Aethera/kernel/src/kernel/frame_statistics.hpp

#pragma once
#include "frame.hpp"
#include <array>
#include <bitset>
#include <chrono>
#include <cstddef>
#include <cstdint>
#include <vector>

namespace aethera {
enum class Frame_Dimension : std::uint8_t { two_dimensional, three_dimensional };

enum class Frame_Statistic : std::uint8_t {
    plot_tick_queue_ms,
    plot_update_ms,
    plot_publish_ms,
    server_completion_ms,
    scene_render_ms,
    event_dispatch_ms,
    prepare_ms,
    paint_ms,
    backend_queue_ms,
    gpu_submission_ms,
    readback_stage_ms,
    callback_ms,
    backend_apply_ms,
    backend_plan_ms,
    backend_execute_ms,
    backend_submit_ms,
    gpu_fence_wait_ms,
    gpu_render_ms,
    gpu_transition_ms,
    gpu_copy_ms,
    gpu_total_ms,
    readback_ms,
    pipeline_2d_event_ms,
    pipeline_2d_prepare_ms,
    pipeline_2d_paint_ms,
    pipeline_2d_frame_target_ms,
    pipeline_2d_background_ms,
    pipeline_2d_cache_targets_ms,
    pipeline_2d_taskflow_ms,
    pipeline_2d_paint_coordination_ms,
    pipeline_2d_scene_coordination_ms,
    pipeline_2d_callback_ms,
    pipeline_2d_frame_handoff_ms,
    pipeline_3d_event_ms,
    pipeline_3d_prepare_ms,
    pipeline_3d_submit_graph_ms,
    pipeline_3d_scene_coordination_ms,
    pipeline_3d_prepare_queue_ms,
    pipeline_3d_backend_apply_ms,
    pipeline_3d_backend_plan_ms,
    pipeline_3d_backend_execute_ms,
    pipeline_3d_backend_commands_ms,
    pipeline_3d_backend_queue_ms,
    pipeline_3d_backend_submit_ms,
    pipeline_3d_submit_handoff_ms,
    pipeline_3d_gpu_render_ms,
    pipeline_3d_gpu_transition_ms,
    pipeline_3d_gpu_copy_ms,
    pipeline_3d_gpu_sync_ms,
    pipeline_3d_readback_ms,
    pipeline_3d_callback_ms,
    pipeline_3d_completion_handoff_ms,
    frame_interval_ms,
    count
};

inline constexpr std::size_t frame_statistic_count =
    static_cast<std::size_t>(Frame_Statistic::count);

struct Frame_Statistics_Sample {
    std::array<double, frame_statistic_count> values{};
    std::bitset<frame_statistic_count> present{};

    void set(Frame_Statistic statistic, double value) noexcept;
};

struct Statistic_State {
    std::size_t count{};
    double latest{};
    double minimum{};
    double maximum{};
    double average{};
    double trimmed_average{};
    double variability{};
    double p50{};
    double p95{};
    double p99{};
    bool operator==(const Statistic_State&) const = default;
};

class Sliding_Statistics final {
public:
    Sliding_Statistics();
    explicit Sliding_Statistics(std::size_t capacity);
    [[nodiscard]] Statistic_State submit(double value);
    [[nodiscard]] const Statistic_State& state() const noexcept;
    void reset() noexcept;

private:
    /* P² 只维护五个标记点，分位数是从 reset 起的在线估计，不保存样本。 */
    class Quantile_Estimator final {
    public:
        explicit Quantile_Estimator(double probability) noexcept;
        void submit(double value) noexcept;
        [[nodiscard]] double value() const noexcept;
        void reset() noexcept;
    private:
        double probability_{};
        std::array<double, 5> initial_{};
        std::array<double, 5> heights_{};
        std::array<double, 5> positions_{};
        std::array<double, 5> desired_{};
        std::array<double, 5> increments_{};
        std::size_t count_{};
    };

    /* 预分配单调队列，O(1) 摊还维护精确滑动窗口极值。 */
    class Extremum_Queue final {
    public:
        Extremum_Queue(std::size_t capacity, bool minimum);
        void submit(double value, std::uint64_t sequence,
                    std::size_t window) noexcept;
        [[nodiscard]] double value() const noexcept;
        void reset() noexcept;
    private:
        struct Node { double value{}; std::uint64_t sequence{}; };
        std::vector<Node> nodes_;
        std::size_t head_{};
        std::size_t tail_{};
        bool minimum_{};
    };

    /* 原始值和截尾值只为精确滑动均值/方差服务，构造后不再分配。 */
    std::vector<double> values_;
    std::vector<double> trimmed_values_;
    std::size_t size_{};
    std::size_t next_{};
    double sum_{};
    double squared_sum_{};
    double trimmed_sum_{};
    bool trimmed_window_initialized_{};
    std::uint64_t sequence_{};
    Extremum_Queue minimum_;
    Extremum_Queue maximum_;
    Quantile_Estimator p05_{0.05};
    Quantile_Estimator p50_{0.50};
    Quantile_Estimator p95_{0.95};
    Quantile_Estimator p99_{0.99};
    Statistic_State state_{};
};

struct Frame_Statistics_State {
    /* 可直接通过 Scene State 双缓冲发布的定长结果；不含统计器内部样本。 */
    std::array<Statistic_State, frame_statistic_count> values{};
    Frame_Identity identity{};
    std::uint64_t created_time_unix_ns{};
    std::uint64_t dropped_sequences{};
    bool operator==(const Frame_Statistics_State&) const = default;
};

class Frame_Statistics_Accumulator final {
public:
    explicit Frame_Statistics_Accumulator(std::size_t capacity = 600);
    [[nodiscard]] const Frame_Statistics_State& submit(
        const Render_Frame& frame, Frame_Dimension dimension);
    void reset() noexcept;
private:
    std::vector<Sliding_Statistics> values_;
    Frame_Statistics_State state_{};
    std::chrono::steady_clock::time_point previous_completion_{};
    std::uint64_t previous_sequence_{};
};
}