Re: app crash when there's more than 3000 entries in std::map ?

From:

mast4as <mast4as@yahoo.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 12 Aug 2010 10:34:57 -0700 (PDT)

Message-ID:

<908b7f67-a5f1-494a-b104-bfdca92b85c7@v15g2000yqe.googlegroups.com>

Sorry you need to add

#include <ext/hash_map>
using namespace __gnu_cxx;
namespace __gnu_cxx {

// hash specialisation to allow hashing of strings
template<>
struct hash<std::string>
{
size_t operator()(const std::string &__s) const { return
__stl_hash_string(__s.c_str()); }
};

} // namespace __gnu_cxx OR std

at the top if you want this to compile. But hash_map and map behaves
the same

using c++ (GCC) 4.1.2 20080704 (Red Hat 4.1.2-44)
On Aug 12, 6:33 pm, mast4as <mast...@yahoo.com> wrote:

Hi everyone

I have this strange behaviour happening with this code which I can't
explain. On my computer when I set nt with a value greater than 3000
it crashes. Is there a max number of keys I can use with a std::map ?

thanks a lot

#include <vector>
#include <iostream>
#include <map>

#include <string>

int main()
{
        float t = clock();
        int nt = 3000;
#if 1
        hash_map<std::string, int, hash<std::string> > mymap;
        for ( int i = 0; i < nt; ++i )
        {
                string tmp = "test" + i;
                mymap[ tmp ] = i;
        }
        for ( int i = 0; i < 10e5; ++i )
        {
                int a = (int)(drand48() * nt);
                string tmp = "test" + a;
                hash_map<std::string, int, hash<std::stri=

ng> >::iterator it =

mymap.find( tmp );
                if ( it != mymap.end() )
                {
                }
                else
                {
                        printf("not found\n");
                }
        }
        unsigned max_size = mymap.max_size();
        printf("%d\n", max_size );

#else
        std::map<std::string, int> mymap;
        for ( int i = 0; i < nt; ++i )
        {
                string tmp = "test" + i;
                mymap[ tmp ] = i;
        }
        for ( int i = 0; i < 10e5; ++i )
        {
                int a = (int)(drand48() * nt);
                string tmp = "test" + a;
                std::map<std::string, int>::iterator it =

= mymap.find( tmp );

                if ( it != mymap.end() )
                {
                }
                else
                {
                        printf("not found\n");
                }
        }

        unsigned max_size = mymap.max_size();
        printf("%d\n", max_size );

#endif
        printf("time %f\n", (clock() - t ) / float( CLOCKS_PER_SE=

C ) );

return 0;

}

#endif