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41975.cc: Add tests to check performance with or without cache of hash code and with...

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2011-11-06  François Dumont <fdumont@gcc.gnu.org>

	* testsuite/performance/23_containers/insert_erase/41975.cc: Add
	tests to check performance with or without cache of hash code and with
	string type that has a costlier hash functor than int type.

From-SVN: r181037
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François Dumont 2011-11-06 17:16:00 +00:00
parent 86951993f8
commit ba3aa0e6c7
2 changed files with 163 additions and 46 deletions
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6
libstdc++-v3/ChangeLog
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@ -1,3 +1,9 @@
2011-11-06 François Dumont <fdumont@gcc.gnu.org>
* testsuite/performance/23_containers/insert_erase/41975.cc: Add
tests to check performance with or without cache of hash code and with
string type that has a costlier hash functor than int type.
2011-11-06 Benjamin Kosnik <bkoz@redhat.com>
Andrew MacLeod <amacleod@redhat.com>

203
libstdc++-v3/testsuite/performance/23_containers/insert_erase/41975.cc
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@ -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>
namespace
{
// 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);
}
stop_counters(time, resource);
ostr.str("");
ostr << desc << ": erase from iterator";
report_performance(__FILE__, ostr.str().c_str(), time, resource);
start_counters(time, resource);
// 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);
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(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()
{
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)
{
auto it = us.find(strs[j]);
if (it != us.end())
us.erase(it);
}
stop_counters(time, resource);
ostr.str("");
ostr << desc << ": erase from iterator";
report_performance(__FILE__, ostr.str().c_str(), time, resource);
start_counters(time, resource);
us.insert(strs[0]);
for (int i = nb - 1; i >= 0; --i)
us.insert(strs[i]);
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);
ostr.str("");
ostr << desc << ": erase from key";
report_performance(__FILE__, ostr.str().c_str(), time, resource);
}
}
int main()
{
using namespace __gnu_test;
time_counter time;
resource_counter resource;
start_counters(time, resource);
std::unordered_set<int> us;
for (int i = 0; i != 5000000; ++i)
us.insert(i);
stop_counters(time, resource);
report_performance(__FILE__, "Container generation", time, resource);
start_counters(time, resource);
for (int j = 100; j != 0; --j)
{
auto it = us.begin();
while (it != us.end())
{
if ((*it % j) == 0)
it = us.erase(it);
else
++it;
}
}
stop_counters(time, resource);
report_performance(__FILE__, "Container erase", time, resource);
start_counters(time, resource);
us.insert(0);
for (int i = 0; i != 500; ++i)
{
auto it = us.begin();
++it;
assert( it == us.end() );
}
stop_counters(time, resource);
report_performance(__FILE__, "Container iteration", time, resource);
bench<false>();
bench<true>();
bench_str<false>();
bench_str<true>();
return 0;
}