05_16_05_threading_variants

Multi-Threaded Audio Processing Variants

Status: ⏸️ NOT STARTED Priority: HIGH (Critical Path) Dependencies: TAREA 0 (Variant Framework), TAREA 1 (SIMD Variants) Estimated Effort: 3-4 weeks

---

🎯 Purpose

Threading variants leverage multi-core CPUs to achieve N-core speedups for parallelizable operations. Modern CPUs have 8-32 cores, and threading can provide massive gains for independent operations like multi-voice synthesis, parallel filters, or multi-track mixing.

---

📋 Planned Features

1. Thread Pool Management

class ThreadPoolVariant : public IVariant {
public:
    ThreadPoolVariant(size_t numThreads = std::thread::hardware_concurrency());

    bool process(const float* input, float* output, size_t numSamples) override;

private:
    ThreadPool pool_;
    std::vector<std::future<void>> futures_;
};

2. Parallel Voice Processing

class ParallelVoiceVariant : public IVariant {
public:
    void processVoices(Voice** voices, int numVoices, float* output, size_t numSamples);
    // Each voice processed on separate thread

private:
    void processVoiceRange(Voice** voices, int start, int end, float* output);
};

Expected Speedup: 8-16x on 8-16 core CPUs

3. Lock-Free Processing

class LockFreeRingBuffer {
public:
    bool tryPush(const AudioBlock& block);
    bool tryPop(AudioBlock& block);

private:
    std::atomic<size_t> writeIndex_;
    std::atomic<size_t> readIndex_;
    AudioBlock* buffer_;
};

4. NUMA-Aware Processing

class NUMAThreadingVariant : public IVariant {
public:
    bool process(const float* input, float* output, size_t numSamples) override;
    // Binds threads to NUMA nodes

private:
    void bindToNUMANode(std::thread& t, int node);
};

---

📊 Performance Targets

Operation	Single-Thread	4-Thread	8-Thread	16-Thread
16 Voice Synth	50 ms	13 ms (3.8x)	7 ms (7.1x)	4 ms (12.5x)
32 Parallel Biquads	80 ms	21 ms (3.8x)	11 ms (7.3x)	6 ms (13.3x)
Multi-Track Mix (16)	40 ms	11 ms (3.6x)	6 ms (6.7x)	3.5 ms (11.4x)

Scalability: 80-85% efficiency (close to linear scaling)

---

🛠️ Implementation Plan

Week 1-2: Thread Pool Infrastructure - C++11 thread pool implementation - Work queue management - Task scheduling

Week 3: Parallel Algorithms - Parallel voice processing - Parallel filter banks - Multi-track mixing

Week 4: Advanced Features - Lock-free data structures - NUMA awareness - Thread pinning - Performance tuning

---

⚠️ Challenges

1. Overhead: Threading has overhead (~50-100µs per task)
2. Synchronization: Locks can cause contention
3. Cache Coherency: False sharing reduces performance
4. Real-Time: Thread scheduling is non-deterministic

---

✅ Success Criteria

• ✅ Near-linear scaling up to physical core count
• ✅ Lock-free critical paths
• ✅ <100µs overhead per parallel section
• ✅ Works on Windows, Linux, macOS

---

Status: ⏸️ Critical for multi-core utilization Priority: HIGH - Modern CPUs have 8-32 cores