llama : fix quantize with dl backends (ggml-org#13539)

Author: slaren

src/llama-model-loader.cpp

@@ -822,13 +822,18 @@ void llama_model_loader::init_mappings(bool prefetch, llama_mlocks * mlock_mmaps
         mappings.reserve(files.size());
         mmaps_used.reserve(files.size());
         for (const auto & file : files) {
-            auto * reg = ggml_backend_dev_backend_reg(ggml_backend_dev_by_type(GGML_BACKEND_DEVICE_TYPE_CPU));
-            if (!reg) {
-                throw std::runtime_error(format("%s: no CPU backend found", __func__));
+            bool is_numa = false;
+
+            auto * dev = ggml_backend_dev_by_type(GGML_BACKEND_DEVICE_TYPE_CPU);
+            if (dev) {
+                auto * reg = ggml_backend_dev_backend_reg(dev);
+                auto * is_numa_fn = (decltype(ggml_is_numa) *) ggml_backend_reg_get_proc_address(reg, "ggml_backend_cpu_is_numa");
+                if (is_numa_fn) {
+                    is_numa = is_numa_fn();
+                }
             }
 
-            auto * is_numa_fn = (decltype(ggml_is_numa) *) ggml_backend_reg_get_proc_address(reg, "ggml_backend_cpu_is_numa");
-            std::unique_ptr<llama_mmap> mapping = std::make_unique<llama_mmap>(file.get(), prefetch ? -1 : 0, is_numa_fn());
+            std::unique_ptr<llama_mmap> mapping = std::make_unique<llama_mmap>(file.get(), prefetch ? -1 : 0, is_numa);
             mmaps_used.emplace_back(mapping->size(), 0);
             if (mlock_mmaps) {
                 std::unique_ptr<llama_mlock> mlock_mmap(new llama_mlock());