# Source code for captum.attr._core.layer.layer_deep_lift

```
#!/usr/bin/env python3
import typing
from typing import Any, Callable, cast, Sequence, Tuple, Union
import torch
from captum._utils.common import (
_expand_target,
_format_additional_forward_args,
_format_baseline,
_format_tensor_into_tuples,
ExpansionTypes,
)
from captum._utils.gradient import compute_layer_gradients_and_eval
from captum._utils.typing import (
BaselineType,
Literal,
TargetType,
TensorOrTupleOfTensorsGeneric,
)
from captum.attr._core.deep_lift import DeepLift, DeepLiftShap
from captum.attr._utils.attribution import LayerAttribution
from captum.attr._utils.common import (
_call_custom_attribution_func,
_compute_conv_delta_and_format_attrs,
_format_callable_baseline,
_tensorize_baseline,
_validate_input,
)
from captum.log import log_usage
from torch import Tensor
from torch.nn import Module
[docs]
class LayerDeepLift(LayerAttribution, DeepLift):
r"""
Implements DeepLIFT algorithm for the layer 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 attributions are computed.
The size and dimensionality of the attributions
corresponds to the size and dimensionality of the layer's
input or output depending on whether we attribute to the
inputs or outputs of the layer.
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 Layer DeepLift, if `multiply_by_inputs`
is set to True, final sensitivity scores
are being multiplied by
layer activations for inputs - layer activations for baselines.
This flag applies only if `custom_attribution_func` is
set to None.
"""
LayerAttribution.__init__(self, model, layer)
DeepLift.__init__(self, model)
self.model = model
self._multiply_by_inputs = multiply_by_inputs
# Ignoring mypy error for inconsistent signature with DeepLift
@typing.overload # type: ignore
def attribute(
self,
inputs: Union[Tensor, Tuple[Tensor, ...]],
baselines: BaselineType = None,
target: TargetType = None,
additional_forward_args: Any = None,
return_convergence_delta: Literal[False] = False,
attribute_to_layer_input: bool = False,
custom_attribution_func: Union[None, Callable[..., Tuple[Tensor, ...]]] = None,
) -> Union[Tensor, Tuple[Tensor, ...]]:
...
@typing.overload
def attribute(
self,
inputs: Union[Tensor, Tuple[Tensor, ...]],
baselines: BaselineType = None,
target: TargetType = None,
additional_forward_args: Any = None,
*,
return_convergence_delta: Literal[True],
attribute_to_layer_input: bool = False,
custom_attribution_func: Union[None, Callable[..., Tuple[Tensor, ...]]] = None,
) -> Tuple[Union[Tensor, Tuple[Tensor, ...]], Tensor]:
...
[docs]
@log_usage()
def attribute(
self,
inputs: Union[Tensor, Tuple[Tensor, ...]],
baselines: BaselineType = None,
target: TargetType = None,
additional_forward_args: Any = None,
return_convergence_delta: bool = False,
attribute_to_layer_input: bool = False,
custom_attribution_func: Union[None, Callable[..., Tuple[Tensor, ...]]] = None,
) -> Union[
Tensor, Tuple[Tensor, ...], Tuple[Union[Tensor, Tuple[Tensor, ...]], Tensor]
]:
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.
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
target (int, tuple, Tensor, or list, optional): Output indices for
which gradients are computed (for classification cases,
this is usually the target class).
If the network returns a scalar value per example,
no target index is necessary.
For general 2D outputs, targets can be either:
- a single integer or a tensor containing a single
integer, which is applied to all input examples
- a list of integers or a 1D tensor, with length matching
the number of examples in inputs (dim 0). Each integer
is applied as the target for the corresponding example.
For outputs with > 2 dimensions, targets can be either:
- A single tuple, which contains #output_dims - 1
elements. This target index is applied to all examples.
- A list of tuples with length equal to the number of
examples in inputs (dim 0), and each tuple containing
#output_dims - 1 elements. Each tuple is applied as the
target for the corresponding example.
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
return_convergence_delta (bool, optional): Indicates whether to return
convergence delta or not. If `return_convergence_delta`
is set to True convergence delta will be returned in
a tuple following attributions.
Default: False
attribute_to_layer_input (bool, optional): Indicates whether to
compute the attribution with respect to the layer input
or output. If `attribute_to_layer_input` is set to True
then the attributions will be computed with respect to
layer input, otherwise it will be computed with respect
to layer output.
Note that currently it is assumed that either the input
or the output of internal layer, 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, ...]*):
Attribution score computed based on DeepLift's rescale rule with
respect to layer's inputs or outputs. Attributions will always be the
same size as the provided layer's inputs or outputs, depending on
whether we attribute to the inputs or outputs of the layer.
If the layer input / output is a single tensor, then
just a tensor is returned; if the layer input / output
has multiple tensors, then a corresponding tuple
of tensors is returned.
- **delta** (*Tensor*, returned if return_convergence_delta=True):
This is computed using the property that the total sum of
model(inputs) - model(baselines) must equal the
total sum of the attributions computed based on DeepLift's
rescale rule.
Delta is calculated per example, meaning that the number of
elements in returned delta tensor is equal to the number of
examples in input.
Note that the logic described for deltas is guaranteed
when the default logic for attribution computations is used,
meaning that the `custom_attribution_func=None`, otherwise
it is not guaranteed and depends on the specifics of the
`custom_attribution_func`.
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 = LayerDeepLift(net, net.conv4)
>>> input = torch.randn(1, 3, 32, 32, requires_grad=True)
>>> # Computes deeplift attribution scores for conv4 layer and class 3.
>>> attribution = dl.attribute(input, target=1)
"""
inputs = _format_tensor_into_tuples(inputs)
baselines = _format_baseline(baselines, inputs)
_validate_input(inputs, baselines)
baselines = _tensorize_baseline(inputs, baselines)
main_model_hooks = []
try:
main_model_hooks = self._hook_main_model()
self.model.apply(
lambda mod: self._register_hooks(
mod, attribute_to_layer_input=attribute_to_layer_input
)
)
additional_forward_args = _format_additional_forward_args(
additional_forward_args
)
expanded_target = _expand_target(
target, 2, expansion_type=ExpansionTypes.repeat
)
wrapped_forward_func = self._construct_forward_func(
self.model,
(inputs, baselines),
expanded_target,
additional_forward_args,
)
def chunk_output_fn(out: TensorOrTupleOfTensorsGeneric) -> Sequence:
if isinstance(out, Tensor):
return out.chunk(2)
return tuple(out_sub.chunk(2) for out_sub in out)
gradients, attrs = compute_layer_gradients_and_eval(
wrapped_forward_func,
self.layer,
inputs,
attribute_to_layer_input=attribute_to_layer_input,
output_fn=lambda out: chunk_output_fn(out),
)
attr_inputs = tuple(map(lambda attr: attr[0], attrs))
attr_baselines = tuple(map(lambda attr: attr[1], attrs))
gradients = tuple(map(lambda grad: grad[0], gradients))
if custom_attribution_func is None:
if self.multiplies_by_inputs:
attributions = tuple(
(input - baseline) * gradient
for input, baseline, gradient in zip(
attr_inputs, attr_baselines, gradients
)
)
else:
attributions = gradients
else:
attributions = _call_custom_attribution_func(
custom_attribution_func, gradients, attr_inputs, attr_baselines
)
finally:
# remove hooks from all activations
self._remove_hooks(main_model_hooks)
return _compute_conv_delta_and_format_attrs(
self,
return_convergence_delta,
attributions,
baselines,
inputs,
additional_forward_args,
target,
cast(Union[Literal[True], Literal[False]], len(attributions) > 1),
)
@property
def multiplies_by_inputs(self):
return self._multiply_by_inputs
[docs]
class LayerDeepLiftShap(LayerDeepLift, DeepLiftShap):
r"""
Extends LayerDeepLift and DeepLiftShap algorithms and approximates SHAP
values for given input `layer`.
For each input sample - baseline pair it computes DeepLift attributions
with respect to inputs or outputs of given `layer` 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 attributions are computed.
The size and dimensionality of the attributions
corresponds to the size and dimensionality of the layer's
input or output depending on whether we attribute to the
inputs or outputs of the layer.
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 LayerDeepLiftShap, if `multiply_by_inputs`
is set to True, final sensitivity scores are being
multiplied by
layer activations for inputs - layer activations for baselines
This flag applies only if `custom_attribution_func` is
set to None.
"""
LayerDeepLift.__init__(self, model, layer)
DeepLiftShap.__init__(self, model, multiply_by_inputs)
# Ignoring mypy error for inconsistent signature with DeepLiftShap
@typing.overload # type: ignore
def attribute(
self,
inputs: Union[Tensor, Tuple[Tensor, ...]],
baselines: Union[
Tensor, Tuple[Tensor, ...], Callable[..., Union[Tensor, Tuple[Tensor, ...]]]
],
target: TargetType = None,
additional_forward_args: Any = None,
return_convergence_delta: Literal[False] = False,
attribute_to_layer_input: bool = False,
custom_attribution_func: Union[None, Callable[..., Tuple[Tensor, ...]]] = None,
) -> Union[Tensor, Tuple[Tensor, ...]]:
...
@typing.overload
def attribute(
self,
inputs: Union[Tensor, Tuple[Tensor, ...]],
baselines: Union[
Tensor, Tuple[Tensor, ...], Callable[..., Union[Tensor, Tuple[Tensor, ...]]]
],
target: TargetType = None,
additional_forward_args: Any = None,
*,
return_convergence_delta: Literal[True],
attribute_to_layer_input: bool = False,
custom_attribution_func: Union[None, Callable[..., Tuple[Tensor, ...]]] = None,
) -> Tuple[Union[Tensor, Tuple[Tensor, ...]], Tensor]:
...
[docs]
@log_usage()
def attribute(
self,
inputs: Union[Tensor, Tuple[Tensor, ...]],
baselines: Union[
Tensor, Tuple[Tensor, ...], Callable[..., Union[Tensor, Tuple[Tensor, ...]]]
],
target: TargetType = None,
additional_forward_args: Any = None,
return_convergence_delta: bool = False,
attribute_to_layer_input: bool = False,
custom_attribution_func: Union[None, Callable[..., Tuple[Tensor, ...]]] = None,
) -> Union[
Tensor, Tuple[Tensor, ...], Tuple[Union[Tensor, Tuple[Tensor, ...]], Tensor]
]:
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.
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.
target (int, tuple, Tensor, or list, optional): Output indices for
which gradients are computed (for classification cases,
this is usually the target class).
If the network returns a scalar value per example,
no target index is necessary.
For general 2D outputs, targets can be either:
- a single integer or a tensor containing a single
integer, which is applied to all input examples
- a list of integers or a 1D tensor, with length matching
the number of examples in inputs (dim 0). Each integer
is applied as the target for the corresponding example.
For outputs with > 2 dimensions, targets can be either:
- A single tuple, which contains #output_dims - 1
elements. This target index is applied to all examples.
- A list of tuples with length equal to the number of
examples in inputs (dim 0), and each tuple containing
#output_dims - 1 elements. Each tuple is applied as the
target for the corresponding example.
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
return_convergence_delta (bool, optional): Indicates whether to return
convergence delta or not. If `return_convergence_delta`
is set to True convergence delta will be returned in
a tuple following attributions.
Default: False
attribute_to_layer_input (bool, optional): Indicates whether to
compute the attributions with respect to the layer input
or output. If `attribute_to_layer_input` is set to True
then the attributions will be computed with respect to
layer inputs, otherwise it will be computed with respect
to layer outputs.
Note that currently it assumes that both the inputs and
outputs of internal layers are single tensors.
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, ...]*):
Attribution score computed based on DeepLift's rescale rule
with respect to layer's inputs or outputs. Attributions
will always be the same size as the provided layer's inputs
or outputs, depending on whether we attribute to the inputs
or outputs of the layer.
Attributions are returned in a tuple based on whether
the layer inputs / outputs are contained in a tuple
from a forward hook. For standard modules, inputs of
a single tensor are usually wrapped in a tuple, while
outputs of a single tensor are not.
- **delta** (*Tensor*, returned if return_convergence_delta=True):
This is computed using the property that the
total sum of model(inputs) - model(baselines)
must be very close to the total sum of attributions
computed based on approximated SHAP values using
DeepLift's rescale rule.
Delta is calculated for each example input and baseline pair,
meaning that the number of elements in returned delta tensor
is equal to the
`number of examples in input` * `number of examples
in baseline`. The deltas are ordered in the first place by
input example, followed by the baseline.
Note that the logic described for deltas is guaranteed
when the default logic for attribution computations is used,
meaning that the `custom_attribution_func=None`, otherwise
it is not guaranteed and depends on the specifics of the
`custom_attribution_func`.
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 = LayerDeepLiftShap(net, net.conv4)
>>> input = torch.randn(2, 3, 32, 32, requires_grad=True)
>>> # Computes shap values using deeplift for class 3.
>>> attribution = dl.attribute(input, target=3)
"""
inputs = _format_tensor_into_tuples(inputs)
baselines = _format_callable_baseline(baselines, inputs)
assert isinstance(baselines[0], torch.Tensor) and baselines[0].shape[0] > 1, (
"Baselines distribution has to be provided in form of a torch.Tensor"
" with more than one example but found: {}."
" If baselines are provided in shape of scalars or with a single"
" baseline example, `LayerDeepLift`"
" approach can be used instead.".format(baselines[0])
)
# batch sizes
inp_bsz = inputs[0].shape[0]
base_bsz = baselines[0].shape[0]
(
exp_inp,
exp_base,
exp_target,
exp_addit_args,
) = DeepLiftShap._expand_inputs_baselines_targets(
self, baselines, inputs, target, additional_forward_args
)
attributions = LayerDeepLift.attribute.__wrapped__( # type: ignore
self,
exp_inp,
exp_base,
target=exp_target,
additional_forward_args=exp_addit_args,
return_convergence_delta=cast(
Literal[True, False], return_convergence_delta
),
attribute_to_layer_input=attribute_to_layer_input,
custom_attribution_func=custom_attribution_func,
)
if return_convergence_delta:
attributions, delta = attributions
if isinstance(attributions, tuple):
attributions = tuple(
DeepLiftShap._compute_mean_across_baselines(
self, inp_bsz, base_bsz, cast(Tensor, attrib)
)
for attrib in attributions
)
else:
attributions = DeepLiftShap._compute_mean_across_baselines(
self, inp_bsz, base_bsz, attributions
)
if return_convergence_delta:
return attributions, delta
else:
return attributions
@property
def multiplies_by_inputs(self):
return self._multiply_by_inputs
```