From: Diego Devesa <redacted>
Date: Sun, 31 Aug 2025 13:49:03 +0000 (-0700)
Subject: llama : separate compute buffer reserve from fattn check (llama/15696)
X-Git-Tag: v0.9.1~119
X-Git-Url: https://git.djapps.eu/?a=commitdiff_plain;h=319bf932319ab96617ffa7ea93c5be2574edbdb0;p=pkg%2Fggml%2Fsources%2Fggml

llama : separate compute buffer reserve from fattn check (llama/15696)

Exposes ggml_backend_sched_split_graph() to allow splitting the graph without allocating compute buffers and uses it to split the graph for the automatic Flash Attention check.
---

diff --git a/include/ggml-backend.h b/include/ggml-backend.h
index a2977ea2..4f246f6c 100644
--- a/include/ggml-backend.h
+++ b/include/ggml-backend.h
@@ -307,6 +307,9 @@ extern "C" {
     GGML_API void                 ggml_backend_sched_set_tensor_backend(ggml_backend_sched_t sched, struct ggml_tensor * node, ggml_backend_t backend);
     GGML_API ggml_backend_t       ggml_backend_sched_get_tensor_backend(ggml_backend_sched_t sched, struct ggml_tensor * node);
 
+    // Split graph without allocating it
+    GGML_API void                 ggml_backend_sched_split_graph(ggml_backend_sched_t sched, struct ggml_cgraph * graph);
+
     // Allocate and compute graph on the backend scheduler
     GGML_API bool                 ggml_backend_sched_alloc_graph(ggml_backend_sched_t sched, struct ggml_cgraph * graph); // returns success
     GGML_API enum ggml_status     ggml_backend_sched_graph_compute(ggml_backend_sched_t sched, struct ggml_cgraph * graph);
diff --git a/src/ggml-backend.cpp b/src/ggml-backend.cpp
index 02375337..0cdbf180 100644
--- a/src/ggml-backend.cpp
+++ b/src/ggml-backend.cpp
@@ -902,7 +902,7 @@ static void ggml_backend_sched_set_if_supported(ggml_backend_sched_t sched, stru
 }
 
 // assigns backends to ops and splits the graph into subgraphs that can be computed on the same backend
-static void ggml_backend_sched_split_graph(ggml_backend_sched_t sched, struct ggml_cgraph * graph) {
+void ggml_backend_sched_split_graph(ggml_backend_sched_t sched, struct ggml_cgraph * graph) {
     // reset splits
     sched->n_splits = 0;
     sched->n_graph_inputs = 0;
@@ -1687,6 +1687,8 @@ bool ggml_backend_sched_reserve(ggml_backend_sched_t sched, struct ggml_cgraph *
     GGML_ASSERT(sched);
     GGML_ASSERT((int)sched->hash_set.size >= measure_graph->n_nodes + measure_graph->n_leafs);
 
+    ggml_backend_sched_reset(sched);
+
     ggml_backend_sched_synchronize(sched);
 
     ggml_backend_sched_split_graph(sched, measure_graph);