arow.cpp

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// Jubatus: Online machine learning framework for distributed environment
// Copyright (C) 2011 Preferred Networks and Nippon Telegraph and Telephone Corporation.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License version 2.1 as published by the Free Software Foundation.
//
// This library 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

#include "arow.hpp"

#include <algorithm>
#include <cmath>
#include <string>

#include "jubatus/util/concurrent/lock.h"
#include "classifier_util.hpp"
#include "../common/exception.hpp"

using std::string;

namespace jubatus {
namespace core {
namespace classifier {

arow::arow(storage_ptr storage)
    : linear_classifier(storage) {
}

arow::arow(
    const classifier_config& config,
    storage_ptr storage)
    : linear_classifier(storage),
      config_(config) {

  if (!(0.f < config.regularization_weight)) {
    throw JUBATUS_EXCEPTION(
        common::invalid_parameter("0.0 < regularization_weight"));
  }
}

void arow::train(const common::sfv_t& sfv, const string& label) {
  check_touchable(label);

  string incorrect_label;
  float variance = 0.f;
  float margin = -calc_margin_and_variance(sfv, label, incorrect_label,
                                           variance);
  if (margin >= 1.f) {
    storage_->register_label(label);
    return;
  }

  float beta = 1.f / (variance + 1.f / config_.regularization_weight);
  float alpha = (1.f - margin) * beta;  // max(0, 1 - margin) = 1 - margin
  update(sfv, alpha, beta, label, incorrect_label);
}

void arow::update(
    const common::sfv_t& sfv,
    float alpha,
    float beta,
    const std::string& pos_label,
    const std::string& neg_label) {
  util::concurrent::scoped_lock lk(storage_->get_lock());
  for (common::sfv_t::const_iterator it = sfv.begin(); it != sfv.end(); ++it) {
    const string& feature = it->first;
    float val = it->second;
    storage::feature_val2_t ret;
    storage_->get2_nolock(feature, ret);

    storage::val2_t pos_val(0.f, 1.f);
    storage::val2_t neg_val(0.f, 1.f);
    ClassifierUtil::get_two(ret, pos_label, neg_label, pos_val, neg_val);

    storage_->set2_nolock(
        feature,
        pos_label,
        storage::val2_t(
            pos_val.v1 + alpha * pos_val.v2 * val,
            pos_val.v2 - beta * pos_val.v2 * pos_val.v2 * val * val));
    if (neg_label != "") {
      storage_->set2_nolock(
          feature,
          neg_label,
          storage::val2_t(
              neg_val.v1 - alpha * neg_val.v2 * val,
              neg_val.v2 - beta * neg_val.v2 * neg_val.v2 * val * val));
    }
  }
  touch(pos_label);
}

string arow::name() const {
  return string("arow");
}

}  // namespace classifier
}  // namespace core
}  // namespace jubatus