From bc524d70253a4ab2fe40c3ca3e5666e267c0a4d1 Mon Sep 17 00:00:00 2001
From: Lexi Winter <lexi@le-fay.org>
Date: Sun, 29 Jun 2025 19:25:29 +0100
Subject: import catch2 3.8.1

---
 .../benchmark/detail/catch_estimate_clock.hpp      | 127 +++++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 src/catch2/benchmark/detail/catch_estimate_clock.hpp

(limited to 'src/catch2/benchmark/detail/catch_estimate_clock.hpp')

diff --git a/src/catch2/benchmark/detail/catch_estimate_clock.hpp b/src/catch2/benchmark/detail/catch_estimate_clock.hpp
new file mode 100644
index 0000000..6da24ce
--- /dev/null
+++ b/src/catch2/benchmark/detail/catch_estimate_clock.hpp
@@ -0,0 +1,127 @@
+
+//              Copyright Catch2 Authors
+// Distributed under the Boost Software License, Version 1.0.
+//   (See accompanying file LICENSE.txt or copy at
+//        https://www.boost.org/LICENSE_1_0.txt)
+
+// SPDX-License-Identifier: BSL-1.0
+// Adapted from donated nonius code.
+
+#ifndef CATCH_ESTIMATE_CLOCK_HPP_INCLUDED
+#define CATCH_ESTIMATE_CLOCK_HPP_INCLUDED
+
+#include <catch2/benchmark/catch_clock.hpp>
+#include <catch2/benchmark/catch_environment.hpp>
+#include <catch2/benchmark/detail/catch_stats.hpp>
+#include <catch2/benchmark/detail/catch_measure.hpp>
+#include <catch2/benchmark/detail/catch_run_for_at_least.hpp>
+#include <catch2/benchmark/catch_clock.hpp>
+#include <catch2/internal/catch_unique_ptr.hpp>
+
+#include <algorithm>
+#include <vector>
+#include <cmath>
+
+namespace Catch {
+    namespace Benchmark {
+        namespace Detail {
+            template <typename Clock>
+            std::vector<double> resolution(int k) {
+                const size_t points = static_cast<size_t>( k + 1 );
+                // To avoid overhead from the branch inside vector::push_back,
+                // we allocate them all and then overwrite.
+                std::vector<TimePoint<Clock>> times(points);
+                for ( auto& time : times ) {
+                    time = Clock::now();
+                }
+
+                std::vector<double> deltas;
+                deltas.reserve(static_cast<size_t>(k));
+                for ( size_t idx = 1; idx < points; ++idx ) {
+                    deltas.push_back( static_cast<double>(
+                        ( times[idx] - times[idx - 1] ).count() ) );
+                }
+
+                return deltas;
+            }
+
+            constexpr auto warmup_iterations = 10000;
+            constexpr auto warmup_time = std::chrono::milliseconds(100);
+            constexpr auto minimum_ticks = 1000;
+            constexpr auto warmup_seed = 10000;
+            constexpr auto clock_resolution_estimation_time = std::chrono::milliseconds(500);
+            constexpr auto clock_cost_estimation_time_limit = std::chrono::seconds(1);
+            constexpr auto clock_cost_estimation_tick_limit = 100000;
+            constexpr auto clock_cost_estimation_time = std::chrono::milliseconds(10);
+            constexpr auto clock_cost_estimation_iterations = 10000;
+
+            template <typename Clock>
+            int warmup() {
+                return run_for_at_least<Clock>(warmup_time, warmup_seed, &resolution<Clock>)
+                    .iterations;
+            }
+            template <typename Clock>
+            EnvironmentEstimate estimate_clock_resolution(int iterations) {
+                auto r = run_for_at_least<Clock>(clock_resolution_estimation_time, iterations, &resolution<Clock>)
+                    .result;
+                return {
+                    FDuration(mean(r.data(), r.data() + r.size())),
+                    classify_outliers(r.data(), r.data() + r.size()),
+                };
+            }
+            template <typename Clock>
+            EnvironmentEstimate estimate_clock_cost(FDuration resolution) {
+                auto time_limit = (std::min)(
+                    resolution * clock_cost_estimation_tick_limit,
+                    FDuration(clock_cost_estimation_time_limit));
+                auto time_clock = [](int k) {
+                    return Detail::measure<Clock>([k] {
+                        for (int i = 0; i < k; ++i) {
+                            volatile auto ignored = Clock::now();
+                            (void)ignored;
+                        }
+                    }).elapsed;
+                };
+                time_clock(1);
+                int iters = clock_cost_estimation_iterations;
+                auto&& r = run_for_at_least<Clock>(clock_cost_estimation_time, iters, time_clock);
+                std::vector<double> times;
+                int nsamples = static_cast<int>(std::ceil(time_limit / r.elapsed));
+                times.reserve(static_cast<size_t>(nsamples));
+                for ( int s = 0; s < nsamples; ++s ) {
+                    times.push_back( static_cast<double>(
+                        ( time_clock( r.iterations ) / r.iterations )
+                            .count() ) );
+                }
+                return {
+                    FDuration(mean(times.data(), times.data() + times.size())),
+                    classify_outliers(times.data(), times.data() + times.size()),
+                };
+            }
+
+            template <typename Clock>
+            Environment measure_environment() {
+#if defined(__clang__)
+#    pragma clang diagnostic push
+#    pragma clang diagnostic ignored "-Wexit-time-destructors"
+#endif
+                static Catch::Detail::unique_ptr<Environment> env;
+#if defined(__clang__)
+#    pragma clang diagnostic pop
+#endif
+                if (env) {
+                    return *env;
+                }
+
+                auto iters = Detail::warmup<Clock>();
+                auto resolution = Detail::estimate_clock_resolution<Clock>(iters);
+                auto cost = Detail::estimate_clock_cost<Clock>(resolution.mean);
+
+                env = Catch::Detail::make_unique<Environment>( Environment{resolution, cost} );
+                return *env;
+            }
+        } // namespace Detail
+    } // namespace Benchmark
+} // namespace Catch
+
+#endif // CATCH_ESTIMATE_CLOCK_HPP_INCLUDED
-- 
cgit v1.2.3