Sort function is slower than std::sort

When you copied the code did you just stick the code from std::sort into sort2 verbatim? i.e. sort2 isn't part of the std namespace. As it's not part of the std namespace it won't be using all the lovely specialisations for swap that are kicking around which may be the cause of the lack of speed.

Do a search for Koenig lookup (or argument dependent lookup - ADL) which explains how the compiler searches namespaces for names. I may be completely wrong but this sort of thing has bitten me in the past when I've moved stuff between namespaces.

Cheers,

Ash

template<class _RanIt,
	class _Diff,
	class _Pr> inline
	void _Sort(_RanIt _First, _RanIt _Last, _Diff _Ideal, _Pr _Pred)
	{	// order [_First, _Last), using _Pred
	_Diff _Count;
	for (;<big> _ISORT_MAX < (_Count = _Last - _First) </big>&& 0 < _Ideal; )
		{	// divide and conquer by quicksort
		pair<_RanIt, _RanIt> _Mid =
			_Unguarded_partition(_First, _Last, _Pred);
		_Ideal /= 2, _Ideal += _Ideal / 2;	// allow 1.5 log2(N) divisions
		if (_Mid.first - _First < _Last - _Mid.second)	// loop on larger half
			_Sort(_First, _Mid.first, _Ideal, _Pred), _First = _Mid.second;
		else
			_Sort(_Mid.second, _Last, _Ideal, _Pred), _Last = _Mid.first;
		}
	if (<big>_ISORT_MAX < _Count</big>)
		{	// heap sort if too many divisions
		std::make_heap(_First, _Last, _Pred);
		std::sort_heap(_First, _Last, _Pred);
		}
	else if (1 < _Count)
		_Insertion_sort(_First, _Last, _Pred);	// small, insertion sort
	}

This is the code of _Sort , heap sort is closed by _ISORT_MAX.
In release heap sort may be opened .

Changed the source ,my sort function is close to the speed of std::sort in 1M size vector.

const int _ISORT_MAX2 = 64*64;
for (;_ISORT_MAX2 < (_Count = _Last - _First) && 0 < _Ideal; )

Adjust the value of _ISORT_MAX2 , sort function will get different speed ,even quicker than std::sort.