set-count.cpp

#include <unordered_set>
#include <chrono>
using stopwatch = std::chrono::high_resolution_clock;

static const size_t count = 4 * 1024 * 1024;

void setup( std::unordered_set<size_t>& set )
{
	srand( 0 );
	for( size_t i = 0; i < count; i++ )
	{
		if( rand() > ( RAND_MAX / 2 ) )
			set.insert( i );
	}
	// printf( "setup ok, %i values\n", (int)set.size() );
}

static bool __declspec( noinline ) exists_count( const std::unordered_set<size_t>& set, size_t k )
{
	return 0 != set.count( k );
}
static bool __declspec( noinline ) exists_find( const std::unordered_set<size_t>& set, size_t k )
{
	return set.find( k ) != set.end();
}
int test( const std::unordered_set<size_t>& set, bool( *ex )( const std::unordered_set<size_t>& set, size_t k ) )
{
	int res = 0;
	for( size_t i = 0; i < count; i++ )
		if( ex( set, i ) );
	res++;
	return res;
}

int main()
{
	std::unordered_set<size_t> us;
	setup( us );
	const auto start = stopwatch::now();
	// const int res = test( us, &exists_count );
	const int res = test( us, &exists_find );
	printf( "%i\n", res );
	const auto stop = stopwatch::now();
	const auto duration = stop - start;
	typedef std::chrono::duration<double, std::milli> ms;
	const ms d = duration;
	printf( "%f ms\n", d.count() );
	return 0;
}