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d62c614695
Distinguish between "rendered" and "unrendered" Tensors.
There are now three types of `Tensor`:
- `Tensor Value a`: rendered value
- `Tensor Ref a`: rendered reference
- `Tensor Build a` : unrendered value
The extra bookkeeping makes it easier to track (and enforce) which tensors are
rendered or not. For examples where this has been confusing in the past, see
With this change, pure ops look similar to before, returning `Tensor Build`
instead of `Tensor Value`. "Stateful" (monadic) ops are unchanged. For
example:
add :: OneOf [..] t => Tensor v'1 t -> Tensor v'2 t -> Tensor Build t
assign :: (MonadBuild m, TensorType t)
=> Tensor Ref t -> Tensor v'2 t -> m (Tensor Ref t)
The `gradients` function now requires that the variables over which it's
differentiating are pre-rendered:
gradients :: (..., Rendered v2) => Tensor v1 a -> [Tensor v2 a]
-> m [Tensor Value a]
(`Rendered v2` means that `v2` is either a `Ref` or a `Value`.)
Additionally, the implementation of `gradients` now takes care to render every
intermediate value when performing the reverse accumulation. I suspect this
fixes an exponential blowup for complicated expressions.
50 lines
1.6 KiB
Haskell
50 lines
1.6 KiB
Haskell
-- Copyright 2016 TensorFlow authors.
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--
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-- Licensed under the Apache License, Version 2.0 (the "License");
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-- you may not use this file except in compliance with the License.
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-- You may obtain a copy of the License at
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--
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-- http://www.apache.org/licenses/LICENSE-2.0
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--
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-- Unless required by applicable law or agreed to in writing, software
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-- distributed under the License is distributed on an "AS IS" BASIS,
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-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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-- See the License for the specific language governing permissions and
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-- limitations under the License.
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{-# LANGUAGE GADTs #-}
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{-# LANGUAGE OverloadedStrings #-}
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{-# LANGUAGE RankNTypes #-}
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{-# LANGUAGE ScopedTypeVariables #-}
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module TensorFlow.ControlFlow
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( -- * Dependencies
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withControlDependencies
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, group
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-- * Operations
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, noOp
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) where
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import TensorFlow.BuildOp
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import TensorFlow.Build
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import TensorFlow.Nodes
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-- | Modify a 'Build' action, such that all new ops rendered in it will depend
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-- on the nodes in the first argument.
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withControlDependencies :: (MonadBuild m, Nodes t) => t -> m a -> m a
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withControlDependencies deps act = do
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nodes <- build $ getNodes deps
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withNodeDependencies nodes act
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-- TODO(judahjacobson): Reimplement withDependencies.
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-- | Create an op that groups multiple operations.
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--
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-- When this op finishes, all ops in the input @n@ have finished. This op has
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-- no output.
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group :: (MonadBuild m, Nodes t) => t -> m ControlNode
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group deps = withControlDependencies deps noOp
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-- | Does nothing. Only useful as a placeholder for control edges.
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noOp :: MonadBuild m => m ControlNode
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noOp = build $ buildOp [] $ opDef "NoOp"
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