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Python

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import paddle
from paddle import nn
class SARLoss(nn.Layer):
def __init__(self, **kwargs):
super(SARLoss, self).__init__()
ignore_index = kwargs.get("ignore_index", 92) # 6626
self.loss_func = paddle.nn.loss.CrossEntropyLoss(
reduction="mean", ignore_index=ignore_index
)
def forward(self, predicts, batch):
predict = predicts[
:, :-1, :
] # ignore last index of outputs to be in same seq_len with targets
label = batch[1].astype("int64")[
:, 1:
] # ignore first index of target in loss calculation
batch_size, num_steps, num_classes = (
predict.shape[0],
predict.shape[1],
predict.shape[2],
)
assert (
len(label.shape) == len(list(predict.shape)) - 1
), "The target's shape and inputs's shape is [N, d] and [N, num_steps]"
inputs = paddle.reshape(predict, [-1, num_classes])
targets = paddle.reshape(label, [-1])
loss = self.loss_func(inputs, targets)
return {"loss": loss}