# Source code for captum.attr._core.neuron.neuron_deep_lift

```
#!/usr/bin/env python3
from typing import Any, Callable, cast, Tuple, Union
from captum._utils.gradient import construct_neuron_grad_fn
from captum._utils.typing import BaselineType, TensorOrTupleOfTensorsGeneric
from captum.attr._core.deep_lift import DeepLift, DeepLiftShap
from captum.attr._utils.attribution import GradientAttribution, NeuronAttribution
from captum.log import log_usage
from torch import Tensor
from torch.nn import Module
[docs]
class NeuronDeepLift(NeuronAttribution, GradientAttribution):
r"""
Implements DeepLIFT algorithm for the neuron based on the following paper:
Learning Important Features Through Propagating Activation Differences,
Avanti Shrikumar, et. al.
https://arxiv.org/abs/1704.02685
and the gradient formulation proposed in:
Towards better understanding of gradient-based attribution methods for
deep neural networks, Marco Ancona, et.al.
https://openreview.net/pdf?id=Sy21R9JAW
This implementation supports only Rescale rule. RevealCancel rule will
be supported in later releases.
Although DeepLIFT's(Rescale Rule) attribution quality is comparable with
Integrated Gradients, it runs significantly faster than Integrated
Gradients and is preferred for large datasets.
Currently we only support a limited number of non-linear activations
but the plan is to expand the list in the future.
Note: As we know, currently we cannot access the building blocks,
of PyTorch's built-in LSTM, RNNs and GRUs such as Tanh and Sigmoid.
Nonetheless, it is possible to build custom LSTMs, RNNS and GRUs
with performance similar to built-in ones using TorchScript.
More details on how to build custom RNNs can be found here:
https://pytorch.org/blog/optimizing-cuda-rnn-with-torchscript/
"""
def __init__(
self, model: Module, layer: Module, multiply_by_inputs: bool = True
) -> None:
r"""
Args:
model (nn.Module): The reference to PyTorch model instance.
layer (torch.nn.Module): Layer for which neuron attributions are computed.
Attributions for a particular neuron for the input or output
of this layer are computed using the argument neuron_selector
in the attribute method.
Currently, it is assumed that the inputs or the outputs
of the layer, depending on which one is used for
attribution, can only be a single tensor.
multiply_by_inputs (bool, optional): Indicates whether to factor
model inputs' multiplier in the final attribution scores.
In the literature this is also known as local vs global
attribution. If inputs' multiplier isn't factored in
then that type of attribution method is also called local
attribution. If it is, then that type of attribution
method is called global.
More detailed can be found here:
https://arxiv.org/abs/1711.06104
In case of Neuron DeepLift, if `multiply_by_inputs`
is set to True, final sensitivity scores
are being multiplied by (inputs - baselines).
This flag applies only if `custom_attribution_func` is
set to None.
"""
NeuronAttribution.__init__(self, model, layer)
GradientAttribution.__init__(self, model)
self._multiply_by_inputs = multiply_by_inputs
[docs]
@log_usage()
def attribute(
self,
inputs: TensorOrTupleOfTensorsGeneric,
neuron_selector: Union[int, Tuple[Union[int, slice], ...], Callable],
baselines: BaselineType = None,
additional_forward_args: Any = None,
attribute_to_neuron_input: bool = False,
custom_attribution_func: Union[None, Callable[..., Tuple[Tensor, ...]]] = None,
) -> TensorOrTupleOfTensorsGeneric:
r"""
Args:
inputs (Tensor or tuple[Tensor, ...]): Input for which layer
attributions are computed. If model takes a
single tensor as input, a single input tensor should be
provided. If model takes multiple tensors as input,
a tuple of the input tensors should be provided. It is
assumed that for all given input tensors, dimension 0
corresponds to the number of examples (aka batch size),
and if multiple input tensors are provided, the examples
must be aligned appropriately.
neuron_selector (int, Callable, tuple[int], or slice):
Selector for neuron
in given layer for which attribution is desired.
Neuron selector can be provided as:
- a single integer, if the layer output is 2D. This integer
selects the appropriate neuron column in the layer input
or output
- a tuple of integers or slice objects. Length of this
tuple must be one less than the number of dimensions
in the input / output of the given layer (since
dimension 0 corresponds to number of examples).
The elements of the tuple can be either integers or
slice objects (slice object allows indexing a
range of neurons rather individual ones).
If any of the tuple elements is a slice object, the
indexed output tensor is used for attribution. Note
that specifying a slice of a tensor would amount to
computing the attribution of the sum of the specified
neurons, and not the individual neurons independently.
- a callable, which should
take the target layer as input (single tensor or tuple
if multiple tensors are in layer) and return a neuron or
aggregate of the layer's neurons for attribution.
For example, this function could return the
sum of the neurons in the layer or sum of neurons with
activations in a particular range. It is expected that
this function returns either a tensor with one element
or a 1D tensor with length equal to batch_size (one scalar
per input example)
baselines (scalar, Tensor, tuple of scalar, or Tensor, optional):
Baselines define reference samples that are compared with
the inputs. In order to assign attribution scores DeepLift
computes the differences between the inputs/outputs and
corresponding references.
Baselines can be provided as:
- a single tensor, if inputs is a single tensor, with
exactly the same dimensions as inputs or the first
dimension is one and the remaining dimensions match
with inputs.
- a single scalar, if inputs is a single tensor, which will
be broadcasted for each input value in input tensor.
- a tuple of tensors or scalars, the baseline corresponding
to each tensor in the inputs' tuple can be:
- either a tensor with matching dimensions to
corresponding tensor in the inputs' tuple
or the first dimension is one and the remaining
dimensions match with the corresponding
input tensor.
- or a scalar, corresponding to a tensor in the
inputs' tuple. This scalar value is broadcasted
for corresponding input tensor.
In the cases when `baselines` is not provided, we internally
use zero scalar corresponding to each input tensor.
Default: None
additional_forward_args (Any, optional): If the forward function
requires additional arguments other than the inputs for
which attributions should not be computed, this argument
can be provided. It must be either a single additional
argument of a Tensor or arbitrary (non-tuple) type or a tuple
containing multiple additional arguments including tensors
or any arbitrary python types. These arguments are provided
to model in order, following the arguments in inputs.
Note that attributions are not computed with respect
to these arguments.
Default: None
attribute_to_neuron_input (bool, optional): Indicates whether to
compute the attributions with respect to the neuron input
or output. If `attribute_to_neuron_input` is set to True
then the attributions will be computed with respect to
neuron's inputs, otherwise it will be computed with respect
to neuron's outputs.
Note that currently it is assumed that either the input
or the output of internal neuron, depending on whether we
attribute to the input or output, is a single tensor.
Support for multiple tensors will be added later.
Default: False
custom_attribution_func (Callable, optional): A custom function for
computing final attribution scores. This function can take
at least one and at most three arguments with the
following signature:
- custom_attribution_func(multipliers)
- custom_attribution_func(multipliers, inputs)
- custom_attribution_func(multipliers, inputs, baselines)
In case this function is not provided, we use the default
logic defined as: multipliers * (inputs - baselines)
It is assumed that all input arguments, `multipliers`,
`inputs` and `baselines` are provided in tuples of same
length. `custom_attribution_func` returns a tuple of
attribution tensors that have the same length as the
`inputs`.
Default: None
Returns:
**attributions** or 2-element tuple of **attributions**, **delta**:
- **attributions** (*Tensor* or *tuple[Tensor, ...]*):
Computes attributions using Deeplift's rescale rule for
particular neuron with respect to each input feature.
Attributions will always be the same size as the provided
inputs, with each value providing the attribution of the
corresponding input index.
If a single tensor is provided as inputs, a single tensor is
returned. If a tuple is provided for inputs, a tuple of
corresponding sized tensors is returned.
Examples::
>>> # ImageClassifier takes a single input tensor of images Nx3x32x32,
>>> # and returns an Nx10 tensor of class probabilities.
>>> net = ImageClassifier()
>>> # creates an instance of LayerDeepLift to interpret target
>>> # class 1 with respect to conv4 layer.
>>> dl = NeuronDeepLift(net, net.conv4)
>>> input = torch.randn(1, 3, 32, 32, requires_grad=True)
>>> # Computes deeplift attribution scores for conv4 layer and neuron
>>> # index (4,1,2).
>>> attribution = dl.attribute(input, (4,1,2))
"""
dl = DeepLift(cast(Module, self.forward_func), self.multiplies_by_inputs)
dl.gradient_func = construct_neuron_grad_fn(
self.layer,
neuron_selector,
attribute_to_neuron_input=attribute_to_neuron_input,
)
# NOTE: using __wrapped__ to not log
return dl.attribute.__wrapped__( # type: ignore
dl, # self
inputs,
baselines,
additional_forward_args=additional_forward_args,
custom_attribution_func=custom_attribution_func,
)
@property
def multiplies_by_inputs(self):
return self._multiply_by_inputs
[docs]
class NeuronDeepLiftShap(NeuronAttribution, GradientAttribution):
r"""
Extends NeuronAttribution and uses LayerDeepLiftShap algorithms and
approximates SHAP values for given input `layer` and `neuron_selector`.
For each input sample - baseline pair it computes DeepLift attributions
with respect to inputs or outputs of given `layer` and `neuron_selector`
averages resulting attributions across baselines. Whether to compute the
attributions with respect to the inputs or outputs of the layer is defined
by the input flag `attribute_to_layer_input`.
More details about the algorithm can be found here:
https://papers.nips.cc/paper/7062-a-unified-approach-to-interpreting-model-predictions.pdf
Note that the explanation model:
1. Assumes that input features are independent of one another
2. Is linear, meaning that the explanations are modeled through
the additive composition of feature effects.
Although, it assumes a linear model for each explanation, the overall
model across multiple explanations can be complex and non-linear.
"""
def __init__(
self, model: Module, layer: Module, multiply_by_inputs: bool = True
) -> None:
r"""
Args:
model (nn.Module): The reference to PyTorch model instance.
layer (torch.nn.Module): Layer for which neuron attributions are computed.
Attributions for a particular neuron for the input or output
of this layer are computed using the argument neuron_selector
in the attribute method.
Currently, only layers with a single tensor input and output
are supported.
multiply_by_inputs (bool, optional): Indicates whether to factor
model inputs' multiplier in the final attribution scores.
In the literature this is also known as local vs global
attribution. If inputs' multiplier isn't factored in
then that type of attribution method is also called local
attribution. If it is, then that type of attribution
method is called global.
More detailed can be found here:
https://arxiv.org/abs/1711.06104
In case of Neuron DeepLift Shap, if `multiply_by_inputs`
is set to True, final sensitivity scores
are being multiplied by (inputs - baselines).
This flag applies only if `custom_attribution_func` is
set to None.
"""
NeuronAttribution.__init__(self, model, layer)
GradientAttribution.__init__(self, model)
self._multiply_by_inputs = multiply_by_inputs
[docs]
@log_usage()
def attribute(
self,
inputs: TensorOrTupleOfTensorsGeneric,
neuron_selector: Union[int, Tuple[Union[int, slice], ...], Callable],
baselines: Union[
TensorOrTupleOfTensorsGeneric, Callable[..., TensorOrTupleOfTensorsGeneric]
],
additional_forward_args: Any = None,
attribute_to_neuron_input: bool = False,
custom_attribution_func: Union[None, Callable[..., Tuple[Tensor, ...]]] = None,
) -> TensorOrTupleOfTensorsGeneric:
r"""
Args:
inputs (Tensor or tuple[Tensor, ...]): Input for which layer
attributions are computed. If model takes a
single tensor as input, a single input tensor should be
provided. If model takes multiple tensors as input,
a tuple of the input tensors should be provided. It is
assumed that for all given input tensors, dimension 0
corresponds to the number of examples (aka batch size),
and if multiple input tensors are provided, the examples
must be aligned appropriately.
neuron_selector (int, Callable, tuple[int], or slice):
Selector for neuron
in given layer for which attribution is desired.
Neuron selector can be provided as:
- a single integer, if the layer output is 2D. This integer
selects the appropriate neuron column in the layer input
or output
- a tuple of integers or slice objects. Length of this
tuple must be one less than the number of dimensions
in the input / output of the given layer (since
dimension 0 corresponds to number of examples).
The elements of the tuple can be either integers or
slice objects (slice object allows indexing a
range of neurons rather individual ones).
If any of the tuple elements is a slice object, the
indexed output tensor is used for attribution. Note
that specifying a slice of a tensor would amount to
computing the attribution of the sum of the specified
neurons, and not the individual neurons independently.
- a callable, which should
take the target layer as input (single tensor or tuple
if multiple tensors are in layer) and return a neuron or
aggregate of the layer's neurons for attribution.
For example, this function could return the
sum of the neurons in the layer or sum of neurons with
activations in a particular range. It is expected that
this function returns either a tensor with one element
or a 1D tensor with length equal to batch_size (one scalar
per input example)
baselines (Tensor, tuple[Tensor, ...], or Callable):
Baselines define reference samples that are compared with
the inputs. In order to assign attribution scores DeepLift
computes the differences between the inputs/outputs and
corresponding references. Baselines can be provided as:
- a single tensor, if inputs is a single tensor, with
the first dimension equal to the number of examples
in the baselines' distribution. The remaining dimensions
must match with input tensor's dimension starting from
the second dimension.
- a tuple of tensors, if inputs is a tuple of tensors,
with the first dimension of any tensor inside the tuple
equal to the number of examples in the baseline's
distribution. The remaining dimensions must match
the dimensions of the corresponding input tensor
starting from the second dimension.
- callable function, optionally takes `inputs` as an
argument and either returns a single tensor
or a tuple of those.
It is recommended that the number of samples in the baselines'
tensors is larger than one.
additional_forward_args (Any, optional): If the forward function
requires additional arguments other than the inputs for
which attributions should not be computed, this argument
can be provided. It must be either a single additional
argument of a Tensor or arbitrary (non-tuple) type or a tuple
containing multiple additional arguments including tensors
or any arbitrary python types. These arguments are provided
to model in order, following the arguments in inputs.
Note that attributions are not computed with respect
to these arguments.
Default: None
attribute_to_neuron_input (bool, optional): Indicates whether to
compute the attributions with respect to the neuron input
or output. If `attribute_to_neuron_input` is set to True
then the attributions will be computed with respect to
neuron's inputs, otherwise it will be computed with respect
to neuron's outputs.
Note that currently it is assumed that either the input
or the output of internal neuron, depending on whether we
attribute to the input or output, is a single tensor.
Support for multiple tensors will be added later.
Default: False
custom_attribution_func (Callable, optional): A custom function for
computing final attribution scores. This function can take
at least one and at most three arguments with the
following signature:
- custom_attribution_func(multipliers)
- custom_attribution_func(multipliers, inputs)
- custom_attribution_func(multipliers, inputs, baselines)
In case this function is not provided, we use the default
logic defined as: multipliers * (inputs - baselines)
It is assumed that all input arguments, `multipliers`,
`inputs` and `baselines` are provided in tuples of same
length. `custom_attribution_func` returns a tuple of
attribution tensors that have the same length as the
`inputs`.
Default: None
Returns:
**attributions** or 2-element tuple of **attributions**, **delta**:
- **attributions** (*Tensor* or *tuple[Tensor, ...]*):
Computes attributions using Deeplift's rescale rule for
particular neuron with respect to each input feature.
Attributions will always be the same size as the provided
inputs, with each value providing the attribution of the
corresponding input index.
If a single tensor is provided as inputs, a single tensor is
returned. If a tuple is provided for inputs, a tuple of
corresponding sized tensors is returned.
Examples::
>>> # ImageClassifier takes a single input tensor of images Nx3x32x32,
>>> # and returns an Nx10 tensor of class probabilities.
>>> net = ImageClassifier()
>>> # creates an instance of LayerDeepLift to interpret target
>>> # class 1 with respect to conv4 layer.
>>> dl = NeuronDeepLiftShap(net, net.conv4)
>>> input = torch.randn(1, 3, 32, 32, requires_grad=True)
>>> # Computes deeplift attribution scores for conv4 layer and neuron
>>> # index (4,1,2).
>>> attribution = dl.attribute(input, (4,1,2))
"""
dl = DeepLiftShap(cast(Module, self.forward_func), self.multiplies_by_inputs)
dl.gradient_func = construct_neuron_grad_fn(
self.layer,
neuron_selector,
attribute_to_neuron_input=attribute_to_neuron_input,
)
# NOTE: using __wrapped__ to not log
return dl.attribute.__wrapped__( # type: ignore
dl, # self
inputs,
baselines,
additional_forward_args=additional_forward_args,
custom_attribution_func=custom_attribution_func,
)
@property
def multiplies_by_inputs(self):
return self._multiply_by_inputs
```