59 lines
2.3 KiB
C++
59 lines
2.3 KiB
C++
/* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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==============================================================================*/
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#ifndef TENSORFLOW_COMPILER_XLA_SERVICE_TREE_REDUCTION_REWRITER_H_
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#define TENSORFLOW_COMPILER_XLA_SERVICE_TREE_REDUCTION_REWRITER_H_
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#include <utility>
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#include "absl/strings/string_view.h"
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#include "tensorflow/compiler/xla/service/hlo_module.h"
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#include "tensorflow/compiler/xla/service/hlo_pass_interface.h"
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#include "tensorflow/compiler/xla/statusor.h"
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namespace xla {
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// Increase precision for the reduction operation by applying the reduce-window
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// first.
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//
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// E.g. suppose we want to reduce f32[1024] to a scalar. This pass first applies
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// a reduce-window (with kSame padding) of size `reduce_window_size`, and then
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// reduces the resulting array f32[32]. The rewrite is not applied if any of the
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// reduced dimensions is smaller than the `reduce_window_size`.
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//
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// Applying this pass until a fixed point performs a variant of pairwise
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// summation (https://en.wikipedia.org/wiki/Pairwise_summation), which is
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// guaranteed to have an asymptotically smaller error bound provided that
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// intermediate roundoff errors are random and have random sign.
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//
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// If this pass lowers the performance too much, the window size can always be
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// increased to a larger value.
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class TreeReductionRewriter : public HloModulePass {
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public:
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explicit TreeReductionRewriter(int64 reduce_window_size = 32)
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: reduce_window_size_(reduce_window_size) {}
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~TreeReductionRewriter() override = default;
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absl::string_view name() const override { return "tree_reduction_rewriter"; }
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StatusOr<bool> Run(HloModule* module) override;
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private:
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int64 reduce_window_size_;
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};
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} // end namespace xla
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#endif // TENSORFLOW_COMPILER_XLA_SERVICE_TREE_REDUCTION_REWRITER_H_
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