FEAT: Adding SGD, Adam, and RMSProp optimizers

- Moved zeroGrad to be part of Optimizer class
- Renamed perceptron.cpp to xor.cpp
- Modified xor example to run with SGD, Adam, or RMSProp optimizers

Author: pavanky

CMakeLists.txt

@@ -19,6 +19,7 @@ target_sources(afml
   src/nn/Modules/Module.cpp
   src/nn/Modules/Dropout.cpp
   src/nn/Init.cpp
+  src/optim/Optimizers.cpp
   )
 
 target_include_directories(afml

examples/CMakeLists.txt

@@ -13,6 +13,6 @@ endfunction(build_example)
 # build_example(Activations.cpp)
 # build_example(FFNet.cpp)
 # build_example(Node.cpp)
-build_example(perceptron.cpp)
+build_example(xor.cpp)
 # build_example(Weights.cpp)
 build_example(autograd.cpp)

examples/perceptron.cpp renamed to examples/xor.cpp

@@ -9,16 +9,29 @@
 
 #include <af/autograd.h>
 #include <af/nn.h>
+#include <af/optim.h>
+
+#include <string>
+#include <memory>
 
 using namespace af;
 using namespace af::nn;
 using namespace af::autograd;
 
-int main()
+int main(int argc, const char **args)
 {
+    int optim_mode = 0;
+    std::string optimizer_arg = std::string(args[1]);
+    if (optimizer_arg == "--adam") {
+        optim_mode = 1;
+    } else if (optimizer_arg == "--rmsprop") {
+        optim_mode = 2;
+    }
+
     const int inputSize  = 2;
     const int outputSize = 1;
-    const double lr = 0.1;
+    const double lr = 0.01;
+    const double mu = 0.1;
     const int numSamples = 4;
 
     float hInput[] = {1, 1,
@@ -34,24 +47,35 @@ int main()
     auto in = af::array(inputSize, numSamples, hInput);
     auto out = af::array(outputSize, numSamples, hOutput);
 
-    nn::Sequential perceptron;
+    nn::Sequential model;
 
-    perceptron.add(nn::Linear(inputSize, outputSize));
-    perceptron.add(nn::Sigmoid());
+    model.add(nn::Linear(inputSize, outputSize));
+    model.add(nn::Sigmoid());
 
     auto loss = nn::MeanSquaredError();
 
+    std::unique_ptr<optim::Optimizer> optim;
+
+    if (optimizer_arg == "--rmsprop") {
+        optim = std::unique_ptr<optim::Optimizer>(new optim::RMSPropOptimizer(model.parameters(), lr));
+    } else if (optimizer_arg == "--adam") {
+        optim = std::unique_ptr<optim::Optimizer>(new optim::AdamOptimizer(model.parameters(), lr));
+    } else {
+        optim = std::unique_ptr<optim::Optimizer>(new optim::SGDOptimizer(model.parameters(), lr, mu));
+    }
+
     Variable result, l;
     for (int i = 0; i < 1000; i++) {
         for (int j = 0; j < numSamples; j++) {
-            perceptron.train();
-            perceptron.zeroGrad();
+
+            model.train();
+            optim->zeroGrad();
 
             af::array in_j = in(af::span, j);
             af::array out_j = out(af::span, j);
 
             // Forward propagation
-            result = perceptron(nn::input(in_j));
+            result = model(nn::input(in_j));
 
             // Calculate loss
             l = loss(result, nn::noGrad(out_j));
@@ -60,18 +84,14 @@ int main()
             l.backward();
 
             // Update parameters
-            // TODO: Should use optimizer
-            for (auto &param : perceptron.parameters()) {
-                param.array() -= lr * param.grad().array();
-                param.array().eval();
-            }
+            optim->update();
         }
 
         if ((i + 1) % 100 == 0) {
-            perceptron.eval();
+            model.eval();
 
             // Forward propagation
-            result = perceptron(nn::input(in));
+            result = model(nn::input(in));
 
             // Calculate loss
             // TODO: Use loss function

include/af/nn/Modules/Module.hpp

@@ -35,8 +35,6 @@ namespace af
 
             std::vector<autograd::Variable> parameters();
 
-            void zeroGrad();
-
             void train();
 
             void eval();

include/af/optim.h

@@ -0,0 +1,9 @@
+/*******************************************************
+ * Copyright (c) 2017, ArrayFire
+ * All rights reserved.
+ *
+ * This file is distributed under 3-clause BSD license.
+ * The complete license agreement can be obtained at:
+ * http://arrayfire.com/licenses/BSD-3-Clause
+ ********************************************************/
+#include <af/optim/Optimizers.hpp>

include/af/optim/Optimizers.hpp

@@ -0,0 +1,90 @@
+/*******************************************************
+ * Copyright (c) 2017, ArrayFire
+ * All rights reserved.
+ *
+ * This file is distributed under 3-clause BSD license.
+ * The complete license agreement can be obtained at:
+ * http://arrayfire.com/licenses/BSD-3-Clause
+ ********************************************************/
+
+#pragma once
+
+#include <af/autograd/Variable.hpp>
+#include <arrayfire.h>
+
+#include <vector>
+
+namespace af
+{
+    namespace optim
+    {
+
+        class Optimizer
+        {
+        protected:
+            std::vector<autograd::Variable> m_parameters;
+        public:
+
+            Optimizer(const std::vector<autograd::Variable> &parameters);
+
+            virtual void update() = 0;
+
+            void zeroGrad();
+        };
+
+        class SGDOptimizer : public Optimizer
+        {
+            bool m_use_nesterov;
+            double m_lr;
+            double m_mu;
+            double m_wd;
+            std::vector<af::array> m_velocities;
+        public:
+            SGDOptimizer(const std::vector<autograd::Variable> &parameters,
+                         double learning_rate, double momentum = 0,
+                         double weight_decay = 0,
+                         bool use_nesterov = false);
+            void update();
+        };
+
+        class AdamOptimizer : public Optimizer
+        {
+            double m_lr;
+            double m_beta1;
+            double m_beta2;
+            double m_eps;
+            double m_wd;
+            int m_count;
+            std::vector<af::array> m_biased_first;
+            std::vector<af::array> m_biased_second;
+        public:
+            AdamOptimizer(const std::vector<autograd::Variable> &parameters,
+                          double learning_rate,
+                          double beta1 = 0.9,
+                          double beta2 = 0.999,
+                          double epsilon = 1E-8,
+                          double weight_decay = 0);
+            void update();
+        };
+
+        class RMSPropOptimizer : public Optimizer
+        {
+            bool m_use_first;
+            double m_lr;
+            double m_rho;
+            double m_eps;
+            double m_wd;
+            std::vector<af::array> m_first;
+            std::vector<af::array> m_second;
+        public:
+            RMSPropOptimizer(const std::vector<autograd::Variable> &parameters,
+                             double learning_rate,
+                             double rho = 0.99,
+                             double epsilon = 1E-8,
+                             double weight_decay = 0,
+                             bool use_first = false);
+            void update();
+        };
+
+    }
+}

src/nn/Modules/Module.cpp

@@ -54,13 +54,6 @@ namespace af
             return m_parameters;
         }
 
-        void Module::zeroGrad()
-        {
-            for (auto &parameter : m_parameters) {
-                parameter.zeroGrad();
-            }
-        }
-
         Variable Module::operator()(const Variable &input)
         {
             return this->forward(input);