Source code for torchrl.data.map.hash
# Copyright (c) Meta Platforms, Inc. and affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
from __future__ import annotations
from typing import Callable, List
import torch
from torch.nn import Module
[docs]class BinaryToDecimal(Module):
"""A Module to convert binaries encoded tensors to decimals.
This is a utility class that allow to convert a binary encoding tensor (e.g. `1001`) to
its decimal value (e.g. `9`)
Args:
num_bits (int): the number of bits to use for the bases table.
The number of bits must be lower or equal to the input length and the input length
must be divisible by ``num_bits``. If ``num_bits`` is lower than the number of
bits in the input, the end result will be aggregated on the last dimension using
:func:`~torch.sum`.
device (torch.device): the device where inputs and outputs are to be expected.
dtype (torch.dtype): the output dtype.
convert_to_binary (bool, optional): if ``True``, the input to the ``forward``
method will be cast to a binary input using :func:`~torch.heavyside`.
Defaults to ``False``.
Examples:
>>> binary_to_decimal = BinaryToDecimal(
... num_bits=4, device="cpu", dtype=torch.int32, convert_to_binary=True
... )
>>> binary = torch.Tensor([[0, 0, 1, 0, 0, 0, 0, 1], [0, 0, 0, 0, 0, 0, 10, 0]])
>>> decimal = binary_to_decimal(binary)
>>> assert decimal.shape == (2,)
>>> assert (decimal == torch.Tensor([3, 2])).all()
"""
def __init__(
self,
num_bits: int,
device: torch.device,
dtype: torch.dtype,
convert_to_binary: bool = False,
):
super().__init__()
self.convert_to_binary = convert_to_binary
self.bases = 2 ** torch.arange(num_bits - 1, -1, -1, device=device, dtype=dtype)
self.num_bits = num_bits
self.zero_tensor = torch.zeros((1,), device=device)
[docs] def forward(self, features: torch.Tensor) -> torch.Tensor:
num_features = features.shape[-1]
if self.num_bits > num_features:
raise ValueError(f"{num_features=} is less than {self.num_bits=}")
elif num_features % self.num_bits != 0:
raise ValueError(f"{num_features=} is not divisible by {self.num_bits=}")
binary_features = (
torch.heaviside(features, self.zero_tensor)
if self.convert_to_binary
else features
)
feature_parts = binary_features.reshape(shape=(-1, self.num_bits))
digits = torch.vmap(torch.dot, (None, 0))(
self.bases, feature_parts.to(self.bases.dtype)
)
digits = digits.reshape(shape=(-1, features.shape[-1] // self.num_bits))
aggregated_digits = torch.sum(digits, dim=-1)
return aggregated_digits
[docs]class SipHash(Module):
"""A Module to Compute SipHash values for given tensors.
A hash function module based on SipHash implementation in python. Input tensors should have shape ``[batch_size, num_features]``
and the output shape will be ``[batch_size]``.
Args:
as_tensor (bool, optional): if ``True``, the bytes will be turned into integers
through the builtin ``hash`` function and mapped to a tensor. Default: ``True``.
.. warning:: This module relies on the builtin ``hash`` function.
To get reproducible results across runs, the ``PYTHONHASHSEED`` environment
variable must be set before the code is run (changing this value during code
execution is without effect).
Examples:
>>> # Assuming we set PYTHONHASHSEED=0 prior to running this code
>>> a = torch.tensor([[0.1, 0.2], [0.3, 0.4], [0.5, 0.6]])
>>> b = a.clone()
>>> hash_module = SipHash(as_tensor=True)
>>> hash_a = hash_module(a)
>>> hash_a
tensor([-4669941682990263259, -3778166555168484291, -9122128731510687521])
>>> hash_b = hash_module(b)
>>> assert (hash_a == hash_b).all()
"""
def __init__(self, as_tensor: bool = True):
super().__init__()
self.as_tensor = as_tensor
[docs] def forward(self, x: torch.Tensor) -> torch.Tensor | List[bytes]:
hash_values = []
if x.dtype in (torch.bfloat16,):
x = x.to(torch.float16)
for x_i in x.detach().cpu().numpy():
hash_value = x_i.tobytes()
hash_values.append(hash_value)
if not self.as_tensor:
return hash_values
result = torch.tensor([hash(x) for x in hash_values], dtype=torch.int64)
return result
[docs]class RandomProjectionHash(SipHash):
"""A module that combines random projections with SipHash to get a low-dimensional tensor, easier to embed through :class:`~.SipHash`.
This module requires sklearn to be installed.
Keyword Args:
n_components (int, optional): the low-dimensional number of components of the projections.
Defaults to 16.
dtype_cast (torch.dtype, optional): the dtype to cast the projection to.
Defaults to ``torch.bfloat16``.
as_tensor (bool, optional): if ``True``, the bytes will be turned into integers
through the builtin ``hash`` function and mapped to a tensor. Default: ``True``.
.. warning:: This module relies on the builtin ``hash`` function.
To get reproducible results across runs, the ``PYTHONHASHSEED`` environment
variable must be set before the code is run (changing this value during code
execution is without effect).
init_method: TODO
"""
_N_COMPONENTS_DEFAULT = 16
def __init__(
self,
*,
n_components: int | None = None,
dtype_cast=torch.bfloat16,
as_tensor: bool = True,
init_method: Callable[[torch.Tensor], torch.Tensor | None] | None = None,
**kwargs,
):
if n_components is None:
n_components = self._N_COMPONENTS_DEFAULT
super().__init__(as_tensor=as_tensor)
self.register_buffer("_n_components", torch.as_tensor(n_components))
self._init = False
if init_method is None:
init_method = torch.nn.init.normal_
self.init_method = init_method
self.dtype_cast = dtype_cast
self.register_buffer("transform", torch.nn.UninitializedBuffer())
@property
def n_components(self):
return self._n_components.item()
[docs] def fit(self, x):
"""Fits the random projection to the input data."""
self.transform.materialize(
(x.shape[-1], self.n_components), dtype=self.dtype_cast, device=x.device
)
self.init_method(self.transform)
self._init = True
[docs] def forward(self, x: torch.Tensor) -> torch.Tensor:
if not self._init:
self.fit(x)
elif not self._init:
raise RuntimeError(
f"The {type(self).__name__} has not been initialized. Call fit before calling this method."
)
x = x.to(self.dtype_cast) @ self.transform
return super().forward(x)
