rpc : use graph uid instead of graph cache (ggml-org#22701)

Store the last graph uid and compare against it to determine if the same
graph is being computed.

Author: rgerganov

ggml/src/ggml-rpc/ggml-rpc.cpp

@@ -207,35 +207,11 @@ struct ggml_backend_rpc_buffer_type_context {
     size_t      max_size;
 };
 
-struct graph_cache {
-
-    bool is_cached(const ggml_cgraph * cgraph) {
-        if ((int)last_graph.size() != cgraph->n_nodes) {
-            return false;
-        }
-        for (int i = 0; i < cgraph->n_nodes; i++) {
-            if (memcmp(&last_graph[i], cgraph->nodes[i], sizeof(ggml_tensor)) != 0) {
-                return false;
-            }
-        }
-        return true;
-    }
-
-    void add(const ggml_cgraph * cgraph) {
-        last_graph.resize(cgraph->n_nodes);
-        for (int i = 0; i < cgraph->n_nodes; i++) {
-            memcpy(&last_graph[i], cgraph->nodes[i], sizeof(ggml_tensor));
-        }
-    }
-
-    std::vector<ggml_tensor> last_graph;
-};
-
 struct ggml_backend_rpc_context {
     std::string endpoint;
     uint32_t    device;
     std::string name;
-    graph_cache gc;
+    uint64_t    last_graph_uid;
 };
 
 struct ggml_backend_rpc_buffer_context {
@@ -717,15 +693,15 @@ static enum ggml_status ggml_backend_rpc_graph_compute(ggml_backend_t backend, g
     ggml_backend_rpc_context * rpc_ctx = (ggml_backend_rpc_context *)backend->context;
 
     GGML_ASSERT(cgraph->n_nodes > 0);
-    bool reuse = rpc_ctx->gc.is_cached(cgraph);
+    bool reuse = cgraph->uid != 0 && rpc_ctx->last_graph_uid == cgraph->uid;
     if (reuse) {
         rpc_msg_graph_recompute_req request;
         request.device = rpc_ctx->device;
         auto sock = get_socket(rpc_ctx->endpoint);
         bool status = send_rpc_cmd(sock, RPC_CMD_GRAPH_RECOMPUTE, &request, sizeof(request));
         RPC_STATUS_ASSERT(status);
     } else {
-        rpc_ctx->gc.add(cgraph);
+        rpc_ctx->last_graph_uid = cgraph->uid;
         std::vector<uint8_t> input;
         serialize_graph(rpc_ctx->device, cgraph, input);
         auto sock = get_socket(rpc_ctx->endpoint);
@@ -791,10 +767,10 @@ ggml_backend_buffer_type_t ggml_backend_rpc_buffer_type(const char * endpoint, u
 ggml_backend_t ggml_backend_rpc_init(const char * endpoint, uint32_t device) {
     std::string dev_name = "RPC" + std::to_string(device) + "[" + std::string(endpoint) + "]";
     ggml_backend_rpc_context * ctx = new ggml_backend_rpc_context {
-        /* .endpoint = */ endpoint,
-        /* .device   = */ device,
-        /* .name     = */ dev_name,
-        /* .gc       = */ {},
+        /* .endpoint       = */ endpoint,
+        /* .device         = */ device,
+        /* .name           = */ dev_name,
+        /* .last_graph_uid = */ 0,
     };
     auto reg = ggml_backend_rpc_add_server(endpoint);
     ggml_backend_t backend = new ggml_backend {