78 lines
2.2 KiB
C++
78 lines
2.2 KiB
C++
// Copyright 2010-2018 Google LLC
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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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#ifndef OR_TOOLS_BASE_RANDOM_H_
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#define OR_TOOLS_BASE_RANDOM_H_
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#include <random>
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#include <string>
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#include "absl/random/random.h"
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#include "ortools/base/basictypes.h"
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namespace operations_research {
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// A wrapper around std::mt19937. Called ACMRandom for historical reasons.
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class ACMRandom {
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public:
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explicit ACMRandom(int32 seed) : generator_(seed) {}
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// Unbounded generators.
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uint32 Next();
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uint64 Next64();
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uint64 Rand64() { return Next64(); }
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uint64 operator()() { return Next64(); }
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// Bounded generators.
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uint32 Uniform(uint32 n);
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uint64 operator()(uint64 val_max);
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// Seed management.
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void Reset(int32 seed) { generator_.seed(seed); }
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static int32 HostnamePidTimeSeed();
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static int32 DeterministicSeed();
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// C++11 goodies.
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typedef int64 difference_type;
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typedef uint64 result_type;
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static constexpr result_type min() { return 0; }
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static constexpr result_type max() { return kuint32max; }
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private:
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std::mt19937 generator_;
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};
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class MTRandom : public ACMRandom {
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public:
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explicit MTRandom(int32 seed) : ACMRandom(seed) {}
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// MTRandom also supports a std::string seed.
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explicit MTRandom(const std::string& str_seed)
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: ACMRandom(GenerateInt32SeedFromString(str_seed)) {}
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MTRandom() : ACMRandom(ACMRandom::HostnamePidTimeSeed()) {}
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private:
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int32 GenerateInt32SeedFromString(const std::string& str) {
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uint32 seed = 1234567;
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for (size_t i = 0; i < str.size(); ++i) {
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seed *= 1000003; // prime
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seed += static_cast<uint32>(str[i]);
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}
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return seed >> 1; // Will fit into an int32.
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}
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};
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} // namespace operations_research
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#endif // OR_TOOLS_BASE_RANDOM_H_
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