Adding the squared L2 norm operator for L2 regularization (#5030)

* Adding the L2 loss operator for L2 regularization
* Renaming l2_loss op to squared_l2_norm_op
* Addressing code review feedback

paddle/operators/squared_l2_norm_op.cc

+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+   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. */
+
+#include "paddle/operators/squared_l2_norm_op.h"
+
+namespace paddle {
+namespace operators {
+
+using framework::Tensor;
+
+class SquaredL2NormOp : public framework::OperatorWithKernel {
+ public:
+  using framework::OperatorWithKernel::OperatorWithKernel;
+
+  void InferShape(framework::InferShapeContext* ctx) const override {
+    PADDLE_ENFORCE(ctx->HasInput("X"), "Input(X) should be not null.");
+    PADDLE_ENFORCE(ctx->HasOutput("Out"), "Output(Out) should be not null.");
+
+    ctx->SetOutputDim("Out", {1});
+  }
+};
+
+class SquaredL2NormGradOp : public framework::OperatorWithKernel {
+ public:
+  using framework::OperatorWithKernel::OperatorWithKernel;
+
+  void InferShape(framework::InferShapeContext* ctx) const override {
+    PADDLE_ENFORCE(ctx->HasInput("X"), "Input(X) should be not null.");
+    PADDLE_ENFORCE(ctx->HasInput(framework::GradVarName("Out")),
+                   "Input(Out@GRAD) should be not null.");
+    PADDLE_ENFORCE(ctx->HasOutput(framework::GradVarName("X")),
+                   "Output(X@GRAD) should be not null.");
+
+    ctx->SetOutputDim(framework::GradVarName("X"), ctx->GetInputDim("X"));
+  }
+};
+
+class SquaredL2NormOpMaker : public framework::OpProtoAndCheckerMaker {
+ public:
+  SquaredL2NormOpMaker(framework::OpProto* proto,
+                       framework::OpAttrChecker* op_checker)
+      : framework::OpProtoAndCheckerMaker(proto, op_checker) {
+    AddInput("X", "(Tensor) The input of squared_l2_norm op.");
+    AddOutput("Out", "(Float) The output of squared_l2_norm op.");
+    AddComment(R"DOC(
+SquaredL2Norm Operator.
+
+Computes the squared L2 norm of a tensor.
+
+Out = sum (X ** 2)
+
+)DOC");
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle
+
+namespace ops = paddle::operators;
+REGISTER_OP(squared_l2_norm, ops::SquaredL2NormOp, ops::SquaredL2NormOpMaker,
+            squared_l2_norm_grad, ops::SquaredL2NormGradOp);
+REGISTER_OP_CPU_KERNEL(
+    squared_l2_norm,
+    ops::SquaredL2NormKernel<paddle::platform::CPUPlace, float>);
+REGISTER_OP_CPU_KERNEL(
+    squared_l2_norm_grad,
+    ops::SquaredL2NormGradKernel<paddle::platform::CPUPlace, float>);

paddle/operators/squared_l2_norm_op.cu

+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+   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. */
+
+#define EIGEN_USE_GPU
+#include "paddle/operators/squared_l2_norm_op.h"
+
+namespace ops = paddle::operators;
+REGISTER_OP_GPU_KERNEL(
+    squared_l2_norm,
+    ops::SquaredL2NormKernel<paddle::platform::GPUPlace, float>);
+REGISTER_OP_GPU_KERNEL(
+    squared_l2_norm_grad,
+    ops::SquaredL2NormGradKernel<paddle::platform::GPUPlace, float>);

paddle/operators/squared_l2_norm_op.h

+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserve.
+
+   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. */
+
+#pragma once
+#include "paddle/framework/eigen.h"
+#include "paddle/framework/op_registry.h"
+
+namespace paddle {
+namespace operators {
+
+// Out = sum(square(X))
+template <typename Place, typename T>
+class SquaredL2NormKernel : public framework::OpKernel<T> {
+ public:
+  void Compute(const framework::ExecutionContext &context) const override {
+    const framework::Tensor *X = context.Input<framework::Tensor>("X");
+    framework::Tensor *Out = context.Output<framework::Tensor>("Out");
+    Out->mutable_data<T>(context.GetPlace());
+
+    auto x = framework::EigenVector<T>::Flatten(*X);
+    auto out = framework::EigenVector<T>::Flatten(*Out);
+    auto place = context.GetEigenDevice<Place>();
+
+    out.device(place) = x.square().sum();
+  }
+};
+
+// dX = X
+template <typename Place, typename T>
+class SquaredL2NormGradKernel : public framework::OpKernel<T> {
+ public:
+  void Compute(const framework::ExecutionContext &context) const override {
+    const framework::Tensor *X = context.Input<framework::Tensor>("X");
+    const framework::Tensor *dOut =
+        context.Input<framework::Tensor>(framework::GradVarName("Out"));
+    PADDLE_ENFORCE(dOut->numel() == 1,
+                   "Squared L2 Norm Gradient should be scalar");
+    framework::Tensor *dX =
+        context.Output<framework::Tensor>(framework::GradVarName("X"));
+    dX->mutable_data<T>(context.GetPlace());
+
+    auto x = framework::EigenVector<T>::Flatten(*X);
+    auto dout = framework::EigenVector<T>::Flatten(*dOut);
+    auto dx = framework::EigenVector<T>::Flatten(*dX);
+    auto place = context.GetEigenDevice<Place>();
+
+    Eigen::DSizes<int, 1> x_dsize(X->numel());
+    dx.device(place) = (dout.broadcast(x_dsize) * x) * static_cast<T>(2.0);
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle

python/paddle/v2/framework/tests/test_squared_l2_norm_op.py

+import numpy as np
+import unittest
+from numpy import linalg as LA
+from op_test import OpTest
+
+
+class TestL2LossOp(OpTest):
+    """Test squared_l2_norm
+    """
+
+    def setUp(self):
+        self.op_type = "squared_l2_norm"
+        self.max_relative_error = 0.05
+
+        X = np.random.uniform(-1, 1, (13, 19)).astype("float32")
+        X[np.abs(X) < self.max_relative_error] = 0.1
+        self.inputs = {'X': X}
+        self.outputs = {'Out': np.square(LA.norm(X))}
+
+    def test_check_output(self):
+        self.check_output()
+
+    def test_check_grad(self):
+        self.check_grad(
+            ['X'], 'Out', max_relative_error=self.max_relative_error)
+
+
+if __name__ == "__main__":
+    unittest.main()