//
//  CRF++ -- Yet Another CRF toolkit
//
//  $Id: lbfgs.h 1588 2007-02-12 09:03:39Z taku $;
//
//  Copyright(C) 2005-2007 Taku Kudo <taku@chasen.org>
//
#ifndef CRFPP_LBFGS_H__
#define CRFPP_LBFGS_H__

#include <vector>
#include <iostream>

namespace CRFPP {

  class LBFGS {
  private:
    class Mcsrch;
    int iflag_, iscn, nfev, iycn, point, npt, iter, info, ispt, isyt, iypt, maxfev;
    double stp, stp1;
    std::vector <double> diag_;
    std::vector <double> w_;
    Mcsrch *mcsrch_;

    void lbfgs_optimize(int size,
                        int msize,
                        double *x,
                        double f,
                        const double *g,
                        double *diag,
                        double *w, bool orthant, double C, int *iflag);

  public:
    explicit LBFGS(): iflag_(0), iscn(0), nfev(0), iycn(0),
                      point(0), npt(0), iter(0), info(0),
                      ispt(0), isyt(0), iypt(0), maxfev(0),
                      stp(0.0), stp1(0.0), mcsrch_(0) {}
    virtual ~LBFGS() { clear(); }

    void clear();

    int optimize(size_t size, double *x, double f, double *g, bool orthant, double C) {
      static const int msize = 5;
      if (w_.empty()) {
        iflag_ = 0;
        w_.resize(size * (2 * msize + 1) + 2 * msize);
        diag_.resize(size);
      } else if (diag_.size() != size) {
        std::cerr << "size of array is different" << std::endl;
        return -1;
      }

      lbfgs_optimize(static_cast<int>(size),
                      msize, x, f, g, &diag_[0], &w_[0], orthant, C, &iflag_);

      if (iflag_ < 0) {
        std::cerr << "routine stops with unexpected error" << std::endl;
        return -1;
      }

      if (iflag_ == 0) {
        clear();
        return 0;   // terminate
      }

      return 1;   // evaluate next f and g
    }
  };
}

#endif