m128;
  }
  else{
    uint64 mask=(1<<(n-1));
    for(uint64 i=1;i<=n;++i){
      sigmaB.win[i]=(mask&sign)?-sigma.win[i]:sigma.win[i];
      mask>>=1;
    }
  }
  return true;
};

PermutationEnumerator<CoxeterD>::PermutationEnumerator(uint64 r):PermutationEnumerator<CoxeterA>(r),sigmaD(r),sign(0){
}

void
PermutationEnumerator<CoxeterD>::reset(){
  PermutationEnumerator<CoxeterA>::reset();
  sigmaD=Permutation<CoxeterD>(n);
  sign=0;
}

const Permutation<CoxeterD>&
PermutationEnumerator<CoxeterD>::get() const{
  return sigmaD;
}

bool
PermutationEnumerator<CoxeterD>::next(){
  ++sign;
  if(sign==(1<<n)){
    sign=0;
    if(not PermutationEnumerator<CoxeterA>::next()) return false;
    sigmaD.m128=sigma.m128;
  }
  else{
    if(__builtin_popcountll(sign)%2==0){
      uint64 mask=1;
      for(uint64 i=1;i<=n;++i){
	sigmaD.win[i]=(mask&sign)?-sigma.win[i]:sigma.win[i];
	mask<<=1;
      }
    }
    else return next();
  }
  return true;
};



int
PermutationEnumerator<CoxeterA>::cmp(const PermutationEnumerator<CoxeterA>& E) const{
  if(n==E.n) return 0;
  if(n<E.n) return 1;
  return -1;
}

 int
PermutationEnumerator<CoxeterB>::cmp(const PermutationEnumerator<CoxeterB>& E) const{
  if(n==E.n) return 0;
  if(n<E.n) return 1;
  return -1;
}

int
PermutationEnumerator<CoxeterD>::cmp(const PermutationEnumerator<CoxeterD>& E) const{
  if(n==E.n) return 0;
  if(n<E.n) return 1;
  return -1;
}