cont : clean-up recurrent memory

src/llama-memory-recurrent.cpp

@@ -125,6 +125,13 @@ llama_memory_recurrent::llama_memory_recurrent(
         ctxs_bufs.emplace_back(std::move(ctx), buf);
     }
 
+    if (is_empty()) {
+        if (n_rs_seq > 0) {
+            n_rs_seq = 0;
+            LLAMA_LOG_INFO("%s: disabling rollback snapshots because the memory module is empty\n", __func__);
+        }
+    }
+
     {
         const size_t memory_size_r = size_r_bytes();
         const size_t memory_size_s = size_s_bytes();
@@ -193,7 +200,7 @@ bool llama_memory_recurrent::seq_rm(llama_seq_id seq_id, llama_pos p0, llama_pos
             // partial rollback via per-token snapshot index (bounded by n_rs_seq)
             if (0 < p0 && p0 <= cell.pos && p1 > cell.pos) {
                 // the filter kept no layer (e.g. an MTP draft context), so only the position moves back
-                if (ctxs_bufs.empty()) {
+                if (is_empty()) {
                     cell.pos = p0 - 1;
                     return true;
                 }
@@ -723,6 +730,11 @@ bool llama_memory_recurrent::get_can_shift() const {
     return true;
 }
 
+bool llama_memory_recurrent::is_empty() const {
+    assert(total_size() == 0);
+    return ctxs_bufs.empty();
+}
+
 size_t llama_memory_recurrent::total_size() const {
     size_t size = 0;
     for (const auto & [_, buf] : ctxs_bufs) {

src/llama-memory-recurrent.h

@@ -123,6 +123,9 @@ private:
     // ggml contexts for the KV cache along with the allocated backend buffers:
     std::vector<std::pair<ggml_context_ptr, ggml_backend_buffer_ptr>> ctxs_bufs;
 
+    // true if no layers - can happen if the layer filter removes all layers
+    bool is_empty() const;
+
     size_t total_size() const;
 
     size_t size_r_bytes() const;