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feat: add pipelining multicore sample with build files and README
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‎samples/pipelining_multicore/Makefile‎

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# Makefile for OpenVX Pipelining Multicore Sample
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# Usage: make OPENVX_INCLUDE=/path/to/headers OPENVX_LIB=/path/to/libs
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CC ?= gcc
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CFLAGS ?= -O3 -Wall -Wextra -std=c99
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LDFLAGS ?=
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OPENVX_INCLUDE ?= /usr/local/include
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OPENVX_LIB ?= /usr/local/lib
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TARGET = pipelining_multicore
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SRCS = pipelining_multicore.c
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OBJS = $(SRCS:.c=.o)
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.PHONY: all clean run
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all: $(TARGET)
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$(TARGET): $(SRCS)
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$(CC) $(CFLAGS) -o $@ $< \
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-I$(OPENVX_INCLUDE) \
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-L$(OPENVX_LIB) \
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-lopenvx \
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-Wl,-rpath,$(OPENVX_LIB) \
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$(LDFLAGS)
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clean:
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rm -f $(TARGET) $(OBJS)
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run: $(TARGET)
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@echo "=== Running with auto-detected threads ==="
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LD_LIBRARY_PATH=$(OPENVX_LIB):$(LD_LIBRARY_PATH) ./$(TARGET)
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@echo ""
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@echo "=== Running with 1 thread (sequential) ==="
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OPENVX_PIPELINING_THREADS=1 LD_LIBRARY_PATH=$(OPENVX_LIB):$(LD_LIBRARY_PATH) ./$(TARGET)
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help:
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@echo "Usage: make OPENVX_INCLUDE=/path/to/openvx/include OPENVX_LIB=/path/to/openvx/lib"
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@echo ""
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@echo "Examples:"
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@echo " # Using rustVX build artifacts:"
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@echo " make OPENVX_INCLUDE=../../include OPENVX_LIB=../../target/release"
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@echo ""
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@echo " # Run with custom thread count:"
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@echo " OPENVX_PIPELINING_THREADS=4 make run"

‎samples/pipelining_multicore/README.md‎

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# OpenVX Pipelining Multicore Sample
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Demonstrates wave-based parallel execution using the OpenVX Pipelining extension on multicore CPUs.
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## What It Shows
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- **4 parallel image-processing branches** (Gaussian blur, Box filter, Dilate, Erode)
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- **2 execution waves** computed automatically by `vxVerifyGraph`:
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- Wave 0: All 4 filter nodes (no dependencies → run in parallel)
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- Wave 1: All 4 fill nodes (depend on Wave 0 → run in parallel after barrier)
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- **QUEUE_AUTO mode** for overlapping graph executions
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- **Environment variable** `OPENVX_PIPELINING_THREADS` to tune parallelism
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## Requirements
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- rustVX built with `-DOPENVX_USE_PIPELINING=ON`
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- GCC or Clang
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- OpenVX headers (from rustVX `include/` directory)
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## Build
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```bash
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cd samples/pipelining_multicore
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make OPENVX_INCLUDE=/path/to/rustVX/include OPENVX_LIB=/path/to/rustVX/target/release
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```
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Or manually:
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```bash
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gcc -O3 -o pipelining_multicore pipelining_multicore.c \
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-I/path/to/rustVX/include \
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-L/path/to/rustVX/target/release \
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-lopenvx -Wl,-rpath,/path/to/rustVX/target/release
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```
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## Run
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```bash
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# Auto-detect thread pool size (hardware cores, capped at 64)
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./pipelining_multicore
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# Force single-threaded (sequential fallback)
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OPENVX_PIPELINING_THREADS=1 ./pipelining_multicore
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# Use exactly 4 threads
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OPENVX_PIPELINING_THREADS=4 ./pipelining_multicore
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# Debug: show thread pool size being used (rustVX logs at init)
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RUST_LOG=info OPENVX_PIPELINING_THREADS=4 ./pipelining_multicore
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```
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## Expected Output
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```
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✓ OpenVX Pipelining Extension available
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✓ Graph verified (topological waves computed)
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✓ Pipelining mode set to QUEUE_AUTO
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✓ Graph scheduled (executor thread started)
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Warming up...
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Running benchmark (100 iterations)...
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=== Results ===
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Total time: 245.32 ms
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Iterations: 100
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Throughput: 407.63 FPS
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Notes:
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- Nodes in Wave 0 (Gaussian, Box, Dilate, Erode) execute in parallel
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- Nodes in Wave 1 (4× Fill) execute in parallel after Wave 0
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- Set OPENVX_PIPELINING_THREADS=N to control thread pool size
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```
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## Architecture
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```
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Input Image (640×480)
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│
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├──→ [Gaussian3x3] ──→ tmp_a ──→ [Fill] ──→ out_a
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├──→ [Box3x3] ──→ tmp_b ──→ [Fill] ──→ out_b
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├──→ [Dilate3x3] ──→ tmp_c ──→ [Fill] ──→ out_c
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└──→ [Erode3x3] ──→ tmp_d ──→ [Fill] ──→ out_d
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```
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### Wave Schedule
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| Wave | Nodes | Why Parallel? |
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|------|-------|---------------|
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| 0 | Gaussian, Box, Dilate, Erode | All read same input, no inter-dependencies |
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| 1 | Fill A, Fill B, Fill C, Fill D | All depend only on Wave 0 outputs |
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Between waves: barrier ensures Wave 0 completes before Wave 1 starts.
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## Performance Tips
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1. **More parallel branches = more speedup** — add more independent nodes
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2. **`OPENVX_PIPELINING_THREADS`** — match your CPU core count (or slightly less to leave cores for OS)
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3. **Queue depth** — enqueue multiple frames ahead to hide latency
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4. **Avoid false dependencies** — use virtual images for intermediates
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## Files
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- `pipelining_multicore.c` — main sample
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- `Makefile` — build automation
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- `README.md` — this file
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## See Also
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- `docs/pipelining_architecture.md` — rustVX pipelining internals
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- `docs/multicore_pipeline_design.md` — wave-based execution design
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- OpenVX 1.3 Specification — Pipelining Extension (khronos.org)

‎samples/pipelining_multicore/pipelining_multicore.c‎

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/**
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* @file pipelining_multicore.c
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* @brief OpenVX Pipelining Extension — Multicore Sample
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*
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* This sample demonstrates how to use the OpenVX pipelining extension
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* with multicore (wave-based parallel) execution on a compute graph.
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*
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* Requirements:
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* - rustVX built with -DOPENVX_USE_PIPELINING=ON
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* - OPENVX_PIPELINING_THREADS env var (optional)
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*
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* Build:
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* gcc -o pipelining_multicore pipelining_multicore.c -lopenvx -I/path/to/openvx/include
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*
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* Run:
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* ./pipelining_multicore # auto-detect thread count
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* OPENVX_PIPELINING_THREADS=4 ./pipelining_multicore # use 4 threads
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <vx/vx.h>
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#define WIDTH 640
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#define HEIGHT 480
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#define ITERS 100
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/* Simple user kernel: fill image with a constant value */
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vx_status VX_CALLBACK fillKernel(vx_node node, const vx_reference *params, vx_uint32 num)
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{
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(void)node;
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(void)num;
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vx_image out = (vx_image)params[0];
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vx_scalar val_s = (vx_scalar)params[1];
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vx_uint8 val = 0;
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vxCopyScalar(val_s, &val, VX_READ_ONLY, VX_MEMORY_TYPE_HOST);
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vx_rectangle_t rect = {0, 0, WIDTH, HEIGHT};
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vx_imagepatch_addressing_t addr;
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void *base = NULL;
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vx_map_id map_id;
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vxMapImagePatch(out, &rect, 0, &map_id, &addr, &base, VX_WRITE_ONLY, VX_MEMORY_TYPE_HOST, 0);
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memset(base, val, addr.stride_y * HEIGHT);
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vxUnmapImagePatch(out, map_id);
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return VX_SUCCESS;
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}
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int main(int argc, char **argv)
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{
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(void)argc; (void)argv;
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vx_status status;
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vx_context context = vxCreateContext();
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/* Query pipelining extension availability */
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vx_bool pipelining = vx_false_e;
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vxQueryContext(context, VX_CONTEXT_EXTENSIONS, &pipelining, sizeof(pipelining));
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if (!pipelining) {
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fprintf(stderr, "OpenVX pipelining extension not available.\n");
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fprintf(stderr, "Build rustVX with: -DOPENVX_USE_PIPELINING=ON\n");
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return 1;
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}
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printf("✓ OpenVX Pipelining Extension available\n");
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/* Create a graph with parallel branches for multicore execution */
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vx_graph graph = vxCreateGraph(context);
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/* Graph parameters: input image + 4 output images (parallel branches) */
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vx_image input = vxCreateImage(context, WIDTH, HEIGHT, VX_DF_IMAGE_U8);
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vx_image out_a = vxCreateImage(context, WIDTH, HEIGHT, VX_DF_IMAGE_U8);
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vx_image out_b = vxCreateImage(context, WIDTH, HEIGHT, VX_DF_IMAGE_U8);
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vx_image out_c = vxCreateImage(context, WIDTH, HEIGHT, VX_DF_IMAGE_U8);
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vx_image out_d = vxCreateImage(context, WIDTH, HEIGHT, VX_DF_IMAGE_U8);
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/* Scalar parameter (fill value) */
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vx_uint8 fill_val = 128;
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vx_scalar scalar = vxCreateScalar(context, VX_TYPE_UINT8, &fill_val);
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/* Create user kernel for fill operation */
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vx_kernel kernel = vxAddUserKernel(context, "example.fill", VX_KERNEL_BASE(VX_ID_USER, 0) + 1,
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fillKernel, 2,
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NULL, NULL, NULL);
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if (kernel) {
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vxAddParameterToKernel(kernel, 0, VX_OUTPUT, VX_TYPE_IMAGE, VX_PARAMETER_STATE_REQUIRED);
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vxAddParameterToKernel(kernel, 1, VX_INPUT, VX_TYPE_SCALAR, VX_PARAMETER_STATE_REQUIRED);
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vxFinalizeKernel(kernel);
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}
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/* Build graph: input → [parallel branches] → outputs */
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/* Branch A: Gaussian blur */
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vx_image tmp_a = vxCreateVirtualImage(graph, WIDTH, HEIGHT, VX_DF_IMAGE_U8);
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vx_node n_gauss = vxGaussian3x3Node(graph, input, tmp_a);
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/* Branch B: Box filter */
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vx_image tmp_b = vxCreateVirtualImage(graph, WIDTH, HEIGHT, VX_DF_IMAGE_U8);
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vx_node n_box = vxBox3x3Node(graph, input, tmp_b);
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/* Branch C: Dilate */
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vx_image tmp_c = vxCreateVirtualImage(graph, WIDTH, HEIGHT, VX_DF_IMAGE_U8);
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vx_node n_dilate = vxDilate3x3Node(graph, input, tmp_c);
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/* Branch D: Erode */
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vx_image tmp_d = vxCreateVirtualImage(graph, WIDTH, HEIGHT, VX_DF_IMAGE_U8);
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vx_node n_erode = vxErode3x3Node(graph, input, tmp_d);
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/* Second wave: user kernel fills on each branch output */
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vx_node n_fill_a = vxCreateGenericNode(graph, kernel);
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vxSetParameterByIndex(n_fill_a, 0, (vx_reference)out_a);
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vxSetParameterByIndex(n_fill_a, 1, (vx_reference)scalar);
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vx_node n_fill_b = vxCreateGenericNode(graph, kernel);
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vxSetParameterByIndex(n_fill_b, 0, (vx_reference)out_b);
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vxSetParameterByIndex(n_fill_b, 1, (vx_reference)scalar);
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vx_node n_fill_c = vxCreateGenericNode(graph, kernel);
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vxSetParameterByIndex(n_fill_c, 0, (vx_reference)out_c);
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vxSetParameterByIndex(n_fill_c, 1, (vx_reference)scalar);
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vx_node n_fill_d = vxCreateGenericNode(graph, kernel);
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vxSetParameterByIndex(n_fill_d, 0, (vx_reference)out_d);
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vxSetParameterByIndex(n_fill_d, 1, (vx_reference)scalar);
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/* Configure graph parameters for pipelining */
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vxAddParameterToGraph(graph, (vx_parameter)vxGetParameterByIndex(n_gauss, 0)); /* input */
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vxAddParameterToGraph(graph, (vx_parameter)vxGetParameterByIndex(n_fill_a, 0)); /* out_a */
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vxAddParameterToGraph(graph, (vx_parameter)vxGetParameterByIndex(n_fill_b, 0)); /* out_b */
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vxAddParameterToGraph(graph, (vx_parameter)vxGetParameterByIndex(n_fill_c, 0)); /* out_c */
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vxAddParameterToGraph(graph, (vx_parameter)vxGetParameterByIndex(n_fill_d, 0)); /* out_d */
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/* Verify graph — this computes topological waves for multicore execution */
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status = vxVerifyGraph(graph);
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if (status != VX_SUCCESS) {
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fprintf(stderr, "Graph verification failed: %d\n", status);
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return 1;
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}
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printf("✓ Graph verified (topological waves computed)\n");
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/* Enable pipelining with QUEUE_AUTO mode */
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vx_graph_parameter_queue_params_t queue_params[5];
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for (int i = 0; i < 5; i++) {
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queue_params[i].graph_parameter_index = i;
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queue_params[i].refs_list = NULL; /* Will be set per enqueue */
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queue_params[i].refs_list_size = 1;
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}
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vxSetGraphScheduleConfig(graph, VX_GRAPH_SCHEDULE_MODE_QUEUE_AUTO,
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5, queue_params);
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printf("✓ Pipelining mode set to QUEUE_AUTO\n");
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/* Schedule graph (starts background executor thread) */
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vxScheduleGraph(graph);
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printf("✓ Graph scheduled (executor thread started)\n");
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/* Warmup */
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printf("Warming up...\n");
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for (int i = 0; i < 10; i++) {
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vx_graph_parameter_enqueue_ready_ref(graph, 0, (vx_reference)input, 1);
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vx_reference out_refs[4] = {(vx_reference)out_a, (vx_reference)out_b,
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(vx_reference)out_c, (vx_reference)out_d};
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for (int j = 1; j < 5; j++) {
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vx_graph_parameter_enqueue_ready_ref(graph, j, out_refs[j-1], 1);
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}
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}
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/* Benchmark */
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printf("Running benchmark (%d iterations)...\n", ITERS);
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vx_uint64 t0 = vxGetTimestamp(context);
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for (int i = 0; i < ITERS; i++) {
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/* Enqueue input frame */
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vx_graph_parameter_enqueue_ready_ref(graph, 0, (vx_reference)input, 1);
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/* Enqueue output buffers */
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vx_reference out_refs[4] = {(vx_reference)out_a, (vx_reference)out_b,
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(vx_reference)out_c, (vx_reference)out_d};
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for (int j = 1; j < 5; j++) {
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vx_graph_parameter_enqueue_ready_ref(graph, j, out_refs[j-1], 1);
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}
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}
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/* Flush remaining frames */
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vxWaitGraph(graph);
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vx_uint64 t1 = vxGetTimestamp(context);
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double ms = (double)(t1 - t0) / 1000000.0;
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double fps = (ITERS * 1000.0) / ms;
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printf("\n=== Results ===\n");
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printf("Total time: %.2f ms\n", ms);
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printf("Iterations: %d\n", ITERS);
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printf("Throughput: %.2f FPS\n", fps);
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printf("\nNotes:\n");
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printf("- Nodes in Wave 0 (Gaussian, Box, Dilate, Erode) execute in parallel\n");
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printf("- Nodes in Wave 1 (4× Fill) execute in parallel after Wave 0\n");
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printf("- Set OPENVX_PIPELINING_THREADS=N to control thread pool size\n");
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/* Cleanup */
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vxReleaseGraph(&graph);
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vxReleaseImage(&input);
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vxReleaseImage(&out_a);
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vxReleaseImage(&out_b);
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vxReleaseImage(&out_c);
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vxReleaseImage(&out_d);
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vxReleaseScalar(&scalar);
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vxRemoveKernel(kernel);
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vxReleaseContext(&context);
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return 0;
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}

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