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tf.sequence_mask

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Returns a mask tensor representing the first N positions of each cell.

If lengths has shape [d_1, d_2, ..., d_n] the resulting tensor mask has dtype dtype and shape [d_1, d_2, ..., d_n, maxlen], with

mask[i_1, i_2, ..., i_n, j] = (j < lengths[i_1, i_2, ..., i_n])

Examples:

tf.sequence_mask([1, 3, 2], 5)  # [[True, False, False, False, False],
                                #  [True, True, True, False, False],
                                #  [True, True, False, False, False]]

tf.sequence_mask([[1, 3],[2,0]])  # [[[True, False, False],
                                  #   [True, True, True]],
                                  #  [[True, True, False],
                                  #   [False, False, False]]]
Args
lengths integer tensor, all its values <= maxlen.
maxlen scalar integer tensor, size of last dimension of returned tensor. Default is the maximum value in lengths.
dtype output type of the resulting tensor.
name name of the op.
Returns
A mask tensor of shape lengths.shape + (maxlen,), cast to specified dtype.
Raises
ValueError if maxlen is not a scalar.

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Licensed under the Creative Commons Attribution License 3.0.
Code samples licensed under the Apache 2.0 License.
https://www.tensorflow.org/versions/r1.15/api_docs/python/tf/sequence_mask