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benchmarks: synchronize threads before starting the benchmark

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This commit is contained in:
Mickey Rose 2016-02-28 00:28:00 +01:00
parent 02286bb7d1
commit db58b8b578
1 changed files with 35 additions and 22 deletions
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57
benchmark/bench_framework.hpp
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@ -187,20 +187,41 @@ int run(T const& test_runner, std::string const& name)
std::chrono::duration<double> min_seconds(*opt_min_duration);
auto min_duration = std::chrono::duration_cast<decltype(elapsed)>(min_seconds);
auto num_iters = test_runner.iterations();
auto num_threads = test_runner.threads();
auto total_iters = 0;
if (test_runner.threads() > 0)
if (num_threads > 0)
{
using thread_group = std::vector<std::unique_ptr<std::thread> >;
using value_type = thread_group::value_type;
thread_group tg;
for (std::size_t i=0;i<test_runner.threads();++i)
std::mutex mtx_ready;
std::unique_lock<std::mutex> lock_ready(mtx_ready);
auto stub = [&](T const& test_copy)
{
tg.emplace_back(new std::thread(test_runner));
// workers will wait on this mutex until the main thread
// constructs all of them and starts measuring time
std::unique_lock<std::mutex> my_lock(mtx_ready);
my_lock.unlock();
test_copy();
};
std::vector<std::thread> tg;
tg.reserve(num_threads);
for (auto i = num_threads; i-- > 0; )
{
tg.emplace_back(stub, test_runner);
}
start = std::chrono::high_resolution_clock::now();
std::for_each(tg.begin(), tg.end(), [](value_type & t) {if (t->joinable()) t->join();});
lock_ready.unlock();
// wait for all workers to finish
for (auto & t : tg)
{
if (t.joinable())
t.join();
}
elapsed = std::chrono::high_resolution_clock::now() - start;
// this is actually per-thread count, not total, but I think
// reporting average 'iters/thread/second' is more useful
// than 'iters/second' multiplied by the number of threads
total_iters += num_iters;
}
else
@ -215,27 +236,19 @@ int run(T const& test_runner, std::string const& name)
char msg[200];
double dur_total = milliseconds<double>(elapsed).count();
auto elapsed_nonzero = std::max(elapsed, decltype(elapsed){1});
big_number_fmt itersf(4, total_iters);
big_number_fmt ips(5, total_iters / seconds<double>(elapsed_nonzero).count());
std::snprintf(msg, sizeof(msg),
"%-43s %3zu threads %*.0f%s iters %6.0f milliseconds",
"%-43s %3zu threads %*.0f%s iters %6.0f milliseconds %*.0f%s i/s\n",
name.c_str(),
test_runner.threads(),
num_threads,
itersf.w, itersf.v, itersf.u,
dur_total);
dur_total,
ips.w, ips.v, ips.u
);
std::clog << msg;
// log average # of iterations per second, currently only for
// non-threaded runs
if (test_runner.threads() == 0)
{
auto elapsed_nonzero = std::max(elapsed, decltype(elapsed){1});
big_number_fmt ips(5, total_iters / seconds<double>(elapsed_nonzero).count());
std::snprintf(msg, sizeof(msg), " %*.0f%s i/s", ips.w, ips.v, ips.u);
std::clog << msg;
}
std::clog << "\n";
return 0;
}
catch (std::exception const& ex)