performance of string conversions

strconv.cpp

#include <cstring>
#include <cmath>
#include <cstdio>
#include <ctime>
#include <cstdlib>
#include <sstream>

#define NITER 5000000

int main() {
    const char* pi_s = "    3.14159265358979323846   "; // M_PI

    float f;
    clock_t t;

    f = atoi(pi_s);
    printf("test %f\n", f);

    t = clock();
    for(size_t i = 0; i < NITER; i++)
        f = atof(pi_s);
    printf("strtof %fs\n", float(clock() - t)/CLOCKS_PER_SEC);

    t = clock();
    for(size_t i = 0; i < NITER; i++)
        f = strtof(pi_s, NULL);
    printf("atof %fs \n", float(clock() - t)/CLOCKS_PER_SEC);

    t = clock();
    for(size_t i = 0; i < NITER; i++)
        sscanf(pi_s, "%f", &f);
    printf("sscanf %fs\n", float(clock() - t)/CLOCKS_PER_SEC);

    t = clock();
    std::stringstream ss;
    for(size_t i = 0; i < NITER; i++) {
        ss.str(pi_s);
        ss.clear();
        ss >> f;
    }
    printf("std::stringstream reuse %fs\n", float(clock() - t)/CLOCKS_PER_SEC);

    t = clock();
    for(size_t i = 0; i < NITER; i++)
        std::stringstream(pi_s) >> f;
    printf("std::stringstream %fs\n", float(clock() - t)/CLOCKS_PER_SEC);

    return 0;
}