strcpy.c

// Copyright © 2017 Martin Ueding <dev@martin-ueding.de>
// Licensed under the MIT license

// Compiled with:
//
//     gcc -Wall -Wpedantic -fopenmp strcpy.c -o strcpy -O3 -g

/*
String length: 1,000,000,000
short_strcpy:   0.961368
short_strcpy:   0.709614
longer_strcpy:  0.695906
longer_strcpy:  0.698939
other_strcpy:   0.698368
other_strcpy:   0.693769
another_strcpy: 0.708977
another_strcpy: 0.711919
strcpy:         0.198001
strcpy:         0.205245
memcpy:         6.49998e-08
memcpy:         6.00012e-08

String length: 100,000,000
short_strcpy:   0.119037
short_strcpy:   0.0705183
longer_strcpy:  0.0690453
longer_strcpy:  0.0691149
other_strcpy:   0.070922
other_strcpy:   0.0715886
another_strcpy: 0.0706077
another_strcpy: 0.0704344
strcpy:         0.0207186
strcpy:         0.0242169
memcpy:         5.10008e-08
memcpy:         6.0998e-08

String length: 10,000,000
short_strcpy:   0.0218649
short_strcpy:   0.0138642
longer_strcpy:  0.0113662
longer_strcpy:  0.0105511
other_strcpy:   0.0101318
other_strcpy:   0.00947807
another_strcpy: 0.00931944
another_strcpy: 0.00907402
strcpy:         0.00201328
strcpy:         0.00325
memcpy:         6.60002e-08
memcpy:         5.4999e-08

String length: 1,000,000
short_strcpy:   0.00257647
short_strcpy:   0.00201034
longer_strcpy:  0.00175444
longer_strcpy:  0.00172597
other_strcpy:   0.00174712
other_strcpy:   0.00175475
another_strcpy: 0.00177107
another_strcpy: 0.0017567
strcpy:         0.000258751
strcpy:         0.000230961
memcpy:         1.06e-07
memcpy:         9.19972e-08

String length: 100,000
short_strcpy:   0.000362797
short_strcpy:   0.000261451
longer_strcpy:  0.000261319
longer_strcpy:  0.000293498
other_strcpy:   0.00026597
other_strcpy:   0.000260578
another_strcpy: 0.000280667
another_strcpy: 0.000274899
strcpy:         2.7554e-05
strcpy:         1.5588e-05
memcpy:         1.12999e-07
memcpy:         1.20002e-07
*/

#include <omp.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define LEN 10000000UL

void short_strcpy(char *d, char *s) {
    while ((*d++ = *s++));
}

void longer_strcpy(char *d, char *s) {
    size_t i = 0;
    while (s[i] != '\0') {
        d[i] = s[i];
        i++;
    }
    d[i] = s[i];
}

void other_strcpy(char *d, char *s) {
    size_t i = 0;
    while ((d[i] = s[i]) != '\0') {
        i++;
    }
}

void another_strcpy(char *d, char *s) {
    while ((*d++ = *s++) != '\0');
}

int main(int argc, char **argv) {
    char *s = malloc(LEN);
    char *d = malloc(LEN);

    double start, end;

    printf("String length: %ld\n", LEN);

    memset(s, 1, LEN);
    s[LEN - 1] = 0;

    // Warm the caches.
    start = omp_get_wtime();
    short_strcpy(d, s);
    end = omp_get_wtime();
    printf("short_strcpy:   %g\n", end - start);

    start = omp_get_wtime();
    short_strcpy(d, s);
    end = omp_get_wtime();
    printf("short_strcpy:   %g\n", end - start);

    start = omp_get_wtime();
    longer_strcpy(d, s);
    end = omp_get_wtime();
    printf("longer_strcpy:  %g\n", end - start);

    start = omp_get_wtime();
    longer_strcpy(d, s);
    end = omp_get_wtime();
    printf("longer_strcpy:  %g\n", end - start);

    start = omp_get_wtime();
    other_strcpy(d, s);
    end = omp_get_wtime();
    printf("other_strcpy:   %g\n", end - start);

    start = omp_get_wtime();
    other_strcpy(d, s);
    end = omp_get_wtime();
    printf("other_strcpy:   %g\n", end - start);

    start = omp_get_wtime();
    another_strcpy(d, s);
    end = omp_get_wtime();
    printf("another_strcpy: %g\n", end - start);

    start = omp_get_wtime();
    another_strcpy(d, s);
    end = omp_get_wtime();
    printf("another_strcpy: %g\n", end - start);

    start = omp_get_wtime();
    strcpy(d, s);
    end = omp_get_wtime();
    printf("strcpy:         %g\n", end - start);

    start = omp_get_wtime();
    strcpy(d, s);
    end = omp_get_wtime();
    printf("strcpy:         %g\n", end - start);

    start = omp_get_wtime();
    memcpy(d, s, LEN);
    end = omp_get_wtime();
    printf("memcpy:         %g\n", end - start);

    start = omp_get_wtime();
    memcpy(d, s, LEN);
    end = omp_get_wtime();
    printf("memcpy:         %g\n", end - start);

    return 0;
}