either this benchmark is fucked or C++ style I/O is slow as shit

benchmark.cpp

#include <iostream>
#include <chrono>
#include <vector>
#include <fstream>
#include <string>
#include <cstdlib>
#include <cstdio>

using namespace std;
using namespace std::chrono;

// Function to generate test data file with one integer per line
void generate_test_data(const string& filename, int n) {
    ofstream file(filename);
    for (int i = 0; i < n; i++) {
        file << i << "\n";  // One integer per line
    }
    file.close();
}

// Benchmark functions that directly read from stdin
// Each version is compiled separately to ensure clean test environment

// Standard C++ I/O
int benchmark_standard() {
    auto start = high_resolution_clock::now();
    
    vector<int> numbers;
    int x;
    while (cin >> x) {
        numbers.push_back(x);
    }
    
    auto end = high_resolution_clock::now();
    auto duration = duration_cast<microseconds>(end - start);
    
    cout << "Standard I/O: Read " << numbers.size() << " numbers in " 
         << duration.count() << " microseconds" << endl;
    
    return 0;
}

// Optimized C++ I/O
int benchmark_optimized() {
    // Optimized settings
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    auto start = high_resolution_clock::now();
    
    vector<int> numbers;
    int x;
    while (cin >> x) {
        numbers.push_back(x);
    }
    
    auto end = high_resolution_clock::now();
    auto duration = duration_cast<microseconds>(end - start);
    
    cout << "Optimized I/O: Read " << numbers.size() << " numbers in " 
         << duration.count() << " microseconds" << endl;
    
    return 0;
}

// C-style I/O
int benchmark_c_style() {
    auto start = high_resolution_clock::now();
    
    vector<int> numbers;
    int x;
    while (scanf("%d", &x) == 1) {
        numbers.push_back(x);
    }
    
    auto end = high_resolution_clock::now();
    auto duration = duration_cast<microseconds>(end - start);
    
    printf("C-style I/O: Read %zu numbers in %lld microseconds\n", 
           numbers.size(), (long long)duration.count());
    
    return 0;
}

// Main function to generate data and compile separate benchmarks
int main(int argc, char* argv[]) {
    if (argc < 2) {
        cerr << "Usage: " << argv[0] << " [generate|standard|optimized|c_style]" << endl;
        return 1;
    }
    
    string mode = argv[1];
    
    if (mode == "generate") {
        const int n = 1000000; // 1 million numbers
        const string filename = "test_data.txt";
        cout << "Generating test data with " << n << " integers (one per line)..." << endl;
        generate_test_data(filename, n);
    }
    else if (mode == "standard") {
        return benchmark_standard();
    }
    else if (mode == "optimized") {
        return benchmark_optimized();
    }
    else if (mode == "c_style") {
        return benchmark_c_style();
    }
    else {
        cerr << "Unknown mode: " << mode << endl;
        return 1;
    }
    
    return 0;
}

results

wkh@mayhem ~/c/sync_with_stdio_benchmark> wc -l test_data.txt; head test_data.txt; tail test_data.txt
 1000000 test_data.txt
0
1
2
3
4
5
6
7
8
9
999990
999991
999992
999993
999994
999995
999996
999997
999998
999999
wkh@mayhem ~/c/sync_with_stdio_benchmark> ./run_benchmarks.sh
Compiling benchmark application...

Running standard I/O benchmark...
Standard I/O: Read 1000000 numbers in 1015893 microseconds

real    0m1.019s
user    0m1.005s
sys     0m0.012s

Running optimized I/O benchmark...
Optimized I/O: Read 1000000 numbers in 992252 microseconds

real    0m0.996s
user    0m0.984s
sys     0m0.011s

Running C-style I/O benchmark...
C-style I/O: Read 1000000 numbers in 49667 microseconds

real    0m0.053s
user    0m0.048s
sys     0m0.004s

run_benchmarks.sh

#!/bin/bash

BENCHMARK_APP="./benchmark_app"

# Compile the benchmark application
echo "Compiling benchmark application..."
g++ -std=c++17 -O3 -march=native benchmark.cpp -o $BENCHMARK_APP

echo -e "\nRunning standard I/O benchmark..."
time $BENCHMARK_APP standard < test_data.txt

echo -e "\nRunning optimized I/O benchmark..."
time $BENCHMARK_APP optimized < test_data.txt

echo -e "\nRunning C-style I/O benchmark..."
time $BENCHMARK_APP c_style < test_data.txt