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/************************************************************************
*
* Copyright (C) 2022-2024 IRCAD France
*
* This file is part of Sight.
*
* Sight is free software: you can redistribute it and/or modify it under
* the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Sight is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Sight. If not, see <https://www.gnu.org/licenses/>.
*
***********************************************************************/
#pragma once
#include <sight/utest/config.hpp>
#include <chrono>
#include <cmath>
#include <functional>
#include <numeric>
#include <optional>
/// @note std::source_location is not yet supported by clang...
/// Profile a function with multiple calls
#define SIGHT_PROFILE_FUNC(Func, ...) \
sight::utest::profile_func(SIGHT_SOURCE_FILE, __LINE__, Func __VA_OPT__( , ) __VA_ARGS__)
namespace sight::utest
{
//------------------------------------------------------------------------------
template<typename Func, typename Unit = std::chrono::milliseconds>
static inline std::tuple<Unit, Unit> profile_func(
const char* const _source,
const int _line,
Func _f,
std::size_t _iteration = 3,
const std::optional<std::string>& _label = std::nullopt,
const std::optional<double>& _target_ratio = std::nullopt
)
{
// Just to have at least one iteration
_iteration = std::max(std::size_t(1), _iteration);
std::vector<std::chrono::steady_clock::duration> durations;
durations.reserve(_iteration);
for(std::size_t i = 0 ; i < _iteration ; ++i)
{
// Register the current clock value
const auto& start = std::chrono::steady_clock::now();
// Execute the function
_f(i);
// Compute the elapsed time
durations.emplace_back(std::chrono::steady_clock::now() - start);
}
// Compute mean
const auto& mean = std::accumulate(
durations.begin(),
durations.end(),
std::chrono::steady_clock::duration()
) / durations.size();
// Compute variance
const double variance = std::accumulate(
durations.begin(),
durations.end(),
0.0,
[&](auto _a, const auto& _b)
{
const double diff = double(_b.count()) - double(mean.count());
return std::move(_a) + (diff * diff);
}) / double(durations.size());
// Compute standard error
const double standard_error = std::sqrt(variance);
using d_unit = std::chrono::duration<double, typename Unit::period>;
using d_duration = std::chrono::duration<double, typename std::chrono::steady_clock::duration::period>;
// Convert standard error to the same unit as "mean"
const auto converted_error = d_duration(standard_error);
// Convert standard error to double in the target unit
const double mean_as_double = std::chrono::duration_cast<d_unit>(mean).count();
const double error_as_double = std::chrono::duration_cast<d_unit>(converted_error).count();
bool accurate = true;
if(_target_ratio)
{
// Check if the standard error is not too big which means the measured time is not very accurate
const double error_ratio = error_as_double / mean_as_double;
accurate = error_ratio < *_target_ratio;
// Max 1000 iteration in "auto" mode...
if(!accurate && _iteration < 1000)
{
// Increase the number of iteration to have a more accurate result
_iteration *= 2;
std::cerr
<< "\nInaccurate results (error ratio = "
<< error_ratio
<< ") > (target ratio = "
<< *_target_ratio
<< "). Retrying with "
<< _iteration
<< " iterations."
<< std::endl;
return profile_func(_source, _line, _f, _iteration, _label, _target_ratio);
}
}
if(_label)
{
const auto unit = []
{
if constexpr(std::is_same_v<Unit, std::chrono::nanoseconds>)
{
return "ns";
}
if constexpr(std::is_same_v<Unit, std::chrono::microseconds>)
{
return "µs";
}
if constexpr(std::is_same_v<Unit, std::chrono::milliseconds>)
{
return "ms";
}
if constexpr(std::is_same_v<Unit, std::chrono::seconds>)
{
return "s";
}
if constexpr(std::is_same_v<Unit, std::chrono::minutes>)
{
return "min";
}
if constexpr(std::is_same_v<Unit, std::chrono::hours>)
{
return "h";
}
};
std::stringstream stream;
stream
<< *_label
<< " : average time ("
<< durations.size()
<< " iterations) = "
<< mean_as_double
<< " " << unit()
<< ", standard error = "
<< error_as_double
<< " " << unit()
<< (accurate || !_target_ratio ? "" : " - Not accurate !");
// We do not use macro because of __FILE__ and __LINE__
sight::core::log::g_logger.info(
stream.str(),
_source,
_line
);
}
return std::make_tuple(std::chrono::duration_cast<Unit>(mean), std::chrono::duration_cast<Unit>(converted_error));
}
} // namespace sight::utest
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