ggml: add graph_reused (ggml-org#21764)

* ggml: add graph_reused

* use versioning instead of reuse flag

* increment version with atomic

* use top bits for split numbering

* add assert

* move counter to ggml.c

* set uid in split_graph only

* fix windows

* address further review comments

* get next_uid rather than doing bit manipulation

* rename + add comment about uid

Author: am17an

ggml/src/ggml-backend.cpp

@@ -1030,6 +1030,8 @@ void ggml_backend_sched_split_graph(ggml_backend_sched_t sched, struct ggml_cgra
         GGML_ABORT("%s: failed to initialize context\n", __func__);
     }
 
+    graph->uid = ggml_graph_next_uid();
+
     // pass 1: assign backends to ops with pre-allocated inputs
     for (int i = 0; i < graph->n_leafs; i++) {
         struct ggml_tensor * leaf = graph->leafs[i];
@@ -1477,6 +1479,11 @@ void ggml_backend_sched_split_graph(ggml_backend_sched_t sched, struct ggml_cgra
         assert(graph_copy->size > graph_copy->n_leafs);
         graph_copy->leafs[graph_copy->n_leafs++] = leaf;
     }
+
+    // set ids for all splits
+    for (int i = 0; i < sched->n_splits; ++i) {
+        sched->splits[i].graph.uid = ggml_graph_next_uid();
+    }
 }
 
 static bool ggml_backend_sched_alloc_splits(ggml_backend_sched_t sched) {

ggml/src/ggml-cuda/common.cuh

@@ -1186,6 +1186,7 @@ struct ggml_cuda_graph {
     std::vector<cudaGraphNode_t> nodes;
     bool disable_due_to_gpu_arch = false;
     bool warmup_complete = false;
+    uint64_t uid = 0;
     struct node_properties {
         ggml_tensor node;
         void *   node_src_data_ptrs[GGML_MAX_SRC];

ggml/src/ggml-cuda/ggml-cuda.cu

@@ -3108,6 +3108,15 @@ static bool ggml_cuda_graph_update_required(ggml_backend_cuda_context * cuda_ctx
     const void * graph_key = ggml_cuda_graph_get_key(cgraph);
     ggml_cuda_graph * graph = cuda_ctx->cuda_graph(graph_key);
 
+    if (cgraph->uid != 0 &&
+        cgraph->uid == graph->uid) {
+        GGML_LOG_DEBUG("CUDA Graph id %zu reused\n", cgraph->uid);
+        GGML_ASSERT((int)graph->node_props.size() == cgraph->n_nodes);
+        return false;
+    }
+
+    graph->uid = cgraph->uid;
+
     // Check if the graph size has changed
     if ((int)graph->node_props.size() != cgraph->n_nodes) {
         res = true;

ggml/src/ggml-impl.h

@@ -30,6 +30,8 @@ extern "C" {
 
 void ggml_print_backtrace(void);
 
+uint64_t ggml_graph_next_uid(void);
+
 #ifndef MIN
 #    define MIN(a, b) ((a) < (b) ? (a) : (b))
 #endif
@@ -338,6 +340,10 @@ struct ggml_cgraph {
     struct ggml_hash_set visited_hash_set;
 
     enum ggml_cgraph_eval_order order;
+
+    // an optional identifier that can be utilized to recognize same graphs if two non-zero values match
+    // a value of 0 means it is not set and should be ignored
+    uint64_t uid;
 };
 
 // returns a slice of cgraph with nodes [i0, i1)

ggml/src/ggml.c

@@ -53,6 +53,16 @@
 
 #define UNUSED GGML_UNUSED
 
+uint64_t ggml_graph_next_uid(void) {
+#ifdef _MSC_VER
+    static volatile long long counter = 1;
+    return (uint64_t) _InterlockedIncrement64(&counter) - 1;
+#else
+    static uint64_t counter = 1;
+    return __atomic_fetch_add(&counter, 1, __ATOMIC_RELAXED);
+#endif
+}
+
 // Needed for ggml_fp32_to_bf16_row()
 #if defined(__AVX512BF16__)
 #if defined(_MSC_VER)
@@ -7098,6 +7108,7 @@ struct ggml_cgraph * ggml_new_graph_custom(struct ggml_context * ctx, size_t siz
         /*.use_counts   =*/ use_counts_ptr,
         /*.hash_table   =*/ { hash_size, hash_used, hash_keys_ptr },
         /*.order        =*/ GGML_CGRAPH_EVAL_ORDER_LEFT_TO_RIGHT,
+        /*.uid          =*/ 0,
     };
 
     ggml_hash_set_reset(&cgraph->visited_hash_set);
@@ -7125,6 +7136,7 @@ struct ggml_cgraph ggml_graph_view(struct ggml_cgraph * cgraph0, int i0, int i1)
         /*.use_counts       =*/ cgraph0->use_counts,
         /*.visited_hash_set =*/ cgraph0->visited_hash_set,
         /*.order            =*/ cgraph0->order,
+        /*.uid              =*/ 0
     };
 
     return cgraph;