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88 lines
2.9 KiB
88 lines
2.9 KiB
from typing import Callable, List, Sequence, Tuple, TypeVar, Union, cast
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from ..config import registry
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from ..model import Model
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from ..types import ArrayXd, Padded, Ragged
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InT = TypeVar("InT", bound=Union[ArrayXd, Sequence[ArrayXd], Ragged, Padded])
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@registry.layers("Dropout.v1")
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def Dropout(rate: float = 0.0) -> Model[InT, InT]:
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"""Help prevent overfitting by adding a random distortion to the input data
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during training. Specifically, cells of the input are zeroed with
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probability determined by the `rate` argument.
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"""
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return Model("dropout", forward, attrs={"dropout_rate": rate, "is_enabled": True})
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def forward(model: Model[InT, InT], X: InT, is_train: bool) -> Tuple[InT, Callable]:
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rate = model.attrs["dropout_rate"]
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is_enabled = model.attrs["is_enabled"] and is_train
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if rate == 0 or not is_enabled:
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return X, lambda dY: dY
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elif isinstance(X, Ragged):
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data_r, backprop = _dropout_ragged(model, X, is_train)
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return cast(InT, data_r), backprop
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elif isinstance(X, Padded):
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data_p, backprop = _dropout_padded(model, X, is_train)
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return cast(InT, data_p), backprop
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elif isinstance(X, Sequence):
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data_l, backprop = _dropout_lists(model, X, is_train)
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return cast(InT, data_l), backprop
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else:
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data_a, backprop = _dropout_array(model, cast(ArrayXd, X), is_train)
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return cast(InT, data_a), backprop
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def _dropout_array(
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model: Model[InT, InT], X: ArrayXd, is_train: bool
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) -> Tuple[ArrayXd, Callable]:
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rate = model.attrs["dropout_rate"]
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mask = model.ops.get_dropout_mask(X.shape, rate)
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def backprop(dY: ArrayXd) -> ArrayXd:
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return dY * mask
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return cast(ArrayXd, X * mask), backprop
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def _dropout_padded(
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model: Model[InT, InT], Xp: Padded, is_train: bool
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) -> Tuple[Padded, Callable]:
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X = Xp.data
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mask = model.ops.get_dropout_mask(X.shape, model.attrs["dropout_rate"])
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Y = X * mask
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def backprop(dYp: Padded) -> Padded:
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return Padded(dYp.data * mask, dYp.size_at_t, dYp.lengths, dYp.indices)
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return Padded(Y, Xp.size_at_t, Xp.lengths, Xp.indices), backprop
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def _dropout_ragged(
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model: Model[InT, InT], Xr: Ragged, is_train: bool
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) -> Tuple[Ragged, Callable]:
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X = Xr.data
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lengths = Xr.lengths
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mask = model.ops.get_dropout_mask(X.shape, model.attrs["dropout_rate"])
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Y = X * mask
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def backprop(dYr: Ragged) -> Ragged:
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return Ragged(dYr.data * mask, dYr.lengths)
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return Ragged(Y, lengths), backprop
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def _dropout_lists(
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model: Model[InT, InT], Xs: Sequence[ArrayXd], is_train: bool
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) -> Tuple[Sequence[ArrayXd], Callable]:
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rate = model.attrs["dropout_rate"]
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masks = [model.ops.get_dropout_mask(X.shape, rate) for X in Xs]
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Ys = [X * mask for X, mask in zip(Xs, masks)]
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def backprop(dYs: List[ArrayXd]) -> List[ArrayXd]:
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return [dY * mask for dY, mask in zip(dYs, masks)]
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return Ys, backprop
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