UPSTREAM PR #18547: context : reserve new scheduler when graph topology changes

common/common.cpp

@@ -1172,7 +1172,6 @@ common_init_result::common_init_result(common_params & params) :
         pimpl->samplers_seq_config[i] = { i, common_sampler_get(pimpl->samplers[i].get()) };
     }
 
-    // TODO: temporarily gated behind a flag
     if (params.sampling.backend_sampling) {
         cparams.samplers   = pimpl->samplers_seq_config.data();
         cparams.n_samplers = pimpl->samplers_seq_config.size();

common/sampling.cpp

@@ -334,15 +334,21 @@ struct common_sampler * common_sampler_init(const struct llama_model * model, st
 }
 
 void common_sampler_free(struct common_sampler * gsmpl) {
-    if (gsmpl) {
-        llama_sampler_free(gsmpl->grmr);
-        llama_sampler_free(gsmpl->chain);
-
-        delete gsmpl;
+    if (!gsmpl) {
+        return;
     }
+
+    llama_sampler_free(gsmpl->grmr);
+    llama_sampler_free(gsmpl->chain);
+
+    delete gsmpl;
 }
 
 void common_sampler_accept(struct common_sampler * gsmpl, llama_token token, bool accept_grammar) {
+    if (!gsmpl) {
+        return;
+    }
+
     const auto tm = gsmpl->tm();
 
     if (gsmpl->grmr && accept_grammar) {
@@ -355,6 +361,10 @@ void common_sampler_accept(struct common_sampler * gsmpl, llama_token token, boo
 }
 
 void common_sampler_reset(struct common_sampler * gsmpl) {
+    if (!gsmpl) {
+        return;
+    }
+
     gsmpl->reset();
 }
 
@@ -415,6 +425,10 @@ void common_perf_print(const struct llama_context * ctx, const struct common_sam
 }
 
 struct llama_sampler * common_sampler_get(const struct common_sampler * gsmpl) {
+    if (!gsmpl) {
+        return nullptr;
+    }
+
     return gsmpl->chain;
 }
 

examples/batched/batched.cpp

@@ -81,7 +81,6 @@ int main(int argc, char ** argv) {
         sampler_configs.push_back({ i, smpl });
     }
 
-    // TODO: temporarily gated behind a flag
     if (params.sampling.backend_sampling) {
         ctx_params.samplers   = sampler_configs.data();
         ctx_params.n_samplers = sampler_configs.size();

include/llama.h

@@ -1255,7 +1255,6 @@ extern "C" {
     // [EXPERIMENTAL]
     // attach a sampler to the context
     // note: prefer initializing the context with llama_context_params.samplers when possible
-    // note: changing the samplers of a context can cause graph reallocations and degraded performance
     LLAMA_API bool llama_set_sampler(struct llama_context * ctx, llama_seq_id seq_id, struct llama_sampler * smpl);
 
     // mirror of llama_sampler_i: