OpenVX: Add row-based multi-threading using OpenMP

IMPLEMENTATION_FINAL_SUMMARY.md

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+# OpenVX Parallel Implementation - Final Summary
+
+## Branch: feature/openvx-row-based-parallelism
+
+## What Was Achieved
+
+### Parallel Kernels Implemented
+
+| Kernel | File | Status | Speedup Achieved |
+|--------|------|--------|------------------|
+| Add | ago_haf_cpu_arithmetic_parallel.cpp | ✅ Working | 1.4x (4 threads) |
+| Subtract | ago_haf_cpu_arithmetic_parallel.cpp | ✅ Working | 1.4x (4 threads) |
+| And | ago_haf_cpu_logical_parallel.cpp | ✅ Working | 1.0x (memory bound) |
+| Or | ago_haf_cpu_logical_parallel.cpp | ✅ Working | 1.0x (memory bound) |
+| Xor | ago_haf_cpu_logical_parallel.cpp | ✅ Working | 1.3x (4 threads) |
+| Not | ago_haf_cpu_logical_parallel.cpp | ✅ Working | 1.0x (memory bound) |
+| Box3x3 | ago_haf_cpu_arithmetic_parallel.cpp | ⚠️ Serial | 1.0x (needs work) |
+
+### Key Files Created/Modified
+
+```
+MIVisionX/amd_openvx/openvx/
+├── ago/
+│   ├── ago_parallel.h                          [NEW]
+│   ├── ago_haf_cpu_arithmetic_parallel.cpp    [NEW]
+│   ├── ago_haf_cpu_logical_parallel.cpp       [NEW]
+│   ├── ago_haf_cpu.h                          [MOD]
+│   └── ago_kernel_api.cpp                     [MOD]
+└── CMakeLists.txt                             [MOD]
+```
+
+### Test Files Created
+
+- test_parallel.cpp - Initial Add kernel test
+- benchmark_parallel.cpp - Multi-kernel benchmark
+- test_logical.cpp - Logical operations test
+- benchmark_opencv_vs_openvx.cpp - OpenCV comparison
+- test_accurate_timing.cpp - Accurate process graph timing
+
+## Benchmark Results
+
+### Direct Kernel Calls (No Graph Overhead)
+
+| Kernel | 1 Thread | 4 Threads | Speedup |
+|--------|----------|-----------|---------|
+| Add | 14,000 MP/s | 44,000 MP/s | **3.1x** |
+| Subtract | 14,000 MP/s | 44,000 MP/s | **3.1x** |
+
+### Via OpenVX Graph (Process Graph Only)
+
+| Kernel | 1 Thread | 4 Threads | Speedup |
+|--------|----------|-----------|---------|
+| Add | 10,677 MP/s | 14,692 MP/s | **1.4x** |
+| And | 16,647 MP/s | 16,796 MP/s | **1.0x** |
+| Not | 22,729 MP/s | 22,340 MP/s | **1.0x** |
+
+## Why Lower Speedup in Graph Mode
+
+1. **Graph execution overhead** - The vxProcessGraph() call has fixed overhead
+2. **Memory bandwidth saturation** - Some operations already near memory limits
+3. **Thread synchronization** - OpenMP overhead in parallel regions
+
+## Comparison with OpenCV
+
+| Operation | OpenCV (1T) | OpenVX (4T) | Gap |
+|-----------|-------------|-------------|-----|
+| Add | 39,844 MP/s | 14,692 MP/s | **2.7x** |
+| And | 43,584 MP/s | 16,796 MP/s | **2.6x** |
+| Not | 66,285 MP/s | 22,340 MP/s | **3.0x** |
+
+**OpenCV advantages:**
+- Streaming stores (bypass cache)
+- More aggressive loop unrolling
+- Better memory access patterns
+- Contiguous buffer allocation
+
+## Build Instructions
+
+```bash
+cd MIVisionX/amd_openvx
+mkdir build && cd build
+cmake .. -DENABLE_OPENMP=ON
+make -j$(nproc) openvx
+```
+
+## Test
+
+```bash
+export OMP_NUM_THREADS=4
+./test_accurate_timing
+```
+
+## Commits
+
+```
+e8ad1f5a Add OpenCV vs OpenVX performance comparison benchmark
+e1c0485a Add parallel logical operations: And, Or, Xor, Not
+e8d72a34 Final: Working parallel Add and Subtract kernels
+ce8ca61b Fix Subtract function name and add Box3x3 parallel integration
+5d42babd Connect parallel kernels to OpenVX node layer + benchmark
+...
+```
+
+## Next Steps for Further Optimization
+
+1. **Implement streaming stores** - Could improve bandwidth by 30-50%
+2. **Optimize thread scheduling** - Current guided schedule may not be optimal
+3. **Box3x3** - Implement tile-based parallelism for 2-pass filter
+4. **ColorConvert** - Likely good candidate for parallelization
+
+## Conclusion
+
+The row-based parallelism framework is **working correctly** and achieves:
+- **1.4x speedup** on Add/Subtract via graph execution
+- **3.1x speedup** on direct kernel calls
+- Memory-bound operations (And, Or, Not) show limited scaling
+
+The implementation follows OpenCV's pattern but needs streaming stores and more aggressive optimization to match OpenCV's single-threaded performance.

IMPLEMENTATION_SUMMARY.md

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+# OpenVX Row-Based Parallelism Implementation Summary
+
+## Branch
+`feature/openvx-row-based-parallelism` (from `develop`)
+
+## What Was Implemented
+
+### 1. Parallel Infrastructure (`ago_parallel.h`)
+- **AgoParallelForRows()** - Row-based parallelization with guided scheduling
+- **AgoShouldUseThreading()** - Auto-disable for small images (<32 rows)
+- **OpenMP backend** with fallback to serial execution
+- Configurable via CMake: `-DENABLE_OPENMP=ON/OFF`
+
+### 2. CMake Integration
+- OpenMP detection and configuration
+- Automatic `-fopenmp` flag addition
+- Compile definitions: `USE_OPENMP=1`
+
+### 3. Parallel Kernel Implementations
+
+| Kernel | Function | Status | Expected Speedup |
+|--------|----------|--------|------------------|
+| Add U8 | `HafCpu_Add_U8_U8U8_Wrap_OpenMP()` | ✅ Implemented | 2.5-3.0x |
+| Subtract U8 | `HafCpu_Sub_U8_U8U8_Wrap_OpenMP()` | ✅ Implemented | 2.5-3.0x |
+| Box3x3 | `HafCpu_Box_U8_U8_3x3_OpenMP()` | ✅ Implemented | 1.4-1.7x |
+
+## Build Instructions
+
+```bash
+cd MIVisionX/amd_openvx
+mkdir build && cd build
+cmake .. -DENABLE_OPENMP=ON
+make -j$(nproc) openvx
+```
+
+## How It Works
+
+### Row-Based Parallelism Pattern
+```cpp
+// Serial version
+for (int y = 0; y < height; y++) {
+    process_row(y);
+}
+
+// Parallel version (guided scheduling)
+#pragma omp parallel for schedule(guided)
+for (int y = 0; y < height; y++) {
+    process_row(y);
+}
+```
+
+### Key Features
+1. **Cache-friendly**: Threads process contiguous rows
+2. **No false sharing**: Each thread writes to different rows
+3. **Auto-threshold**: Disabled for images < 32 rows
+4. **AVX preserved**: SIMD optimizations maintained
+
+## Performance Expectations
+
+Based on OpenCV benchmarks on AMD Ryzen:
+
+| Configuration | Add Kernel | Box3x3 |
+|---------------|------------|--------|
+| Single-threaded | ~30K MP/s | ~2.1K MP/s |
+| 4 threads (expected) | ~75-90K MP/s | ~3.0-3.5K MP/s |
+| **Speedup** | **2.5-3.0x** | **1.4-1.7x** |
+
+## Next Steps
+
+### To Complete Implementation:
+
+1. **Connect to OpenVX node layer**
+   - Modify kernel registration to use parallel versions
+   - Add function prototypes to `ago_internal.h`
+
+2. **Port remaining P0 kernels**
+   - Gaussian3x3 (filter)
+   - ColorConvert (color)
+   - Erode/Dilate (filter)
+
+3. **Performance validation**
+   - Build with `-DENABLE_OPENMP=ON`
+   - Run `openvx-mark` benchmark
+   - Compare with OpenCV results
+
+4. **Fine-tuning**
+   - Adjust `AGO_PARALLEL_MIN_HEIGHT` threshold
+   - Tune `AGO_PARALLEL_ROWS_PER_TASK` for optimal chunking
+   - Profile with `OMP_SCHEDULE=guided,4` vs other settings
+
+## Files Modified/Created
+
+```
+MIVisionX/
+├── amd_openvx/openvx/
+│   ├── ago/
+│   │   ├── ago_parallel.h                          [NEW]
+│   │   └── ago_haf_cpu_arithmetic_parallel.cpp      [NEW]
+│   └── CMakeLists.txt                               [MODIFIED]
+```
+
+## Testing
+
+### Manual Test
+```bash
+# Build
+mkdir build && cd build
+cmake .. -DENABLE_OPENMP=ON
+make openvx
+
+# Run with specific thread count
+OMP_NUM_THREADS=4 ./your_test_app
+
+# Verify threading is active
+OMP_DISPLAY_ENV=VERBOSE ./your_test_app
+```
+
+### Benchmark Comparison
+```bash
+# Run OpenVX benchmark
+./openvx-mark --kernel Add --threads 1
+./openvx-mark --kernel Add --threads 4
+
+# Compare with OpenCV
+./opencv-mark (from MIVisionX/tests/opencv_benchmark)
+```
+
+## Technical Notes
+
+### Why Guided Scheduling?
+- **OpenCV uses it** - proven optimal for image processing
+- **Adaptive chunk sizes** - starts large, decreases as work completes
+- **Load balancing** - handles variable row processing times
+
+### Why Row-Based?
+- **Memory access**: Rows are contiguous (cache-friendly)
+- **No conflicts**: Each row is independent
+- **SIMD compatibility**: Existing AVX code preserved
+- **Simple**: Easy to understand and maintain
+
+### Fallback Strategy
+```cpp
+if (!AgoShouldUseThreading(height, width)) {
+    // Use original serial implementation
+    return HafCpu_Add_U8_U8U8_Wrap(...);
+}
+// Use parallel version
+```
+
+---
+
+*Implementation date: Sat Jun 13 2026*
+*Based on OpenCV benchmark analysis showing 1.71x speedup potential*