From 86a58060bca41a0273e74f2fab7f9cafc2bbdaae Mon Sep 17 00:00:00 2001
From: romang <romang@amu.edu.pl>
Date: Tue, 13 Sep 2016 18:56:19 +0200
Subject: [PATCH] MNIST loader returns 1d vector

---
 src/mnist.h | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/src/mnist.h b/src/mnist.h
index 7727bacc..8e94931f 100644
--- a/src/mnist.h
+++ b/src/mnist.h
@@ -1,4 +1,4 @@
-#pragma once
+//#pragma once
 
 #include <string>
 #include <iostream>
@@ -16,7 +16,7 @@ auto reverseInt = [](int i) {
   return ((int)c1 << 24) + ((int)c2 << 16) + ((int)c3 << 8) + c4;
 };
 
-std::vector<std::vector<float>> ReadImages(const std::string& full_path) {
+std::vector<float> ReadImages(const std::string& full_path, int& number_of_images, int& image_size) {
   std::ifstream file(full_path);
 
   if (! file.is_open())
@@ -30,20 +30,18 @@ std::vector<std::vector<float>> ReadImages(const std::string& full_path) {
   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));
+  image_size = n_rows * n_cols;
+  int n = number_of_images * image_size;
+  std::vector<float> _dataset(n);
   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;
-    }
+  for (int i = 0; i < n; i++) {
+    file.read((char*)&pixel, sizeof(pixel));
+    _dataset[i] = pixel / 255.0f;
   }
   return _dataset;
 }
@@ -77,16 +75,17 @@ std::vector<int> ReadLabels(const std::string& full_path) {
 
 
 //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");
+  //int numImg, imgSize;
+  //auto images = datasets::mnist::ReadImages("../examples/mnist/t10k-images-idx3-ubyte", numImg, imgSize);
+  //auto labels = datasets::mnist::ReadLabels("../examples/mnist/t10k-labels-idx1-ubyte");
 
   //std::cout
-    //<< "Number of images: " << images.size() << std::endl
-    //<< "Image size: " << images[0].size() << std::endl;
+    //<< "Number of images: " << numImg << std::endl
+    //<< "Image size: " << imgSize << std::endl;
 
   //for (int i = 0; i < 3; i++) {
-    //for (int j = 0; j < images[i].size(); j++) {
-      //std::cout << images[i][j] << ",";
+    //for (int j = 0; j < imgSize; j++) {
+      //std::cout << images[(i * imgSize) + j] << ",";
     //}
     //std::cout << " label=" << (int)labels[i] << std::endl;
   //}