Migrate to refs where possible

Author: bdice

cpp/include/rmm/mr/binning_memory_resource.hpp

@@ -154,7 +154,7 @@ class binning_memory_resource final : public device_memory_resource {
     } else if (resource_bins_.count(allocation_size) == 0) {  // do nothing if bin already exists
       owned_bin_resources_.push_back(
         std::make_unique<fixed_size_memory_resource<Upstream>>(upstream_mr_, allocation_size));
-      resource_bins_.insert({allocation_size, owned_bin_resources_.back().get()});
+      resource_bins_.insert({allocation_size, *owned_bin_resources_.back()});
     }
   }
 

cpp/include/rmm/mr/per_device_resource.hpp

@@ -105,7 +105,7 @@ namespace detail {
  *
  * @return Pointer to the static cuda_memory_resource used as the initial, default resource
  */
-RMM_EXPORT inline device_memory_resource* initial_resource()
+RMM_EXPORT inline cuda_memory_resource* initial_resource()
 {
   static cuda_memory_resource mr{};
   return &mr;
@@ -198,7 +198,7 @@ inline device_async_resource_ref set_per_device_resource_ref_unsafe(
   // Note: because resource_ref is not default-constructible, we can't use std::map::operator[]
   if (old_itr == map.end()) {
     map.insert({device_id.value(), new_resource_ref});
-    return device_async_resource_ref{detail::initial_resource()};
+    return device_async_resource_ref{*detail::initial_resource()};
   }
 
   auto old_resource_ref = old_itr->second;
@@ -244,7 +244,7 @@ inline device_memory_resource* set_per_device_resource(cuda_device_id device_id,
   // state consistent with the resource pointer state. This is necessary because the
   // Python API still uses the raw pointer API. Once the Python API is updated to use
   // resource_ref, this call can be removed.
-  detail::set_per_device_resource_ref_unsafe(device_id, new_mr);
+  if (new_mr != nullptr) { detail::set_per_device_resource_ref_unsafe(device_id, *new_mr); }
 
   auto& map          = detail::get_map();
   auto const old_itr = map.find(device_id.value());
@@ -338,7 +338,7 @@ inline device_async_resource_ref get_per_device_resource_ref(cuda_device_id devi
   // If a resource was never set for `id`, set to the initial resource
   auto const found = map.find(device_id.value());
   if (found == map.end()) {
-    auto item = map.insert({device_id.value(), detail::initial_resource()});
+    auto item = map.insert({device_id.value(), *detail::initial_resource()});
     return item.first->second;
   }
   return found->second;
@@ -447,7 +447,7 @@ inline device_async_resource_ref set_current_device_resource_ref(
  */
 inline device_async_resource_ref reset_per_device_resource_ref(cuda_device_id device_id)
 {
-  return set_per_device_resource_ref(device_id, detail::initial_resource());
+  return set_per_device_resource_ref(device_id, *detail::initial_resource());
 }
 
 /**