Even after clear, seems to be memory is not cleaned up when I use boost::fast_pool_allocator. Can someone help in correct usage?

typedef std::set<unsigned int, std::less< unsigned int>, boost::fast_pool_allocator< unsigned int> > IDSET;

int main()

{

          IDSET set;

          WriteMemoryUsage();

for (int i=0;i<1000000;i++)

                   set.insert(i);

          WriteMemoryUsage();

          set.clear();

          WriteMemoryUsage();

return 1;

}

In WriteMemoryUsage

Processid: 4836

Peak Memory used: 1155072

Working Set Size: 2744320

Page File Usage: 1155072

Processid: 4836

Peak Memory used: 34816000

Working Set Size: 36528128

Page File Usage: 34816000

Processid: 4836

Peak Memory used: 34816000

Working Set Size: 36532224

Page File Usage: 34816000

Regards,

UJ