diff options
Diffstat (limited to 'libstdc++-v3/testsuite/performance/23_containers/insert_erase/41975.cc')
| -rw-r--r-- | libstdc++-v3/testsuite/performance/23_containers/insert_erase/41975.cc | 175 |
1 files changed, 143 insertions, 32 deletions
diff --git a/libstdc++-v3/testsuite/performance/23_containers/insert_erase/41975.cc b/libstdc++-v3/testsuite/performance/23_containers/insert_erase/41975.cc index 30fc105c272..a5dae41dc60 100644 --- a/libstdc++-v3/testsuite/performance/23_containers/insert_erase/41975.cc +++ b/libstdc++-v3/testsuite/performance/23_containers/insert_erase/41975.cc @@ -17,56 +17,167 @@ // with this library; see the file COPYING3. If not see // <http://www.gnu.org/licenses/>. -#include <cassert> +#include <sstream> #include <unordered_set> #include <testsuite_performance.h> -int main() +namespace { - using namespace __gnu_test; + // Bench using an unordered_set<int>. Hash functor for int is quite + // predictable so it helps bench very specific use cases. + template<bool use_cache> + void bench() + { + using namespace __gnu_test; + std::ostringstream ostr; + ostr << "unordered_set<int> " << (use_cache ? "with" : "without") + << " cache"; + const std::string desc = ostr.str(); + + time_counter time; + resource_counter resource; + + const int nb = 200000; + start_counters(time, resource); + + std::__unordered_set<int, std::hash<int>, std::equal_to<int>, + std::allocator<int>, use_cache> us; + for (int i = 0; i != nb; ++i) + us.insert(i); + + stop_counters(time, resource); + ostr.str(""); + ostr << desc << ": first insert"; + report_performance(__FILE__, ostr.str().c_str(), time, resource); + + start_counters(time, resource); + + // Here is the worst erase use case when hashtable implementation was + // something like vector<forward_list<>>. Erasing from the end was very + // costly because we need to return the iterator following the erased + // one, as the hashtable is getting emptier at each step there are + // more and more empty bucket to loop through to reach the end of the + // container and find out that it was in fact the last element. + for (int j = nb - 1; j >= 0; --j) + { + auto it = us.find(j); + if (it != us.end()) + us.erase(it); + } - time_counter time; - resource_counter resource; + stop_counters(time, resource); + ostr.str(""); + ostr << desc << ": erase from iterator"; + report_performance(__FILE__, ostr.str().c_str(), time, resource); - start_counters(time, resource); + start_counters(time, resource); - std::unordered_set<int> us; - for (int i = 0; i != 5000000; ++i) - us.insert(i); + // This is a worst insertion use case for the current implementation as + // we insert an element at the begining of the hashtable and then we + // insert starting at the end so that each time we need to seek up to the + // first bucket to find the first non-empty one. + us.insert(0); + for (int i = nb - 1; i >= 0; --i) + us.insert(i); - stop_counters(time, resource); - report_performance(__FILE__, "Container generation", time, resource); + stop_counters(time, resource); + ostr.str(""); + ostr << desc << ": second insert"; + report_performance(__FILE__, ostr.str().c_str(), time, resource); - start_counters(time, resource); + start_counters(time, resource); - for (int j = 100; j != 0; --j) + for (int j = nb - 1; j >= 0; --j) + us.erase(j); + + stop_counters(time, resource); + ostr.str(""); + ostr << desc << ": erase from key"; + report_performance(__FILE__, ostr.str().c_str(), time, resource); + } + + // Bench using unordered_set<string> that show how important it is to cache + // hash code as computing string hash code is quite expensive compared to + // computing it for int. + template<bool use_cache> + void bench_str() { - auto it = us.begin(); - while (it != us.end()) + using namespace __gnu_test; + std::ostringstream ostr; + ostr << "unordered_set<string> " << (use_cache ? "with" : "without") + << " cache"; + const std::string desc = ostr.str(); + + time_counter time; + resource_counter resource; + + const int nb = 200000; + // First generate once strings that are going to be used throughout the + // bench: + std::vector<std::string> strs; + strs.reserve(nb); + for (int i = 0; i != nb; ++i) + { + ostr.str(""); + ostr << "string #" << i; + strs.push_back(ostr.str()); + } + + start_counters(time, resource); + + std::__unordered_set<std::string, std::hash<std::string>, + std::equal_to<std::string>, + std::allocator<std::string>, use_cache> us; + for (int i = 0; i != nb; ++i) + us.insert(strs[i]); + + stop_counters(time, resource); + ostr.str(""); + ostr << desc << ": first insert"; + report_performance(__FILE__, ostr.str().c_str(), time, resource); + + start_counters(time, resource); + + for (int j = nb - 1; j >= 0; --j) { - if ((*it % j) == 0) - it = us.erase(it); - else - ++it; + auto it = us.find(strs[j]); + if (it != us.end()) + us.erase(it); } - } - stop_counters(time, resource); - report_performance(__FILE__, "Container erase", time, resource); + stop_counters(time, resource); + ostr.str(""); + ostr << desc << ": erase from iterator"; + report_performance(__FILE__, ostr.str().c_str(), time, resource); - start_counters(time, resource); + start_counters(time, resource); - us.insert(0); + us.insert(strs[0]); + for (int i = nb - 1; i >= 0; --i) + us.insert(strs[i]); - for (int i = 0; i != 500; ++i) - { - auto it = us.begin(); - ++it; - assert( it == us.end() ); - } + stop_counters(time, resource); + ostr.str(""); + ostr << desc << ": second insert"; + report_performance(__FILE__, ostr.str().c_str(), time, resource); + + start_counters(time, resource); + + for (int j = nb - 1; j >= 0; --j) + us.erase(strs[j]); - stop_counters(time, resource); - report_performance(__FILE__, "Container iteration", time, resource); + stop_counters(time, resource); + ostr.str(""); + ostr << desc << ": erase from key"; + report_performance(__FILE__, ostr.str().c_str(), time, resource); + } +} +int main() +{ + bench<false>(); + bench<true>(); + bench_str<false>(); + bench_str<true>(); return 0; } |