Recently I was solving one of the Project Euler problems #94 in C++ and thought of implementing the same in Rust and comparing their execution times
SPOILER ALERT: contains a solution for the project Euler problem #94
Turns out the same implementation in Rust is twice as slow as compared to C++ solution
I would like to know the cause of this. Thank you!
#include <chrono>
#include <cmath>
#include <iostream>
#include <thread>
#include <vector>
const uint64_t MAX = 1'000'000'000; // Set the value of MAX here
const uint64_t THREAD_COUNT = 10;
void calculatePerimeter(uint64_t thread_id, uint64_t& perimeter) {
uint64_t start_a = 1 + thread_id;
for (uint64_t a = start_a; 3 * a + 1 <= MAX; a += THREAD_COUNT) {
std::array<uint64_t, 2> c_values = { a - 1, a + 1 };
for (uint64_t c : c_values) {
if (c > 0) {
if (2 * a + c > MAX) {
continue;
}
uint64_t second = 4 * a * a - c * c;
uint64_t root = static_cast<uint64_t>(std::sqrt(second));
if (root * root != second) {
continue;
}
second = root;
uint64_t numerator = c * second;
if (numerator > 0 && numerator % 4 == 0) {
perimeter += 2 * a + c;
}
}
}
}
}
int main() {
std::vector<std::thread> threads;
std::vector<uint64_t> perimeters(THREAD_COUNT);
auto start_time = std::chrono::high_resolution_clock::now();
for (uint64_t thread_id = 0; thread_id < THREAD_COUNT; ++thread_id) {
threads.emplace_back(calculatePerimeter, thread_id, std::ref(perimeters[thread_id]));
}
uint64_t total_perimeter = 0;
for (auto& thread : threads) {
thread.join();
}
for (const auto& perimeter : perimeters) {
total_perimeter += perimeter;
}
auto end_time = std::chrono::high_resolution_clock::now();
auto elapsed_time =
std::chrono::duration_cast<std::chrono::milliseconds>(end_time - start_time);
std::cout << "Answer = " << total_perimeter << std::endl;
std::cout << "Elapsed time: " << elapsed_time.count() << " milliseconds" << std::endl;
return 0;
}
use std::thread;
use std::time::Instant;
fn main() {
const MAX: u64 = 1_000_000_000; // Set the value of MAX here
const THREAD_COUNT: u64 = 10;
let mut handles = Vec::with_capacity(THREAD_COUNT as usize);
let start_time = Instant::now(); // Start measuring the execution time
for thread_id in 0..THREAD_COUNT {
let handle = thread::spawn(move || {
let start_a = 1 + thread_id;
let mut perimeter = 0;
for a in (start_a..).step_by(THREAD_COUNT as usize) {
let c_values = [a - 1, a + 1];
for &c in &c_values {
if c > 0 {
if 2 * a + c > MAX {
continue;
}
let mut second = 4 * a * a - c * c;
let root = (second as f64).sqrt() as u64;
if root * root != second {
continue;
}
second = root;
let numerator = c * second;
if numerator > 0 && numerator % 4 == 0 {
perimeter += 2 * a + c;
}
}
}
if 3 * a + 1 > MAX {
break;
}
}
perimeter
});
handles.push(handle);
}
let mut total_perimeter = 0;
for handle in handles {
total_perimeter += handle.join().unwrap();
}
let elapsed_time = start_time.elapsed(); // Calculate the elapsed time
println!("Answer = {}", total_perimeter);
println!("Elapsed time: {:?}", elapsed_time);
}
UPD: I was using rustc to create the binary
