Measure performance of qsort(3) vs std::sort()

README.rst

C qsort(3) vs C++ std::sort()

On my hardware C++ sort implementation is almost three times faster than Mac OS X libc's:

λ ~/tmp/5448488/ master* make clean && make test
rm -f sort_cpp sort_c
${CXX:-c++} -std=c++11 -O3 sort.cpp -o sort_cpp
${CC:-cc} -O3 sort.c -o sort_c
./sort_cpp
Time: 11 seconds.
./sort_c
Time: 28 seconds.

Makefile

CXX			= $${CXX:-c++}
CXXFLAGS	= -std=c++11 -O3
CC			= $${CC:-cc}
CFLAGS		= -O3

all: sort_cpp sort_c test

sort_cpp: sort.cpp
	$(CXX) $(CXXFLAGS) $^ -o $@

sort_c: sort.c
	$(CC) $(CFLAGS) $^ -o $@

test: sort_cpp sort_c
	./sort_cpp
	./sort_c

clean:
	rm -f sort_cpp sort_c

sort.c

#include <sys/time.h>

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


#define ARRAY_SZ	100000000

static int
int_cmp(const void *i1, const void *i2)
{

	return *(int *)i1 - *(int *)i2;
}

int
main(void)
{
	int i, *ints;
	struct timeval t1, t2;

	ints = malloc(ARRAY_SZ * sizeof(int));
	if (ints == NULL)
		exit(EX_TEMPFAIL);

	for (i = 0; i < ARRAY_SZ; i++)
		ints[i] = (int)random();

	gettimeofday(&t1, NULL);
	qsort(ints, ARRAY_SZ, sizeof(int), int_cmp);
	gettimeofday(&t2, NULL);

	printf("Time: %ld seconds.\n", t2.tv_sec - t1.tv_sec);

	return EX_OK;
}

sort.cpp

#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <vector>


int main() {
	std::vector<int> ints;
	std::time_t time;

	for (int i = 0; i < 100000000; ++i)
		ints.push_back(std::rand());

	time = std::time(NULL);
	std::sort(ints.begin(), ints.end(), std::greater<int>());
	std::cout << "Time: " << std::time(NULL) - time
		<< " seconds." << std::endl;
}