Develop a fake dequantized op for fixed-point quantization training framework.

paddle/fluid/operators/CMakeLists.txt

@@ -168,6 +168,8 @@ function(op_library TARGET)
         file(APPEND ${pybind_file} "USE_OP(relu);\n")
       elseif(${TARGET} STREQUAL "reduce")
         file(APPEND ${pybind_file} "USE_OP(reduce_sum);\n")
+      elseif(${TARGET} STREQUAL "fake_dequantize")
+        file(APPEND ${pybind_file} "USE_OP(fake_dequantize_max_abs);\n")
       else()
         file(APPEND ${pybind_file} "USE_OP(${TARGET});\n")
       endif()

paddle/fluid/operators/fake_dequantize_op.cc

@@ -0,0 +1,76 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserved.
+
+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/fluid/operators/fake_dequantize_op.h"
+#include <string>
+
+namespace paddle {
+namespace operators {
+
+class FakeDequantizeMaxAbsOp : public framework::OperatorWithKernel {
+ public:
+  FakeDequantizeMaxAbsOp(const std::string &type,
+                         const framework::VariableNameMap &inputs,
+                         const framework::VariableNameMap &outputs,
+                         const framework::AttributeMap &attrs)
+      : OperatorWithKernel(type, inputs, outputs, attrs) {}
+
+  void InferShape(framework::InferShapeContext *ctx) const override {
+    PADDLE_ENFORCE(ctx->HasInput("X"),
+                   "Input(X) of FakeDequantizeMaxAbsOp should not be null.");
+    PADDLE_ENFORCE(ctx->HasOutput("Out"),
+                   "Output(Out) of FakeDequantizeMaxAbsOp should not be null.");
+    ctx->SetOutputDim("Out", ctx->GetInputDim("X"));
+    ctx->ShareLoD("X", /*->*/ "Out");
+  }
+};
+
+class FakeDequantizeMaxAbsOpMaker : public framework::OpProtoAndCheckerMaker {
+ public:
+  void Make() override {
+    AddInput("X",
+             "(Tensor) The input with float-32/64 type is the "
+             "low precision tensor.");
+    AddOutput("Out",
+              "(Tensor) The output is the dequantized high "
+              "precision tensor.");
+    AddAttr<int>("num_bits",
+                 "(int) `num_bits` is the quantization level bits, "
+                 "such as 2, 5, 8.");
+    AddAttr<float>("scale",
+                   "(float) The maximum absolute value of low precision tensor."
+                   "It is usually calculated by the fake_quantize_max_abs_op.");
+    AddComment(R"DOC(
+FakeDequantizeMaxAbsOp operator.
+
+This calculation is an opposite operation of FakeQuantizeMaxAbsOp:
+
+$$Out = \frac{scale*X}{2^{num_bits} - 1}$$
+
+)DOC");
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle
+
+namespace ops = paddle::operators;
+using CPU = paddle::platform::CPUDeviceContext;
+
+REGISTER_OPERATOR(fake_dequantize_max_abs, ops::FakeDequantizeMaxAbsOp,
+                  ops::FakeDequantizeMaxAbsOpMaker,
+                  paddle::framework::EmptyGradOpMaker);
+REGISTER_OP_CPU_KERNEL(fake_dequantize_max_abs,
+                       ops::FakeDequantizeMaxAbsKernel<CPU, float>,
+                       ops::FakeDequantizeMaxAbsKernel<CPU, double>);

paddle/fluid/operators/fake_dequantize_op.cu

@@ -0,0 +1,21 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserved.
+
+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/fluid/operators/fake_dequantize_op.h"
+
+namespace ops = paddle::operators;
+using CUDA = paddle::platform::CUDADeviceContext;
+REGISTER_OP_CUDA_KERNEL(fake_dequantize_max_abs,
+                        ops::FakeDequantizeMaxAbsKernel<CUDA, float>,
+                        ops::FakeDequantizeMaxAbsKernel<CUDA, double>);

paddle/fluid/operators/fake_dequantize_op.h

@@ -0,0 +1,42 @@
+/* Copyright (c) 2016 PaddlePaddle Authors. All Rights Reserved.
+
+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/fluid/framework/eigen.h"
+#include "paddle/fluid/framework/op_registry.h"
+
+namespace paddle {
+namespace operators {
+template <typename DeviceContext, typename T>
+class FakeDequantizeMaxAbsKernel : public framework::OpKernel<T> {
+ public:
+  virtual void Compute(const framework::ExecutionContext& ctx) const {
+    auto* in = ctx.Input<framework::Tensor>("X");
+    auto* out = ctx.Output<framework::Tensor>("Out");
+    out->mutable_data<T>(in->place());
+
+    int num_bits = ctx.Attr<int>("num_bits");
+    T scale = static_cast<T>(ctx.Attr<float>("scale"));
+    int range = std::pow(2, num_bits) - 1;
+
+    auto eigen_out = framework::EigenVector<T>::Flatten(*out);
+    auto eigen_in = framework::EigenVector<T>::Flatten(*in);
+    auto& dev = *ctx.template device_context<DeviceContext>().eigen_device();
+    eigen_out.device(dev) = (scale / range) * eigen_in;
+  }
+};
+
+}  // namespace operators
+}  // namespace paddle

python/paddle/fluid/tests/unittests/test_fake_dequantize_op.py

@@ -0,0 +1,60 @@
+#   Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.
+#
+# 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.
+
+import unittest
+import numpy as np
+import math
+from op_test import OpTest
+
+
+def quantize_max_abs(x, num_bits):
+    range = math.pow(2, num_bits) - 1
+    scale = np.max(np.abs(x).flatten())
+    y = np.round(x / scale * range)
+    return y, scale
+
+
+def dequantize_max_abs(x, num_bits, scale):
+    range = math.pow(2, num_bits) - 1
+    y = (scale / range) * x
+    return y
+
+
+class TestFakeDequantizeMaxAbsOp(OpTest):
+    def set_args(self):
+        self.num_bits = 8
+
+    def setUp(self):
+        self.set_args()
+        self.op_type = "fake_dequantize_max_abs"
+        x = np.random.randn(31, 65).astype("float32")
+        yq, scale = quantize_max_abs(x, self.num_bits)
+        print 'scale ', scale
+        ydq = dequantize_max_abs(yq, self.num_bits, scale)
+
+        self.inputs = {'X': yq}
+        self.attrs = {'num_bits': self.num_bits, 'scale': float(scale)}
+        self.outputs = {'Out': ydq}
+
+    def test_check_output(self):
+        self.check_output()
+
+
+class TestFakeDequantizeMaxAbsOp5Bits(OpTest):
+    def set_args(self):
+        self.num_bits = 5
+
+
+if __name__ == "__main__":
+    unittest.main()