Add C++ array arithmetic program

Author: rafmudaf

.gitignore

@@ -1,2 +1,3 @@
 .pytest_cache/
 **.pyc
+build/

CMakeLists.txt

@@ -0,0 +1,7 @@
+cmake_minimum_required(VERSION 3.10)
+
+# set the project name
+project(arraymath)
+
+# add the executable
+add_executable(arraymath array_arithmetic.cpp)

array_arithmetic.cpp

@@ -0,0 +1,86 @@
+
+#include <iostream>
+#include <vector>
+#include <time.h>
+
+
+int main()
+{
+
+    std::cout << "Configuration" << std::endl;
+
+    // Python float is 64 bit / 8 byte
+    int ARRAY_SIZE = 1000 * 1000 * 5;
+    // int ARRAY_SIZE =  5;
+    std::cout << "- Size of data array: " << ARRAY_SIZE * 8 / (1000 * 1000) << "MB" << std::endl;
+
+    int N = 10;
+    std::cout << "- Number of iterations to average: " << N << std::endl;
+
+
+    time_t t_start, t_end;
+    double elapsed_time = 0.0;
+    double average;
+
+    {
+        std::vector<double> array1(ARRAY_SIZE), array2(ARRAY_SIZE), buffer_array(ARRAY_SIZE);
+        std::vector<int> index_map(ARRAY_SIZE);
+
+        for(int i=0; i<ARRAY_SIZE; i++) {
+            index_map[i] = rand()%ARRAY_SIZE;
+        }
+
+        for (int i=0; i<N; i++) {
+            t_start = time(NULL);
+            for (int j=0; j<ARRAY_SIZE; j++) {
+                int index = index_map[j];
+                buffer_array[j] = array1[index] * array2[index] + array1[index] * array2[index];
+            }
+            t_end = time(NULL);
+
+            elapsed_time += difftime(t_end, t_start);
+        }
+        average = elapsed_time / N;
+        std::cout << "Non-contiguous access, vectorization: " << elapsed_time << " " << average << std::endl;
+    }
+
+
+    {
+        std::vector<double> array1(ARRAY_SIZE), array2(ARRAY_SIZE), buffer_array(ARRAY_SIZE);
+        std::vector<int> index_map(ARRAY_SIZE);
+
+        for(int i=0; i<ARRAY_SIZE; i++) {
+            index_map[i] = i;
+        }
+
+        for (int i=0; i<N; i++) {
+            t_start = time(NULL);
+            for (int j=0; j<ARRAY_SIZE; j++) {
+                int index = index_map[j];
+                buffer_array[j] = array1[index] * array2[index] + array1[index] * array2[index];
+            }
+            t_end = time(NULL);
+
+            elapsed_time += difftime(t_end, t_start);
+        }
+        average = elapsed_time / N;
+        std::cout << "Contiguous access, vectorization: " << elapsed_time << " " << average << std::endl;
+    }
+
+
+    // {
+    //     std::vector<double> array1(ARRAY_SIZE), array2(ARRAY_SIZE), buffer_array(ARRAY_SIZE);
+
+    //     for (int i=0; i<N; i++) {
+    //         t_start = time(NULL);
+    //         buffer_array = array1 * array2 + array1 * array2;
+    //         t_end = time(NULL);
+
+    //         elapsed_time += difftime(t_end, t_start);
+    //     }
+    //     average = elapsed_time / N;
+    //     std::cout << "No indexing: " << elapsed_time << " " << average << std::endl;
+    // }
+
+    return 0;
+}