1NF.cpp

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// MIT License
//
// Copyright (c) 2023 Ian Parberry
//
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// of this software and associated documentation files (the "Software"), to
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#include "Defines.h"
#include "TernaryGrayCode.h"
 
#include "1NF.h"
 
 
C1NF::C1NF(): CSortingNetwork(){
  delete m_pGrayCode;
  m_pGrayCode = new CTernaryGrayCode;
 
  //first layer is the identity matching
 
  const size_t n = evenfloor(m_nWidth); 
 
  for(size_t i=0; i<n; i++)
    m_nComparator[0][i] = i ^ 1;
} //constructor
 
 
void C1NF::Initialize(){ 
  m_pGrayCode->Initialize(); //initialize the Gray code to all zeros.
  InitValues(1, m_nDepth - 1); //initialize the network values to all zeros.
  m_nZeros = m_nWidth; //all zeros
} //initialize
 
 
bool C1NF::StillSorts(const size_t delta){
  const size_t nTarget = m_nValue[1][delta]? m_nZeros: m_nZeros - 1;
  return FlipInput(delta, 1, m_nDepth - 1) == nTarget;
} //StillSorts
 
 
bool C1NF::EvenSorts(){ 
  size_t i = 0;  //index of bit to flip
  bool bSorts = true; //assume it sorts until we find otherwise
 
  while(bSorts && i < m_nWidth){ //bail if it doesn't sort, or we've tried all binary inputs
    i = m_pGrayCode->Next(); //next bit to flip in Gray code order
    bSorts = bSorts && (i >= m_nWidth || StillSorts(i)); //check whether it still sorts when this bit is flipped
  } //while
 
  return bSorts;
} //EvenSorts
 
 
bool C1NF::Sorts(){ 
  //first handle the case where n is even, and the case where n is odd
  //and fails to sort an input that ends with a zero
  Initialize(); //set all channels to zero
  if(!EvenSorts())return false;  //test inputs ending in zero
 
  //if odd number of inputs, check input that end with a one 
  if(odd(m_nWidth)){   
    Initialize(); //set all channels to zero
 
    for(int j=0; j<m_nDepth; j++) //set all values on last channel to one
      m_nValue[j][m_nWidth - 1] = 1;
 
    m_nZeros = m_nWidth - 1; //correct the count of zeros
 
    if(!EvenSorts())return false; //test inputs ending with one
  } //if
 
  return true; //Oh, we made it this far? Then I must be a sorting network. Hurray!
} //sorts