KPN/examples/14_debug_hub/main.cpp

// Example 14 — DebugHub with Shared Resource Token
//
// Two independent KPN networks compete for one shared inference resource
// (simulating a small GPU or single-session ONNX runtime).  The DebugHub
// serves a single web UI at http://localhost:9090 with:
//
//   [All Networks]  — resource utilisation cards + cross-network node table
//   [detect]        — force-directed graph for the detection pipeline
//   [classify]      — force-directed graph for the classification pipeline
//
// Topology:
//
//   detect pipeline:
//     [source_detect] ──> [run_detect] ──> [sink_detect]
//
//   classify pipeline:
//     [source_classify] ──> [run_classify] ──> [sink_classify]
//
// Both [run_detect] and [run_classify] call gpu.acquire() before touching the
// simulated device.  The priority-based token awards the next slot to the
// waiter that is more likely to make useful progress (higher priority score).
//
// Build:  cmake -DKPN_WEB_DEBUG=ON ..  &&  cmake --build .
// Run:    ./14_debug_hub
// UI:     http://localhost:9090

#ifdef KPN_WEB_DEBUG

#include <kpn/kpn.hpp>

#include <atomic>
#include <chrono>
#include <iostream>
#include <thread>

using namespace kpn;
using namespace std::chrono_literals;

// ── Simulated inference device ────────────────────────────────────────────────
//
// Represents any exclusive, serialised accelerator: GPU session, ONNX runtime,
// hardware encoder, etc.  Only one caller can hold it at a time.

struct GPU {
    // Detection model: fast, 8 ms per frame.
    int detect(int frame_id) {
        std::this_thread::sleep_for(8ms);
        return frame_id * 2;           // synthetic "score"
    }

    // Classification model: heavier, 14 ms per frame.
    int classify(int frame_id) {
        std::this_thread::sleep_for(14ms);
        return frame_id % 10;          // synthetic "label"
    }
};

// Global pointer so free-function nodes can reach the resource.
// In production code, capture by reference inside an ObjectNode functor instead.
static SharedResource<GPU>* g_gpu = nullptr;

// ── Detection pipeline ────────────────────────────────────────────────────────

static int source_detect() {
    static std::atomic<int> id{0};
    std::this_thread::sleep_for(25ms);      // ~40 fps source rate
    return id.fetch_add(1, std::memory_order_relaxed);
}

static int run_detect(int frame_id) {
    // Higher priority: detection is latency-critical.
    auto guard = g_gpu->acquire([] { return 0.7f; });
    return guard->detect(frame_id);
}

static std::atomic<uint64_t> detect_out{0};
static void sink_detect(int) {
    detect_out.fetch_add(1, std::memory_order_relaxed);
}

// ── Classification pipeline ───────────────────────────────────────────────────

static int source_classify() {
    static std::atomic<int> id{0};
    std::this_thread::sleep_for(40ms);      // ~25 fps source rate
    return id.fetch_add(1, std::memory_order_relaxed);
}

static int run_classify(int frame_id) {
    // Lower priority: classification is best-effort.
    auto guard = g_gpu->acquire([] { return 0.3f; });
    return guard->classify(frame_id);
}

static std::atomic<uint64_t> classify_out{0};
static void sink_classify(int) {
    classify_out.fetch_add(1, std::memory_order_relaxed);
}

// ── main ──────────────────────────────────────────────────────────────────────

int main() {
    SharedResource<GPU> gpu;
    g_gpu = &gpu;

    // ── Detection network ─────────────────────────────────────────────────────
    auto src_det = make_node<source_detect, "source_detect">(4);
    auto inf_det = make_node<run_detect,    "run_detect"   >(4);
    auto snk_det = make_node<sink_detect,   "sink_detect"  >(4);

    auto net_detect = make_network(
        edge(src_det.output<0>(), inf_det.input<0>()),
        edge(inf_det.output<0>(), snk_det.input<0>())
    );

    // ── Classification network ────────────────────────────────────────────────
    auto src_cls = make_node<source_classify, "source_classify">(4);
    auto inf_cls = make_node<run_classify,    "run_classify"   >(4);
    auto snk_cls = make_node<sink_classify,   "sink_classify"  >(4);

    auto net_classify = make_network(
        edge(src_cls.output<0>(), inf_cls.input<0>()),
        edge(inf_cls.output<0>(), snk_cls.input<0>())
    );

    // ── Hub — one debug server for both networks + the shared resource ─────────
    DebugHub hub(9090);
    hub.register_network("detect",   net_detect);
    hub.register_network("classify", net_classify);
    hub.register_resource("gpu",     &gpu);

    net_detect.start();
    net_classify.start();
    hub.start();

    std::cout << "Running — open http://localhost:9090\n"
              << "Tabs: [All Networks]  [detect]  [classify]\n"
              << "Press Enter to stop.\n";
    std::cin.get();

    net_detect.stop();
    net_classify.stop();

    std::cout << "\nResults:\n"
              << "  detect:   " << detect_out.load()   << " frames\n"
              << "  classify: " << classify_out.load() << " frames\n";
    return 0;
}

#else  // no KPN_WEB_DEBUG

#include <iostream>
int main() {
    std::cerr << "This example requires KPN_WEB_DEBUG.\n"
              << "Rebuild with:  cmake -DKPN_WEB_DEBUG=ON ..\n";
    return 1;
}

#endif