#pragma once
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#include <stdint.h>
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#include <memory>
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#include <mutex>
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#include <deque>
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#include <atomic>
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#include <typeinfo>
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#include <utility>
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#include <c10/util/Exception.h>
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#include <c10/util/C++17.h>
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#include <c10/core/Device.h>
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/**
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* Note [Generator]
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* ~~~~~~~~~~~~~~~~
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* A Pseudo Random Number Generator (PRNG) is an engine that uses an algorithm to
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* generate a seemingly random sequence of numbers, that may be later be used in creating
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* a random distribution. Such an engine almost always maintains a state and requires a
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* seed to start off the creation of random numbers. Often times, users have
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* found it beneficial to be able to explicitly create, retain, and destroy
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* PRNG states and also be able to have control over the seed value.
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*
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* A Generator in ATen gives users the ability to read, write and modify a PRNG engine.
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* For instance, it does so by letting users seed a PRNG engine, fork the state of the
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* engine, etc.
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*
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* By default, there is one generator per device, and a device's generator is
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* lazily created. A user can use the torch.Generator() api to create their own generator.
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* Currently torch.Generator() can only create a CPUGenerator.
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*/
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/**
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* Note [Acquire lock when using random generators]
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* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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* Generator and its derived classes are NOT thread-safe. Please note that most of the
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* places where we have inserted locking for generators are historically based, and we
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* haven't actually checked that everything is truly thread safe (and it probably isn't).
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* Please use the public mutex_ when using any methods from these classes, except for the
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* read-only methods. You can learn about the usage by looking into the unittests
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* (aten/src/ATen/cpu_generator_test.cpp) and other places where we have used lock_guard.
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*
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* TODO: Look into changing the threading semantics of Generators in ATen (e.g., making
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* them non-thread safe and instead making the generator state splittable, to accommodate
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* forks into other threads).
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*/
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namespace at {
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// The default seed is selected to be a large number
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// with good distribution of 0s and 1s in bit representation
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constexpr uint64_t default_rng_seed_val = 67280421310721;
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struct CAFFE2_API Generator {
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// Constructors
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Generator(Device device_in);
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// Delete all copy and move assignment in favor of clone()
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// method
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Generator(const Generator& other) = delete;
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Generator(Generator&& other) = delete;
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Generator& operator=(const Generator& other) = delete;
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virtual ~Generator() = default;
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std::shared_ptr<Generator> clone() const;
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// Common methods for all generators
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virtual void set_current_seed(uint64_t seed) = 0;
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virtual uint64_t current_seed() const = 0;
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virtual uint64_t seed() = 0;
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Device device() const;
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// See Note [Acquire lock when using random generators]
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std::mutex mutex_;
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private:
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Device device_;
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virtual Generator* clone_impl() const = 0;
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};
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namespace detail {
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CAFFE2_API uint64_t getNonDeterministicRandom(bool is_cuda = false);
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} // namespace detail
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} // namespace at
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