118
edits
Changes
→Example Of A False Sharing
= '''Example Of A False Sharing''' =
#include <thread>
#include <vector>
#include <iostream>
#include <chrono>
using namespace std;
const int sizeOfNumbers = 10000; // Size of vector numbers
const int sizeOfSum = 2; // Size of vector sum
void sumUp(const vector<int> numbers, vector<long>& sum, int id) {
for (int i = 0; i < numbers.size(); i++) {
if (i % sizeOfSum == id) {
sum[id] += I;
}
}
// The output of this sum
cout << "sum " << id << " = " << sum[id] << endl;
}
int main() {
vector<int> numbers;
for (int i = 0; i < sizeOfNumbers; i++) { //Initialize vector numbers to 0 to 100
numbers.push_back(i);
}
cout << "-----Thread-----" << endl;
{ // Thread
vector<long> sum(sizeOfSum, 0); //Set size=sizeOfSum and all to 0
auto start = chrono::steady_clock::now();
vector<thread> td;
for (int i = 0; i < sizeOfSum; i++) {
td.emplace_back(sumUp, numbers, ref(sum), I);
}
for (int i = 0; i < sizeOfSum; i++) {
td[i].join();
}
auto end = chrono::steady_clock::now();
cout << "Thread time consumption: " << chrono::duration_cast<chrono::microseconds>(end - start).count() << "ms" << endl;
}
cout << endl << "-----Serial-----" << endl;
{ // Serial
vector<long> sum(sizeOfSum, 0);
auto start = chrono::steady_clock::now();
for (int i = 0; i < sizeOfSum; i++) {
sumUp(numbers, sum, I);
}
auto end = chrono::steady_clock::now();
cout << "Serial time consumption: " << chrono::duration_cast<chrono::microseconds>(end - start).count() << "ms" << endl;
}
}
In this program code, we can see that at the beginning of the main function we declare a vector numbers and initialize it from 0 to 100. We can also see in the main function that the code is divided into two main blocks. The first block is the Thread block, which is executed concurrently using multiple threads. While the second block is the Serial block, it is executed concurrently using normal serial logic.
