add functions loading MNIST dataset

.gitignore

@@ -39,3 +39,4 @@ build
 
 # Examples
 examples/*/*.gz
+examples/mnist/*ubyte

examples/mnist/Makefile

@@ -2,9 +2,12 @@
 
 all: download
 
-download: train-images-idx3-ubyte.gz train-labels-idx1-ubyte.gz t10k-images-idx3-ubyte.gz t10k-labels-idx3-ubyte.gz
+download: train-images-idx3-ubyte train-labels-idx1-ubyte t10k-images-idx3-ubyte t10k-labels-idx1-ubyte
 
-%.gz:
+%-ubyte: %-ubyte.gz
+	gzip -d < $^ > $@
+
+%-ubyte.gz:
 	wget http://yann.lecun.com/exdb/mnist/$*.gz -O $@
 
 clean:

src/mnist.h

@@ -0,0 +1,94 @@
+#pragma once
+
+#include <string>
+#include <iostream>
+#include <fstream>
+#include <vector>
+
+namespace datasets {
+namespace mnist {
+
+typedef unsigned char uchar;
+
+auto reverseInt = [](int i) {
+  unsigned char c1, c2, c3, c4;
+  c1 = i & 255, c2 = (i >> 8) & 255, c3 = (i >> 16) & 255, c4 = (i >> 24) & 255;
+  return ((int)c1 << 24) + ((int)c2 << 16) + ((int)c3 << 8) + c4;
+};
+
+std::vector<std::vector<float>> ReadImages(const std::string& full_path) {
+  std::ifstream file(full_path);
+
+  if (! file.is_open())
+    throw std::runtime_error("Cannot open file `" + full_path + "`!");
+
+  int magic_number = 0, n_rows = 0, n_cols = 0;
+
+  file.read((char *)&magic_number, sizeof(magic_number));
+  magic_number = reverseInt(magic_number);
+
+  if (magic_number != 2051)
+    throw std::runtime_error("Invalid MNIST image file!");
+
+  int number_of_images = 0;
+  file.read((char *)&number_of_images, sizeof(number_of_images)), number_of_images = reverseInt(number_of_images);
+  file.read((char *)&n_rows, sizeof(n_rows)), n_rows = reverseInt(n_rows);
+  file.read((char *)&n_cols, sizeof(n_cols)), n_cols = reverseInt(n_cols);
+
+  int image_size = n_rows * n_cols;
+  std::vector<std::vector<float>> _dataset(number_of_images, std::vector<float>(image_size));
+  unsigned char pixel = 0;
+
+  for (int i = 0; i < number_of_images; i++) {
+    for (int j = 0; j < image_size; j++) {
+      file.read((char*)&pixel, sizeof(pixel));
+      _dataset[i][j] = pixel / 255.0f;
+    }
+  }
+  return _dataset;
+}
+
+std::vector<int> ReadLabels(const std::string& full_path) {
+  std::ifstream file(full_path);
+
+  if (! file.is_open())
+    throw std::runtime_error("Cannot open file `" + full_path + "`!");
+
+  int magic_number = 0;
+  file.read((char *)&magic_number, sizeof(magic_number));
+  magic_number = reverseInt(magic_number);
+
+  if (magic_number != 2049)
+    throw std::runtime_error("Invalid MNIST label file!");
+
+  int number_of_labels = 0;
+  file.read((char *)&number_of_labels, sizeof(number_of_labels)), number_of_labels = reverseInt(number_of_labels);
+
+  std::vector<int> _dataset(number_of_labels);
+  for (int i = 0; i < number_of_labels; i++) {
+    file.read((char*)&_dataset[i], 1);
+  }
+
+  return _dataset;
+}
+
+} // namespace mnist
+} // namespace datasets
+
+
+//int main(int argc, const char *argv[]) {
+  //auto images = datasets::mnist::ReadImages("t10k-images-idx3-ubyte");
+  //auto labels = datasets::mnist::ReadLabels("t10k-labels-idx1-ubyte");
+
+  //std::cout
+    //<< "Number of images: " << images.size() << std::endl
+    //<< "Image size: " << images[0].size() << std::endl;
+
+  //for (int i = 0; i < 3; i++) {
+    //for (int j = 0; j < images[i].size(); j++) {
+      //std::cout << images[i][j] << ",";
+    //}
+    //std::cout << " label=" << (int)labels[i] << std::endl;
+  //}
+  //return 0;
+//}

src/test.cu

@@ -1,9 +1,13 @@
 
 #include "marian.h"
+#include "mnist.h"
 
 using namespace std;
 
 int main(int argc, char** argv) {
+  /*auto images = datasets::mnist::ReadImages("../examples/mnist/t10k-images-idx3-ubyte");*/
+  /*auto labels = datasets::mnist::ReadLabels("../examples/mnist/t10k-labels-idx1-ubyte");*/
+  /*std::cerr << images.size() << " " << images[0].size() << std::endl;*/
 
   using namespace marian;
   using namespace keywords;