threads: add simple barrier test

This test does lots of small, parallel matmul ops where the barriers in between dominate the overhead.

tests/CMakeLists.txt

@@ -119,6 +119,7 @@ llama_target_and_test(test-grammar-parser.cpp)
 llama_target_and_test(test-llama-grammar.cpp)
 llama_target_and_test(test-grammar-integration.cpp)
 llama_target_and_test(test-grad0.cpp)
+llama_target_and_test(test-barrier.cpp)
 # llama_target_and_test(test-opt.cpp) # SLOW
 llama_target_and_test(test-backend-ops.cpp)
 

tests/test-barrier.cpp

@@ -0,0 +1,93 @@
+#include "ggml.h"
+#include "ggml-backend.h"
+
+#include <chrono>
+#include <iostream>
+#include <cstdio>
+#include <cstdlib>
+#include <cassert>
+#include <vector>
+
+#define MAX_NARGS 2
+
+int main(int argc, char *argv[]) {
+
+    int n_threads = 4;
+    int n_rounds  = 100;
+
+    if (argc > 1) {
+        n_threads = std::atoi(argv[1]);
+    }
+
+    if (argc > 2) {
+        n_rounds  = std::atoi(argv[2]);
+    }
+
+    struct ggml_init_params params = {
+        /* .mem_size   = */ 1024*1024*1024,
+        /* .mem_buffer = */ NULL,
+        /* .no_alloc   = */ false,
+    };
+
+    struct ggml_context * ctx = ggml_init(params);
+
+    // Create graph
+    struct ggml_cgraph * gf = ggml_new_graph(ctx);
+
+    // Lots of small, parallel ops where barriers in between will dominate
+    struct ggml_tensor * out = ggml_new_tensor_1d(ctx, GGML_TYPE_F32,  64);
+    for (int i = 0; i < 1000; i++) {
+        struct ggml_tensor * a = ggml_new_tensor_2d(ctx, GGML_TYPE_Q4_0, 64, 128);
+        out = ggml_mul_mat(ctx, a, out);
+
+        struct ggml_tensor * d = ggml_new_tensor_2d(ctx, GGML_TYPE_Q4_0, 128, 64);
+        out = ggml_mul_mat(ctx, d, out);
+    }
+
+    ggml_build_forward_expand(gf, out);
+    int n_nodes = ggml_graph_n_nodes(gf);
+
+    // Create threadpool
+    struct ggml_threadpool_params tpp  = ggml_threadpool_params_default(n_threads);
+    struct ggml_threadpool* threadpool = ggml_threadpool_new(&tpp);
+    if (!threadpool) {
+        fprintf(stderr, "threadpool create failed : n_threads %d\n", n_threads);
+        exit(1);
+    }
+
+    // Create compute plan
+    struct ggml_cplan cplan = ggml_graph_plan(gf, n_threads, threadpool);
+
+    std::vector<uint8_t> work_data(cplan.work_size);
+    cplan.work_data = work_data.data();
+
+    std::cerr << "graph-compute with"
+              << "\n n_threads: " << n_threads
+              << "\n   n_nodes: " << n_nodes
+              << "\n  n_rounds: " << n_rounds
+              << "\n";
+    // ggml_graph_print(gf);
+
+    // Warmup
+    ggml_graph_compute(gf, &cplan);
+
+    auto t0 = std::chrono::high_resolution_clock::now();
+
+    for (int i=0; i < n_rounds; i++) {
+        ggml_graph_compute(gf, &cplan);
+    }
+
+    auto t1 = std::chrono::high_resolution_clock::now();
+
+    auto usec = std::chrono::duration_cast<std::chrono::microseconds>(t1-t0).count();
+    auto nsec = std::chrono::duration_cast<std::chrono::nanoseconds>(t1-t0).count();
+    std::cerr << "graph-compute took " << usec << " usec "
+              << "\n " << (float) usec / n_rounds << " usec per-iter"
+              << "\n " << (float) nsec / (n_rounds * n_nodes) << " nsec per-node"
+              << "\n";
+
+    ggml_free(ctx);
+    ggml_threadpool_free(threadpool);
+
+    return 0;
+}