STT-tensorflow/tensorflow/compiler/xla/service/triangular_solve_expander.h
Peter Hawkins c9bd7f4e8a [XLA] Add an HLO implementation of a direct triangular solve, and use it for small matrices (n<32) with large batches (>8).
These sizes are chosen primarily for TPU; this implementation is not used on GPU and it is not tuned at all on CPU yet.

PiperOrigin-RevId: 340347289
Change-Id: I7d305f3ea84b389787830c66809965a1028a1b3d
2020-11-02 17:14:35 -08:00

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2.9 KiB
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/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/
#ifndef TENSORFLOW_COMPILER_XLA_SERVICE_TRIANGULAR_SOLVE_EXPANDER_H_
#define TENSORFLOW_COMPILER_XLA_SERVICE_TRIANGULAR_SOLVE_EXPANDER_H_
#include "absl/container/flat_hash_map.h"
#include "tensorflow/compiler/xla/client/xla_builder.h"
#include "tensorflow/compiler/xla/service/op_expander_pass.h"
namespace xla {
class TriangularSolveExpander : public OpExpanderPass {
public:
explicit TriangularSolveExpander(int64 block_size = 128);
absl::string_view name() const override {
return "triangular_solve_expander";
}
protected:
bool InstructionMatchesPattern(HloInstruction* instruction) override;
StatusOr<HloInstruction*> ExpandInstruction(
HloInstruction* instruction) override;
// Performs a triangular solve using an algorithm from MAGMA, which inverts
// diagonal blocks and multiplies them using matrix multiplications.
XlaOp SolveByInvertingDiagonalBlocks(XlaOp a, XlaOp b, bool left_side,
bool lower, bool transpose_a,
bool conjugate_a, bool unit_diagonal,
PrecisionConfig::Precision precision);
// Helper function used by SolveByInvertingDiagonalBlocks
virtual XlaOp InvertDiagonalBlocks(XlaOp diag_blocks, bool lower_triangular,
PrecisionConfig::Precision precision);
// Performs a direct triangular solve, suitable for case with small matrices
// or with large batch.
XlaOp SolveDirectly(XlaOp a, XlaOp b, bool left_side, bool lower,
bool transpose_a, bool conjugate_a, bool unit_diagonal,
PrecisionConfig::Precision precision);
XlaOp BuildTriangularSolve(XlaOp a, XlaOp b, bool left_side, bool lower,
bool transpose_a, bool conjugate_a,
bool unit_diagonal, int64 block_size,
PrecisionConfig::Precision precision);
private:
// Block size for BuildTriangularSolve
const int64 block_size_;
// Mapping from op signatures to existing computations.
absl::flat_hash_map<string, HloComputation*> computation_cache_;
};
} // namespace xla
#endif // TENSORFLOW_COMPILER_XLA_SERVICE_TRIANGULAR_SOLVE_EXPANDER_H_