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Precompute indices to avoid clever optimizations

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This commit is contained in:
Peter Dimov 2021-11-29 04:54:47 +02:00
parent ad51b34438
commit bbd0eedb5f
1 changed files with 42 additions and 16 deletions
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58
benchmark/uint64.cpp
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@ -33,29 +33,55 @@ static void print_time( std::chrono::steady_clock::time_point & t1, char const*
constexpr unsigned N = 2'000'000;
constexpr int K = 10;
template<class Map> void test_insert( Map& map, std::chrono::steady_clock::time_point & t1 )
static std::vector< std::uint64_t > indices1, indices2, indices3;
static void init_indices()
{
for( unsigned i = 1; i <= N; ++i )
indices1.push_back( 0 );
for( unsigned i = 1; i <= N*2; ++i )
{
map.insert( { i, i } );
indices1.push_back( i );
}
print_time( t1, "Consecutive insert", 0, map.size() );
indices2.push_back( 0 );
{
boost::detail::splitmix64 rng;
for( unsigned i = 1; i <= N; ++i )
for( unsigned i = 1; i <= N*2; ++i )
{
map.insert( { rng(), i } );
indices2.push_back( rng() );
}
}
indices3.push_back( 0 );
for( unsigned i = 1; i <= N*2; ++i )
{
indices3.push_back( (std::uint64_t)i << 32 );
}
}
template<class Map> void test_insert( Map& map, std::chrono::steady_clock::time_point & t1 )
{
for( unsigned i = 1; i <= N; ++i )
{
map.insert( { indices1[ i ], i } );
}
print_time( t1, "Consecutive insert", 0, map.size() );
for( unsigned i = 1; i <= N; ++i )
{
map.insert( { indices2[ i ], i } );
}
print_time( t1, "Random insert", 0, map.size() );
for( unsigned i = 1; i <= N; ++i )
{
map.insert( { (std::uint64_t)i << 32, i } );
map.insert( { indices3[ i ], i } );
}
print_time( t1, "Consecutive shifted insert", 0, map.size() );
@ -73,7 +99,7 @@ template<class Map> void test_lookup( Map& map, std::chrono::steady_clock::time_
{
for( unsigned i = 1; i <= N * 2; ++i )
{
auto it = map.find( i );
auto it = map.find( indices1[ i ] );
if( it != map.end() ) s += it->second;
}
}
@ -84,11 +110,9 @@ template<class Map> void test_lookup( Map& map, std::chrono::steady_clock::time_
for( int j = 0; j < K; ++j )
{
boost::detail::splitmix64 rng;
for( unsigned i = 1; i <= N * 2; ++i )
{
auto it = map.find( rng() );
auto it = map.find( indices2[ i ] );
if( it != map.end() ) s += it->second;
}
}
@ -101,7 +125,7 @@ template<class Map> void test_lookup( Map& map, std::chrono::steady_clock::time_
{
for( unsigned i = 1; i <= N * 2; ++i )
{
auto it = map.find( (std::uint64_t)i << 32 );
auto it = map.find( indices3[ i ] );
if( it != map.end() ) s += it->second;
}
}
@ -136,7 +160,7 @@ template<class Map> void test_erase( Map& map, std::chrono::steady_clock::time_p
{
for( unsigned i = 1; i <= N; ++i )
{
map.erase( i );
map.erase( indices1[ i ] );
}
print_time( t1, "Consecutive erase", 0, map.size() );
@ -146,7 +170,7 @@ template<class Map> void test_erase( Map& map, std::chrono::steady_clock::time_p
for( unsigned i = 1; i <= N; ++i )
{
map.erase( rng() );
map.erase( indices2[ i ] );
}
}
@ -154,7 +178,7 @@ template<class Map> void test_erase( Map& map, std::chrono::steady_clock::time_p
for( unsigned i = 1; i <= N; ++i )
{
map.erase( (std::uint64_t)i << 32 );
map.erase( indices3[ i ] );
}
print_time( t1, "Consecutive shifted erase", 0, map.size() );
@ -162,7 +186,7 @@ template<class Map> void test_erase( Map& map, std::chrono::steady_clock::time_p
std::cout << std::endl;
}
std::vector< std::pair<std::string, long long> > times;
static std::vector< std::pair<std::string, long long> > times;
template<template<class...> class Map> void test( char const* label )
{
@ -204,6 +228,8 @@ template<class K, class V> using multi_index_map = multi_index_container<
int main()
{
init_indices();
test<std::unordered_map>( "std::unordered_map" );
test<boost::unordered_map>( "boost::unordered_map" );
test<multi_index_map>( "multi_index_map" );