Use pow-of-4

Author: lowener

cpp/src/neighbors/ivf_flat/ivf_flat_interleaved_scan.cuh

@@ -1196,8 +1196,6 @@ void launch_with_fixed_consts(cuvs::distance::DistanceType metric, Args&&... arg
   }
 }
 
-#define BASE_CAPACITY 8u
-
 /**
  * Lift the `capacity` and `veclen` parameters to the template level,
  * forward the rest of the arguments unmodified to `launch_interleaved_scan_kernel`.
@@ -1224,7 +1222,7 @@ struct select_interleaved_scan_kernel {
           k_max, veclen, select_min, std::forward<Args>(args)...);
       }
     }
-    if constexpr (Capacity > BASE_CAPACITY) {
+    if constexpr (Capacity > 1) {
       if (k_max * 2 <= Capacity) {
         return select_interleaved_scan_kernel<T,
                                               AccT,
@@ -1334,7 +1332,7 @@ void ivfflat_interleaved_scan(const index<T, IdxT>& index,
                               uint32_t& grid_dim_x,
                               rmm::cuda_stream_view stream)
 {
-  const int capacity = std::max(BASE_CAPACITY, bound_by_power_of_two(k));
+  const int capacity = bound_by_power_of_four(k);
 
   auto filter_adapter = cuvs::neighbors::filtering::ivf_to_sample_filter(
     index.inds_ptrs().data_handle(), sample_filter);