node.h

//
//  CRF++ -- Yet Another CRF toolkit
//
//  $Id: node.h 1595 2007-02-24 10:18:32Z taku $;
//
//  Copyright(C) 2005-2007 Taku Kudo <taku@chasen.org>
//
#ifndef CRFPP_NODE_H_
#define CRFPP_NODE_H_

#include <vector>
#include <cmath>
#include "path.h"
#include "common.h"

#define LOG2               0.69314718055
#define MINUS_LOG_EPSILON  50

namespace CRFPP {
// log(exp(x) + exp(y));
//    this can be used recursivly
// e.g., log(exp(log(exp(x) + exp(y))) + exp(z)) =
// log(exp (x) + exp(y) + exp(z))
inline double logsumexp(double x, double y, bool flg) {
  if (flg) return y;  // init mode
  const double vmin = std::min(x, y);
  const double vmax = std::max(x, y);
  if (vmax > vmin + MINUS_LOG_EPSILON) {
    return vmax;
  } else {
    return vmax + std::log(std::exp(vmin - vmax) + 1.0);
  }
}

struct Path;

struct Node {
  unsigned int         x;
  unsigned short int   y;
  double               alpha;
  double               beta;
  double               cost;
  double               bestCost;
  Node                *prev;
  const int           *fvector;
  std::vector<Path *>  lpath;
  std::vector<Path *>  rpath;

  void calcAlpha();
  void calcBeta();
  void calcExpectation(double *expected, double, size_t) const;

  void clear() {
    x = y = 0;
    alpha = beta = cost = 0.0;
    prev = 0;
    fvector = 0;
    lpath.clear();
    rpath.clear();
  }

  void shrink() {
    std::vector<Path *>(lpath).swap(lpath);
    std::vector<Path *>(rpath).swap(rpath);
  }

  Node() : x(0), y(0), alpha(0.0), beta(0.0),
           cost(0.0), bestCost(0.0), prev(0), fvector(0) {}
};
}
#endif