nce

api_attr

declarative programming (static graph)

paddle.fluid.layers.nce(input, label, num_total_classes, sample_weight=None, param_attr=None, bias_attr=None, num_neg_samples=None, name=None, sampler='uniform', custom_dist=None, seed=0, is_sparse=False)[source]

Compute and return the noise-contrastive estimation training loss. See Noise-contrastive estimation: A new estimation principle for unnormalized statistical models. By default this operator uses a uniform distribution for sampling.

Parameters
  • input (Variable) – Input variable, 2-D tensor with shape [batch_size, dim], and data type is float32 or float64.

  • label (Variable) – Input label, 2-D tensor with shape [batch_size, num_true_class], and data type is int64.

  • num_total_classes (int) – Total number of classes in all samples.

  • sample_weight (Variable|None) – A Variable of shape [batch_size, 1] storing a weight for each sample. The default weight for each sample is 1.0.

  • param_attr (ParamAttr|None) – To specify the weight parameter attribute. Default: None, which means the default weight parameter property is used. See usage for details in ParamAttr .

  • bias_attr (ParamAttr|None) – To specify the bias parameter attribute. Default: None, which means the default bias parameter property is used. See usage for details in ParamAttr .

  • num_neg_samples (int) – The number of negative classes. The default value is 10.

  • name (str|None) – For detailed information, please refer to Name . Usually name is no need to set and None by default.

  • sampler (str, optional) – The sampler used to sample class from negative classes. It can be ‘uniform’, ‘log_uniform’ or ‘custom_dist’. default: ‘uniform’.

  • custom_dist (nd.array|None) – A numpy ndarray with size=num_total_classes. It is used when sampler is set to ‘custom_dist’. custom_dist[i] is the probability of i-th class to be sampled. default: None.

  • seed (int, optional) – The seed used in sampler. Default 0, means no random seed.

  • is_sparse (bool, optional) – The flag indicating whether to use sparse update, the weight@GRAD and bias@GRAD will be changed to SelectedRows. Default False.

Returns

The output nce loss.

Return type

Variable

Examples

import paddle.fluid as fluid
import numpy as np

window_size = 5
words = []
for i in xrange(window_size):
    words.append(fluid.data(
        name='word_{0}'.format(i), shape=[-1, 1], dtype='int64'))

dict_size = 10000
label_word = int(window_size / 2) + 1

embs = []
for i in xrange(window_size):
    if i == label_word:
        continue

    emb = fluid.layers.embedding(input=words[i], size=[dict_size, 32],
                       param_attr='embed', is_sparse=True)
    embs.append(emb)

embs = fluid.layers.concat(input=embs, axis=1)
loss = fluid.layers.nce(input=embs, label=words[label_word],
          num_total_classes=dict_size, param_attr='nce.w_0',
          bias_attr='nce.b_0')

 #or use custom distribution
 dist = np.array([0.05,0.5,0.1,0.3,0.05])
 loss = fluid.layers.nce(input=embs, label=words[label_word],
           num_total_classes=5, param_attr='nce.w_1',
           bias_attr='nce.b_1',
           num_neg_samples=3,
           sampler="custom_dist",
           custom_dist=dist)