#!/usr/bin/env python
# -*- coding: utf-8 -*-
 
# Copyright 2016 Timothy Dozat
# 
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# 
#     http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.





import tensorflow as tf

from nparser.neural.optimizers.base_optimizer import BaseOptimizer

#***************************************************************
class SGDOptimizer(BaseOptimizer):
  """ """
  
  #=============================================================
  def _apply_dense(self, cache):
    """ """
    
    g_t = cache['g_t']
    cache['s_t'] = self.learning_rate * g_t
    return cache
  
  #=============================================================
  def _apply_sparse(self, cache):
    """ """
    
    g_t, idxs = cache['g_t'], cache['idxs']
    idxs, idxs_ = tf.unique(idxs)
    g_t_ = tf.unsorted_segment_sum(g_t, idxs_, tf.size(idxs))
    
    cache['g_t'] = g_t_
    cache['idxs'] = idxs
    cache['s_t'] = self.learning_rate * g_t_
    
    return cache
  
