1 #pragma once 2 3 #include <cstdint> 4 #include <mutex> 5 6 #include <c10/core/Device.h> 7 #include <c10/core/DispatchKeySet.h> 8 #include <c10/core/TensorImpl.h> 9 #include <c10/macros/Export.h> 10 #include <c10/util/intrusive_ptr.h> 11 #include <c10/util/python_stub.h> 12 13 /** 14 * Note [Generator] 15 * ~~~~~~~~~~~~~~~~ 16 * A Pseudo Random Number Generator (PRNG) is an engine that uses an algorithm 17 * to generate a seemingly random sequence of numbers, that may be later be used 18 * in creating a random distribution. Such an engine almost always maintains a 19 * state and requires a seed to start off the creation of random numbers. Often 20 * times, users have found it beneficial to be able to explicitly create, 21 * retain, and destroy PRNG states and also be able to have control over the 22 * seed value. 23 * 24 * A Generator in ATen gives users the ability to read, write and modify a PRNG 25 * engine. For instance, it does so by letting users seed a PRNG engine, fork 26 * the state of the engine, etc. 27 * 28 * By default, there is one generator per device, and a device's generator is 29 * lazily created. A user can use the torch.Generator() api to create their own 30 * generator. Currently torch.Generator() can only create a CPUGeneratorImpl. 31 */ 32 33 /** 34 * Note [Acquire lock when using random generators] 35 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 36 * Generator and its derived classes are NOT thread-safe. Please note that most 37 * of the places where we have inserted locking for generators are historically 38 * based, and we haven't actually checked that everything is truly thread safe 39 * (and it probably isn't). Please use the public mutex_ when using any methods 40 * from these classes, except for the read-only methods. You can learn about the 41 * usage by looking into the unittests (aten/src/ATen/cpu_generator_test.cpp) 42 * and other places where we have used lock_guard. 43 * 44 * TODO: Look into changing the threading semantics of Generators in ATen (e.g., 45 * making them non-thread safe and instead making the generator state 46 * splittable, to accommodate forks into other threads). 47 */ 48 49 namespace c10 { 50 51 // The default seed is selected to be a large number 52 // with good distribution of 0s and 1s in bit representation 53 constexpr uint64_t default_rng_seed_val = 67280421310721; 54 55 struct C10_API GeneratorImpl : public c10::intrusive_ptr_target { 56 // Constructors 57 GeneratorImpl(Device device_in, DispatchKeySet key_set); 58 59 // Delete all copy and move assignment in favor of clone() 60 // method 61 GeneratorImpl(const GeneratorImpl& other) = delete; 62 GeneratorImpl(GeneratorImpl&& other) = delete; 63 GeneratorImpl& operator=(const GeneratorImpl& other) = delete; 64 65 ~GeneratorImpl() override = default; 66 c10::intrusive_ptr<GeneratorImpl> clone() const; 67 68 // Common methods for all generators 69 virtual void set_current_seed(uint64_t seed) = 0; 70 virtual void set_offset(uint64_t offset) = 0; 71 virtual uint64_t get_offset() const = 0; 72 virtual uint64_t current_seed() const = 0; 73 virtual uint64_t seed() = 0; 74 virtual void set_state(const c10::TensorImpl& new_state) = 0; 75 virtual c10::intrusive_ptr<c10::TensorImpl> get_state() const = 0; 76 virtual void graphsafe_set_state( 77 const c10::intrusive_ptr<c10::GeneratorImpl>& new_state); 78 virtual c10::intrusive_ptr<c10::GeneratorImpl> graphsafe_get_state() const; 79 Device device() const; 80 81 // See Note [Acquire lock when using random generators] 82 std::mutex mutex_; 83 key_setGeneratorImpl84 DispatchKeySet key_set() const { 85 return key_set_; 86 } 87 set_pyobjGeneratorImpl88 inline void set_pyobj(PyObject* pyobj) noexcept { 89 pyobj_ = pyobj; 90 } 91 pyobjGeneratorImpl92 inline PyObject* pyobj() const noexcept { 93 return pyobj_; 94 } 95 96 protected: 97 Device device_; 98 DispatchKeySet key_set_; 99 PyObject* pyobj_ = nullptr; 100 101 virtual GeneratorImpl* clone_impl() const = 0; 102 }; 103 104 namespace detail { 105 106 C10_API uint64_t getNonDeterministicRandom(bool is_cuda = false); 107 108 } // namespace detail 109 110 } // namespace c10 111