mindspore.nn.Perplexity
- class mindspore.nn.Perplexity(ignore_label=None)[source]
Computes perplexity. Perplexity is a measurement about how well a probability distribution or a model predicts a sample. A low perplexity indicates the model can predict the sample well. The function is shown as follows:
\[PP(W)=P(w_{1}w_{2}...w_{N})^{-\frac{1}{N}}=\sqrt[N]{\frac{1}{P(w_{1}w_{2}...w_{N})}}\]Where \(w\) represents words in corpus.
- Parameters
ignore_label (Union[int, None]) – Index of an invalid label to be ignored when counting. If set to None, it will include all entries. Default: None.
- Supported Platforms:
Ascend
GPU
CPU
Examples
>>> import numpy as np >>> from mindspore import nn, Tensor >>> x = Tensor(np.array([[0.2, 0.5], [0.3, 0.1], [0.9, 0.6]])) >>> y = Tensor(np.array([1, 0, 1])) >>> metric = nn.Perplexity(ignore_label=None) >>> metric.clear() >>> metric.update(x, y) >>> perplexity = metric.eval() >>> print(perplexity) 2.231443166940565
- eval()[source]
Returns the current evaluation result.
- Returns
numpy.float64. The computed result.
- Raises
RuntimeError – If the sample size is 0.
- update(*inputs)[source]
Updates the internal evaluation result preds and labels.
- Parameters
inputs – Input preds and labels. preds and labels are a Tensor, list or numpy.ndarray. preds is the predicted values, labels is the labels of the data. The shape of preds and labels are both \((N, C)\).
- Raises
ValueError – If the number of the inputs is not 2.
RuntimeError – If preds and labels have different lengths.
RuntimeError – If label shape is not equal to pred shape.