add sparsity modules

examples/movement-pruning/emmental/modules/masked_nn.py

@@ -0,0 +1,107 @@
+# coding=utf-8
+# Copyright 2020-present, the HuggingFace Inc. team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+Masked Linear module: A fully connected layer that computes an adaptive binary mask on the fly.
+The mask (binary or not) is computed at each forward pass and multiplied against
+the weight matrix to prune a portion of the weights.
+The pruned weight matrix is then multiplied against the inputs (and if necessary, the bias is added).
+"""
+
+import torch
+from torch import nn
+from torch.nn import functional as F
+from torch.nn import init
+
+import math
+
+from .binarizer import ThresholdBinarizer, TopKBinarizer, MagnitudeBinarizer
+
+
+class MaskedLinear(nn.Linear):
+    """
+    Fully Connected layer with on the fly adaptive mask.
+    If needed, a score matrix is created to store the importance of each associated weight.
+    """
+
+    def __init__(
+        self,
+        in_features: int,
+        out_features: int,
+        bias: bool = True,
+        mask_init: str = "constant",
+        mask_scale: float = 0.0,
+        pruning_method: str = "topK",
+    ):
+        """
+        Args:
+            in_features (`int`)
+                Size of each input sample
+            out_features (`int`)
+                Size of each output sample
+            bias (`bool`)
+                If set to ``False``, the layer will not learn an additive bias.
+                Default: ``True``
+            mask_init (`str`)
+                The initialization method for the score matrix if a score matrix is needed.
+                Choices: ["constant", "uniform", "kaiming"]
+                Default: ``constant``
+            mask_scale (`float`)
+                The initialization parameter for the chosen initialization method `mask_init`.
+                Default: ``0.``
+            pruning_method (`str`)
+                Method to compute the mask.
+                Choices: ["topK", "threshold", "sigmoied_threshold", "magnitude", "l0"]
+                Default: ``topK``
+        """
+        super(MaskedLinear, self).__init__(in_features=in_features, out_features=out_features, bias=bias)
+        assert pruning_method in ["topK", "threshold", "sigmoied_threshold", "magnitude", "l0"]
+        self.pruning_method = pruning_method
+
+        if self.pruning_method in ["topK", "threshold", "sigmoied_threshold", "l0"]:
+            self.mask_scale = mask_scale
+            self.mask_init = mask_init
+            self.mask_scores = nn.Parameter(torch.Tensor(self.weight.size()))
+            self.init_mask()
+
+    def init_mask(self):
+        if self.mask_init == "constant":
+            init.constant_(self.mask_scores, val=self.mask_scale)
+        elif self.mask_init == "uniform":
+            init.uniform_(self.mask_scores, a=-self.mask_scale, b=self.mask_scale)
+        elif self.mask_init == "kaiming":
+            init.kaiming_uniform_(self.mask_scores, a=math.sqrt(5))
+
+    def forward(self, input: torch.tensor, threshold: float):
+        # Get the mask
+        if self.pruning_method == "topK":
+            mask = TopKBinarizer.apply(self.mask_scores, threshold)
+        elif self.pruning_method in ["threshold", "sigmoied_threshold"]:
+            sig = "sigmoied" in self.pruning_method
+            mask = ThresholdBinarizer.apply(self.mask_scores, threshold, sig)
+        elif self.pruning_method == "magnitude":
+            mask = MagnitudeBinarizer.apply(self.weight, threshold)
+        elif self.pruning_method == "l0":
+            l, r, b = -0.1, 1.1, 2 / 3
+            if self.training:
+                u = torch.zeros_like(self.mask_scores).uniform_().clamp(0.0001, 0.9999)
+                s = torch.sigmoid((u.log() - (1 - u).log() + self.mask_scores) / b)
+            else:
+                s = torch.sigmoid(self.mask_scores)
+            s_bar = s * (r - l) + l
+            mask = s_bar.clamp(min=0.0, max=1.0)
+        # Mask weights with computed mask
+        weight_thresholded = mask * self.weight
+        # Compute output (linear layer) with masked weights
+        return F.linear(input, weight_thresholded, self.bias)