View Source Nx.Random (Nx v0.4.0)
Pseudo-random number generators.
Unlike the stateful pseudo-random number generators (PRNGs)
that users of most programming languages and numerical libraries
may be accustomed to, Nx random functions require an explicit
PRNG key to be passed as a first argument. That key is defined by
an Nx.Tensor composed of 2 unsigned 32-bit integers, usually
generated by the Nx.Random.key/1 function:
iex> Nx.Random.key(12)
#Nx.Tensor<
u32[2]
[0, 12]
>This key can then be used in any of Nx’s random number generation routines:
iex> key = Nx.Random.key(12)
iex> {uniform, _new_key} = Nx.Random.uniform(key)
iex> uniform
#Nx.Tensor<
f32
0.7691127061843872
>Now, when generating a new random number, you pass the new_key
to get a different number.
design-and-context
Design and Context
In short, Nx's PRNGs are based on a Threefry counter PRNG associated to a functional array-oriented splitting model. To summarize, among other requirements, Nx's PRNG aims to:
Ensure reproducibility
Parallelize well, both in terms of vectorization (generating array values) and multi-replica, multi-core computation. In particular it should not use sequencing constraints between random function calls.
Link to this section Summary
Functions
Folds in new data to a PRNG key.
Create a pseudo-random number generator (PRNG) key given an integer seed.
Shortcut for normal(key, 0.0, 1.0, opts).
Returns a normal distribution with the given mean and standard_deviation.
Same as normal/4 but assumes the key has already been split.
Sample uniform random integer values in [min_value, max_value).
Same as randint/4 but assumes the key has already been split.
Splits a PRNG key into num new keys by adding a leading axis.
Shortcut for uniform(key, 0.0, 1.0, opts).
Sample uniform float values in [min_val, max_val).
Same as uniform/4 but assumes the key has already been split.
Link to this section Functions
Folds in new data to a PRNG key.
examples
Examples
iex> key = Nx.Random.key(42)
iex> Nx.Random.fold_in(key, 99)
#Nx.Tensor<
u32[2]
[2015327502, 1351855566]
>
iex> key = Nx.Random.key(42)
iex> Nx.Random.fold_in(key, 1234)
#Nx.Tensor<
u32[2]
[1356445167, 2917756949]
>
iex> key = Nx.Random.key(42)
iex> Nx.Random.fold_in(key, Nx.tensor([[1, 99], [1234, 13]]))
#Nx.Tensor<
u32[2][2][2]
[
[
[64467757, 2916123636],
[2015327502, 1351855566]
],
[
[1356445167, 2917756949],
[3514951389, 229662949]
]
]
>Create a pseudo-random number generator (PRNG) key given an integer seed.
examples
Examples
iex> Nx.Random.key(12)
#Nx.Tensor<
u32[2]
[0, 12]
>
iex> Nx.Random.key(999999999999)
#Nx.Tensor<
u32[2]
[232, 3567587327]
>Shortcut for normal(key, 0.0, 1.0, opts).
Returns a normal distribution with the given mean and standard_deviation.
options
Options
:type- a float or complex type for the returned tensor:shape- shape of the returned tensor:names- the names of the returned tensor
examples
Examples
iex> key = Nx.Random.key(42)
iex> {normal, _new_key} = Nx.Random.normal(key)
iex> normal
#Nx.Tensor<
f32
1.3694692850112915
>
iex> key = Nx.Random.key(42)
iex> {normal, _new_key} = Nx.Random.normal(key, 0, 1, shape: {3, 2}, type: :f16)
iex> normal
#Nx.Tensor<
f16[3][2]
[
[-0.326416015625, -0.7734375],
[0.3916015625, 0.533203125],
[0.27001953125, -2.083984375]
]
>
iex> key = Nx.Random.key(42)
iex> {normal, _new_key} = Nx.Random.normal(key, 0, 1, shape: {2, 2}, type: :c64)
iex> normal
#Nx.Tensor<
c64[2][2]
[
[-0.763276219367981+0.8661126494407654i, -0.14282897114753723-0.7384797930717468i],
[0.6784614324569702+0.4118310213088989i, -2.2695391178131104-0.3689095377922058i]
]
>
iex> key = Nx.Random.key(1337)
iex> {normal, _new_key} = Nx.Random.normal(key, 10, 5, shape: {1_000})
iex> Nx.mean(normal)
#Nx.Tensor<
f32
9.70021915435791
>
iex> Nx.standard_deviation(normal)
#Nx.Tensor<
f32
5.051421642303467
>Same as normal/4 but assumes the key has already been split.
Sample uniform random integer values in [min_value, max_value).
options
Options
:type- the integer type for the returned tensor:shape- shape of the returned tensor:names- the names of the returned tensor
examples
Examples
iex> key = Nx.Random.key(1701)
iex> {randint, _new_key} = Nx.Random.randint(key, 1, 100)
iex> randint
#Nx.Tensor<
s64
66
>
iex> key = Nx.Random.key(1701)
iex> {randint, _new_key} = Nx.Random.randint(key, 1, 100, shape: {3, 2}, type: :u32)
iex> randint
#Nx.Tensor<
u32[3][2]
[
[9, 20],
[19, 6],
[71, 15]
]
>Same as randint/4 but assumes the key has already been split.
Splits a PRNG key into num new keys by adding a leading axis.
examples
Examples
iex> key = Nx.Random.key(1701)
iex> Nx.Random.split(key)
#Nx.Tensor<
u32[2][2]
[
[56197195, 1801093307],
[961309823, 1704866707]
]
>
iex> key = Nx.Random.key(999999999999)
iex> Nx.Random.split(key, parts: 4)
#Nx.Tensor<
u32[4][2]
[
[3959978897, 4079927650],
[3769699049, 3585271160],
[3182829676, 333122445],
[3185556048, 1258545461]
]
>Shortcut for uniform(key, 0.0, 1.0, opts).
Sample uniform float values in [min_val, max_val).
options
Options
:type- a float type for the returned tensor:shape- shape of the returned tensor:names- the names of the returned tensor
examples
Examples
iex> key = Nx.Random.key(1701)
iex> {uniform, _new_key} = Nx.Random.uniform(key)
iex> uniform
#Nx.Tensor<
f32
0.9728643894195557
>
iex> key = Nx.Random.key(1701)
iex> {uniform, _new_key} = Nx.Random.uniform(key, shape: {3, 2}, type: :f16)
iex> uniform
#Nx.Tensor<
f16[3][2]
[
[0.75390625, 0.6484375],
[0.7294921875, 0.21484375],
[0.09765625, 0.0693359375]
]
>
iex> key = Nx.Random.key(1701)
iex> {uniform, _new_key} = Nx.Random.uniform(key, shape: {2, 2}, type: :c64)
iex> uniform
#Nx.Tensor<
c64[2][2]
[
[0.18404805660247803+0.6546461582183838i, 0.5525915622711182+0.11568140983581543i],
[0.6074584722518921+0.8104375600814819i, 0.247686505317688+0.21975469589233398i]
]
>Same as uniform/4 but assumes the key has already been split.