Add cpp folder for C++ frontend examples

.gitignore

@@ -2,3 +2,5 @@ dcgan/data
 data
 *.pyc
 OpenNMT/data
+cpp/mnist/build
+cpp/dcgan/build

cpp/.clang-format

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+...

cpp/dcgan/CMakeLists.txt

@@ -0,0 +1,20 @@
+cmake_minimum_required(VERSION 3.0 FATAL_ERROR)
+project(dcgan)
+
+find_package(Torch REQUIRED)
+
+option(DOWNLOAD_MNIST "Download the MNIST dataset from the internet" ON)
+if (DOWNLOAD_MNIST)
+  message(STATUS "Downloading MNIST dataset")
+  execute_process(
+    COMMAND python ${CMAKE_CURRENT_LIST_DIR}/../tools/download_mnist.py
+      -d ${CMAKE_BINARY_DIR}/data
+    ERROR_VARIABLE DOWNLOAD_ERROR)
+  if (DOWNLOAD_ERROR)
+    message(FATAL_ERROR "Error downloading MNIST dataset: ${DOWNLOAD_ERROR}")
+  endif()
+endif()
+
+add_executable(dcgan dcgan.cpp)
+target_link_libraries(dcgan "${TORCH_LIBRARIES}")
+set_property(TARGET dcgan PROPERTY CXX_STANDARD 11)

cpp/dcgan/README.md

@@ -0,0 +1,56 @@
+# DCGAN Example with the PyTorch C++ Frontend
+
+This folder contains an example of training a DCGAN to generate MNIST digits
+with the PyTorch C++ frontend.
+
+The entire training code is contained in `dcgan.cpp`.
+
+To build the code, run the following commands from your terminal:
+
+```shell
+$ cd dcgan
+$ mkdir build
+$ cd build
+$ cmake -DCMAKE_PREFIX_PATH=/path/to/libtorch ..
+$ make
+```
+
+where `/path/to/libtorch` should be the path to the unzipped *LibTorch*
+distribution, which you can get from the [PyTorch
+homepage](https://pytorch.org/get-started/locally/).
+
+Execute the compiled binary to train the model:
+
+```shell
+$ ./dcgan
+[ 1/30][200/938] D_loss: 0.4953 | G_loss: 4.0195
+-> checkpoint 1
+[ 1/30][400/938] D_loss: 0.3610 | G_loss: 4.8148
+-> checkpoint 2
+[ 1/30][600/938] D_loss: 0.4072 | G_loss: 4.36760
+-> checkpoint 3
+[ 1/30][800/938] D_loss: 0.4444 | G_loss: 4.0250
+-> checkpoint 4
+[ 2/30][200/938] D_loss: 0.3761 | G_loss: 3.8790
+-> checkpoint 5
+[ 2/30][400/938] D_loss: 0.3977 | G_loss: 3.3315
+-> checkpoint 6
+[ 2/30][600/938] D_loss: 0.3815 | G_loss: 3.5696
+-> checkpoint 7
+[ 2/30][800/938] D_loss: 0.4039 | G_loss: 3.2759
+-> checkpoint 8
+[ 3/30][200/938] D_loss: 0.4236 | G_loss: 4.5132
+-> checkpoint 9
+[ 3/30][400/938] D_loss: 0.3645 | G_loss: 3.9759
+-> checkpoint 10
+...
+```
+
+The training script periodically generates image samples. Use the
+`display_samples.py` script situated in this folder to generate a plot image.
+For example:
+
+```shell
+$ python display_samples.py -i dcgan-sample-10.png
+Saved out.png
+```

cpp/dcgan/dcgan.cpp

@@ -0,0 +1,187 @@
+#include <torch/torch.h>
+
+#include <cmath>
+#include <cstdio>
+#include <iostream>
+
+// The size of the noise vector fed to the generator.
+const int64_t kNoiseSize = 100;
+
+// The batch size for training.
+const int64_t kBatchSize = 64;
+
+// The number of epochs to train.
+const int64_t kNumberOfEpochs = 30;
+
+// Where to find the MNIST dataset.
+const char* kDataFolder = "./data";
+
+// After how many batches to create a new checkpoint periodically.
+const int64_t kCheckpointEvery = 200;
+
+// How many images to sample at every checkpoint.
+const int64_t kNumberOfSamplesPerCheckpoint = 10;
+
+// Set to `true` to restore models and optimizers from previously saved
+// checkpoints.
+const bool kRestoreFromCheckpoint = false;
+
+// After how many batches to log a new update with the loss value.
+const int64_t kLogInterval = 10;
+
+using namespace torch;
+
+int main(int argc, const char* argv[]) {
+  torch::manual_seed(1);
+
+  // Create the device we pass around based on whether CUDA is available.
+  torch::Device device(torch::kCPU);
+  if (torch::cuda::is_available()) {
+    std::cout << "CUDA is available! Training on GPU." << std::endl;
+    device = torch::Device(torch::kCUDA);
+  }
+
+  nn::Sequential generator(
+      // Layer 1
+      nn::Conv2d(nn::Conv2dOptions(kNoiseSize, 256, 4)
+                     .with_bias(false)
+                     .transposed(true)),
+      nn::BatchNorm(256),
+      nn::Functional(torch::relu),
+      // Layer 2
+      nn::Conv2d(nn::Conv2dOptions(256, 128, 3)
+                     .stride(2)
+                     .padding(1)
+                     .with_bias(false)
+                     .transposed(true)),
+      nn::BatchNorm(128),
+      nn::Functional(torch::relu),
+      // Layer 3
+      nn::Conv2d(nn::Conv2dOptions(128, 64, 4)
+                     .stride(2)
+                     .padding(1)
+                     .with_bias(false)
+                     .transposed(true)),
+      nn::BatchNorm(64),
+      nn::Functional(torch::relu),
+      // Layer 4
+      nn::Conv2d(nn::Conv2dOptions(64, 1, 4)
+                     .stride(2)
+                     .padding(1)
+                     .with_bias(false)
+                     .transposed(true)),
+      nn::Functional(torch::tanh));
+  generator->to(device);
+
+  nn::Sequential discriminator(
+      // Layer 1
+      nn::Conv2d(
+          nn::Conv2dOptions(1, 64, 4).stride(2).padding(1).with_bias(false)),
+      nn::Functional(torch::leaky_relu, 0.2),
+      // Layer 2
+      nn::Conv2d(
+          nn::Conv2dOptions(64, 128, 4).stride(2).padding(1).with_bias(false)),
+      nn::BatchNorm(128),
+      nn::Functional(torch::leaky_relu, 0.2),
+      // Layer 3
+      nn::Conv2d(
+          nn::Conv2dOptions(128, 256, 4).stride(2).padding(1).with_bias(false)),
+      nn::BatchNorm(256),
+      nn::Functional(torch::leaky_relu, 0.2),
+      // Layer 4
+      nn::Conv2d(
+          nn::Conv2dOptions(256, 1, 3).stride(1).padding(0).with_bias(false)),
+      nn::Functional(torch::sigmoid));
+  discriminator->to(device);
+
+  // Assume the MNIST dataset is available under `kDataFolder`;
+  auto dataset = torch::data::datasets::MNIST(kDataFolder)
+                     .map(torch::data::transforms::Normalize<>(0.5, 0.5))
+                     .map(torch::data::transforms::Stack<>());
+  const int64_t batches_per_epoch =
+      std::ceil(dataset.size().value() / static_cast<double>(kBatchSize));
+
+  auto data_loader = torch::data::make_data_loader(
+      std::move(dataset),
+      torch::data::DataLoaderOptions().batch_size(kBatchSize).workers(2));
+
+  torch::optim::Adam generator_optimizer(
+      generator->parameters(), torch::optim::AdamOptions(2e-4).beta1(0.5));
+  torch::optim::Adam discriminator_optimizer(
+      discriminator->parameters(), torch::optim::AdamOptions(2e-4).beta1(0.5));
+
+  if (kRestoreFromCheckpoint) {
+    torch::load(generator, "generator-checkpoint.pt");
+    torch::load(generator_optimizer, "generator-optimizer-checkpoint.pt");
+    torch::load(discriminator, "discriminator-checkpoint.pt");
+    torch::load(
+        discriminator_optimizer, "discriminator-optimizer-checkpoint.pt");
+  }
+
+  int64_t checkpoint_counter = 1;
+  for (int64_t epoch = 1; epoch <= kNumberOfEpochs; ++epoch) {
+    int64_t batch_index = 0;
+    for (torch::data::Example<>& batch : *data_loader) {
+      // Train discriminator with real images.
+      discriminator->zero_grad();
+      torch::Tensor real_images = batch.data.to(device);
+      torch::Tensor real_labels =
+          torch::empty(batch.data.size(0), device).uniform_(0.8, 1.0);
+      torch::Tensor real_output = discriminator->forward(real_images);
+      torch::Tensor d_loss_real =
+          torch::binary_cross_entropy(real_output, real_labels);
+      d_loss_real.backward();
+
+      // Train discriminator with fake images.
+      torch::Tensor noise =
+          torch::randn({batch.data.size(0), kNoiseSize, 1, 1}, device);
+      torch::Tensor fake_images = generator->forward(noise);
+      torch::Tensor fake_labels = torch::zeros(batch.data.size(0), device);
+      torch::Tensor fake_output = discriminator->forward(fake_images.detach());
+      torch::Tensor d_loss_fake =
+          torch::binary_cross_entropy(fake_output, fake_labels);
+      d_loss_fake.backward();
+
+      torch::Tensor d_loss = d_loss_real + d_loss_fake;
+      discriminator_optimizer.step();
+
+      // Train generator.
+      generator->zero_grad();
+      fake_labels.fill_(1);
+      fake_output = discriminator->forward(fake_images);
+      torch::Tensor g_loss =
+          torch::binary_cross_entropy(fake_output, fake_labels);
+      g_loss.backward();
+      generator_optimizer.step();
+
+      if (batch_index % kLogInterval == 0) {
+        std::printf(
+            "\r[%2ld/%2ld][%3ld/%3ld] D_loss: %.4f | G_loss: %.4f",
+            epoch,
+            kNumberOfEpochs,
+            ++batch_index,
+            batches_per_epoch,
+            d_loss.item<float>(),
+            g_loss.item<float>());
+      }
+
+      if (batch_index % kCheckpointEvery == 0) {
+        // Checkpoint the model and optimizer state.
+        torch::save(generator, "generator-checkpoint.pt");
+        torch::save(generator_optimizer, "generator-optimizer-checkpoint.pt");
+        torch::save(discriminator, "discriminator-checkpoint.pt");
+        torch::save(
+            discriminator_optimizer, "discriminator-optimizer-checkpoint.pt");
+        // Sample the generator and save the images.
+        torch::Tensor samples = generator->forward(torch::randn(
+            {kNumberOfSamplesPerCheckpoint, kNoiseSize, 1, 1}, device));
+        torch::save(
+            (samples + 1.0) / 2.0,
+            torch::str("dcgan-sample-", checkpoint_counter, ".pt"));
+        std::cout << "\n-> checkpoint " << ++checkpoint_counter << '\n';
+      }
+    }
+  }
+
+  std::cout << "Training complete!" << std::endl;
+}

cpp/dcgan/display_samples.py

@@ -0,0 +1,28 @@
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import argparse
+
+import matplotlib.pyplot as plt
+import torch
+
+
+parser = argparse.ArgumentParser()
+parser.add_argument("-i", "--sample-file", required=True)
+parser.add_argument("-o", "--out-file", default="out.png")
+parser.add_argument("-d", "--dimension", type=int, default=3)
+options = parser.parse_args()
+
+module = torch.jit.load(options.sample_file)
+images = list(module.parameters())[0]
+
+for index in range(options.dimension * options.dimension):
+    image = images[index].detach().cpu().reshape(28, 28).mul(255).to(torch.uint8)
+    array = image.numpy()
+    axis = plt.subplot(options.dimension, options.dimension, 1 + index)
+    plt.imshow(array, cmap="gray")
+    axis.get_xaxis().set_visible(False)
+    axis.get_yaxis().set_visible(False)
+
+plt.savefig(options.out_file)
+print("Saved ", options.out_file)