1 | #pragma once |
2 | |
3 | #include <stdint.h> |
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 uint64_t current_seed() const = 0; |
71 | virtual uint64_t seed() = 0; |
72 | virtual void set_state(const c10::TensorImpl& new_state) = 0; |
73 | virtual c10::intrusive_ptr<c10::TensorImpl> get_state() const = 0; |
74 | Device device() const; |
75 | |
76 | // See Note [Acquire lock when using random generators] |
77 | std::mutex mutex_; |
78 | |
79 | DispatchKeySet key_set() const { |
80 | return key_set_; |
81 | } |
82 | |
83 | inline void set_pyobj(PyObject* pyobj) noexcept { |
84 | pyobj_ = pyobj; |
85 | } |
86 | |
87 | inline PyObject* pyobj() const noexcept { |
88 | return pyobj_; |
89 | } |
90 | |
91 | protected: |
92 | Device device_; |
93 | DispatchKeySet key_set_; |
94 | PyObject* pyobj_ = nullptr; |
95 | |
96 | virtual GeneratorImpl* clone_impl() const = 0; |
97 | }; |
98 | |
99 | namespace detail { |
100 | |
101 | C10_API uint64_t getNonDeterministicRandom(bool is_cuda = false); |
102 | |
103 | } // namespace detail |
104 | |
105 | } // namespace c10 |
106 | |