Add initial thread pipeline benchmark

benchmarks/bench_thread_pipeline.cpp

@@ -0,0 +1,93 @@
+#include "thread_pipeline.hpp"
+
+#include <latch>
+#include <nanobench.h>
+#include <thread>
+#include <vector>
+
+int main() {
+  {
+    constexpr int LOG_PIPELINE_SIZE = 10; // 2^10 = 1024 slots
+    constexpr int NUM_ITEMS = 100'000;
+    constexpr int BATCH_SIZE = 16;
+    constexpr int BUSY_ITERS = 100;
+
+    auto bench = ankerl::nanobench::Bench()
+                     .title("Pipeline Throughput")
+                     .unit("item")
+                     .batch(NUM_ITEMS)
+                     .relative(true)
+                     .warmup(100);
+    bench.run("Zero stage pipeline", [&] {
+      for (int i = 0; i < NUM_ITEMS; ++i) {
+        for (volatile int i = 0; i < BUSY_ITERS; i = i + 1) {
+        }
+      }
+    });
+
+    std::vector<int> threads_per_stage = {1};
+    ThreadPipeline<std::latch *> pipeline(LOG_PIPELINE_SIZE, threads_per_stage);
+
+    std::latch done{0};
+
+    // Stage 0 consumer thread
+    std::thread stage0_thread([&pipeline, &done]() {
+      const int stage = 0;
+      const int thread_id = 0;
+
+      for (;;) {
+        auto guard = pipeline.acquire(stage, thread_id);
+
+        for (auto &item : guard.batch) {
+          for (volatile int i = 0; i < BUSY_ITERS; i = i + 1) {
+          }
+          if (item == &done) {
+            return;
+          }
+          if (item) {
+            item->count_down();
+          }
+        }
+      }
+    });
+
+    bench.run("One stage pipeline", [&] {
+      // Producer (main thread)
+      int items_pushed = 0;
+      while (items_pushed < NUM_ITEMS - 1) {
+        auto guard = pipeline.push(
+            std::min(NUM_ITEMS - 1 - items_pushed, BATCH_SIZE), true);
+
+        auto it = guard.batch.begin();
+        items_pushed += guard.batch.size();
+        for (size_t i = 0; i < guard.batch.size(); ++i, ++it) {
+          *it = nullptr;
+        }
+      }
+      std::latch finish{1};
+      {
+        auto guard = pipeline.push(1, true);
+        *guard.batch.begin() = &finish;
+      }
+      finish.wait();
+    });
+
+    {
+      auto guard = pipeline.push(1, true);
+      *guard.batch.begin() = &done;
+    }
+
+    stage0_thread.join();
+  }
+
+  // TODO: Add more benchmarks for:
+  // - Multi-stage pipelines (3+ stages)
+  // - Multiple threads per stage
+  // - Different batch sizes
+  // - Pipeline contention under load
+  // - Memory usage patterns
+  // - Latency measurements
+  // - Different wait strategies
+
+  return 0;
+}