c++:比较求1亿个素数性能 (使用或不使用stl容器性能对比)

#include <iostream>
#include <bitset>
#include <ctime>
#include <time.h>
#include <string.h>
#include <cstring>
#include <cstdio>

using namespace std;

int sieve_stl();
int sieve();

int main()
{
    clock_t start = clock();
    cout << sieve();
    cout << " " << (clock() - start) << " sec\n";

    start = clock();
    cout << sieve_stl();
    cout << " " << (clock() - start) << " sec\n";
}

int sieve_stl()
{
    bitset <100000000>& p = *new bitset<100000000>;
    p.set();

    int num = 100000000 - 2; // i = 0, 1除外
    for (int i = 2; i <= 10000; i++) {
        if (p.test(i))
            for (int j = i * i; j < p.size(); j += i)
                if (p.test(j) && num--)
                    p.reset(j);
    }

    delete[] &p;

    return num;
}

int sieve()
{
    unsigned int *p = (unsigned int *)malloc(12500000);

    memset(p, -1, 12500000);

    int num = 100000000 - 2; // i = 0, 1除外
    for (int i = 2; i <= 10000; i++)
        if (p[i/32] & (1 << i % 32))
            for (int j = i * i; j < 100000000; j += i)
                if (p[j/32] & (1 << j % 32) && num--)
                    p[j/32] &= ~(1 << j % 32);

    free(p);

    return num;
}

/*
 * 使用STL容器的过程败北了,而且败得很惨.1亿次调用中,主要都是些对象调用操作太费时间.
 */