Concurrency

Split the Hot Fields

Difficulty

Asked at Jump Trading, XTX Markets

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Language: C++23WorkerStats

#include <algorithm>
#include <array>
#include <atomic>
#include <cstddef>
#include <cstdint>
#include <memory>
#include <new>
#include <thread>
#include <vector>

// ...
// ...
// ...
// ...
// ...
struct ColdInfo {
    std::array<char, 16> name{};
    int cpu = 0;
};

// ...
// ...
// ...
// ...
// ...
struct PackedWorker {
    std::atomic<long long> processed{0};
    std::atomic<long long> dropped{0};
    std::atomic<long long> bytes{0};
    ColdInfo info;
};

// ...
inline long long line_of(const void* p) {
    return static_cast<long long>(reinterpret_cast<std::uintptr_t>(p) / 64);
}

// ...
// ...
// ...
// ...
// ...
// ...
class WorkerStats {
public:
    static constexpr std::size_t kLine = 64;

    explicit WorkerStats(std::size_t workers) : workers_(workers) {
        // ...
    }

    // ...
    void record(std::size_t w, long long processed, long long dropped, long long bytes) {
        // ...
        (void)w;
        (void)processed;
        (void)dropped;
        (void)bytes;
    }

    long long processed(std::size_t w) const {
        // ...
        (void)w;
        return 0;
    }

    long long dropped(std::size_t w) const {
        // ...
        (void)w;
        return 0;
    }

    long long bytes(std::size_t w) const {
        // ...
        (void)w;
        return 0;
    }

    long long total_processed() const {
        // ...
        return 0;
    }

    ColdInfo& info(std::size_t w) {
        // ...
        (void)w;
        static ColdInfo placeholder;
        return placeholder;
    }

    const ColdInfo& info(std::size_t w) const {
        // ...
        (void)w;
        static const ColdInfo placeholder;
        return placeholder;
    }

    // ...
    const void* hot_begin(std::size_t w) const {
        // ...
        (void)w;
        return nullptr;
    }

    const void* hot_end(std::size_t w) const {
        // ...
        (void)w;
        return nullptr;
    }

    // ...
    std::size_t cold_stride() const {
        // ...
        return 0;
    }

    std::size_t workers() const { return workers_; }

private:
    std::size_t workers_;
    // ...
};

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Split the Hot Fields

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