From dda18100cde9b4e78a14e64ee9afb8f1e74b8140 Mon Sep 17 00:00:00 2001
From: Tarang Jain <tarangj@nvidia.com>
Date: Tue, 23 Apr 2024 17:15:01 -0700
Subject: [PATCH] make helper static

---
 cpp/include/raft/neighbors/cagra.cuh              |  3 +--
 .../raft/neighbors/detail/cagra/cagra_build.cuh   |  5 +----
 cpp/include/raft/neighbors/ivf_pq_types.hpp       | 15 +++++++++------
 cpp/test/neighbors/ann_cagra.cuh                  |  3 +--
 4 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/cpp/include/raft/neighbors/cagra.cuh b/cpp/include/raft/neighbors/cagra.cuh
index 8fbd8e6ee6..c4406b66c5 100644
--- a/cpp/include/raft/neighbors/cagra.cuh
+++ b/cpp/include/raft/neighbors/cagra.cuh
@@ -55,8 +55,7 @@ namespace raft::neighbors::cagra {
  * @code{.cpp}
  *   using namespace raft::neighbors;
  *   // use default index parameters
- *   ivf_pq::index_params build_params;
- *   build_params.initialize_from_dataset(dataset);
+ *   ivf_pq::index_params build_params = ivf_pq::index_params::from_dataset(dataset);
  *   ivf_pq::search_params search_params;
  *   auto knn_graph      = raft::make_host_matrix<IdxT, IdxT>(dataset.extent(0), 128);
  *   // create knn graph
diff --git a/cpp/include/raft/neighbors/detail/cagra/cagra_build.cuh b/cpp/include/raft/neighbors/detail/cagra/cagra_build.cuh
index fad720a03b..f6bb0bf8fe 100644
--- a/cpp/include/raft/neighbors/detail/cagra/cagra_build.cuh
+++ b/cpp/include/raft/neighbors/detail/cagra/cagra_build.cuh
@@ -59,10 +59,7 @@ void build_knn_graph(raft::resources const& res,
                                                             size_t(dataset.extent(1)),
                                                             node_degree);
 
-  if (!build_params) {
-    build_params = ivf_pq::index_params{};
-    build_params.value().initialize_from_dataset(dataset);
-  }
+  if (!build_params) { build_params = ivf_pq::index_params::from_dataset(dataset); }
 
   // Make model name
   const std::string model_name = [&]() {
diff --git a/cpp/include/raft/neighbors/ivf_pq_types.hpp b/cpp/include/raft/neighbors/ivf_pq_types.hpp
index 5a3e6caa24..b590776222 100644
--- a/cpp/include/raft/neighbors/ivf_pq_types.hpp
+++ b/cpp/include/raft/neighbors/ivf_pq_types.hpp
@@ -109,16 +109,19 @@ struct index_params : ann::index_params {
    * Helper that sets values according to the extents of the dataset mdspan.
    */
   template <typename DataT, typename Accessor>
-  void initialize_from_dataset(
+  static index_params from_dataset(
     mdspan<const DataT, matrix_extent<int64_t>, row_major, Accessor> dataset,
     raft::distance::DistanceType metric = raft::distance::L2Expanded)
   {
-    n_lists =
+    index_params params;
+    params.n_lists =
       dataset.extent(0) < 4 * 2500 ? 4 : static_cast<uint32_t>(std::sqrt(dataset.extent(0)));
-    pq_dim  = round_up_safe(static_cast<uint32_t>(dataset.extent(1) / 4), static_cast<uint32_t>(8));
-    pq_bits = 8;
-    kmeans_trainset_fraction = dataset.extent(0) < 10000 ? 1 : 0.1;
-    this->metric             = metric;
+    params.pq_dim =
+      round_up_safe(static_cast<uint32_t>(dataset.extent(1) / 4), static_cast<uint32_t>(8));
+    params.pq_bits                  = 8;
+    params.kmeans_trainset_fraction = dataset.extent(0) < 10000 ? 1 : 0.1;
+    params.metric                   = metric;
+    return params;
   }
 };
 
diff --git a/cpp/test/neighbors/ann_cagra.cuh b/cpp/test/neighbors/ann_cagra.cuh
index 499abd7e26..715a94403f 100644
--- a/cpp/test/neighbors/ann_cagra.cuh
+++ b/cpp/test/neighbors/ann_cagra.cuh
@@ -417,8 +417,7 @@ class AnnCagraSortTest : public ::testing::TestWithParam<AnnCagraInputs> {
         raft::make_host_matrix<IdxT, int64_t>(ps.n_rows, index_params.intermediate_graph_degree);
 
       if (ps.build_algo == graph_build_algo::IVF_PQ) {
-        auto build_params = ivf_pq::index_params{};
-        build_params.initialize_from_dataset(database_view, ps.metric);
+        auto build_params = ivf_pq::index_params::from_dataset(database_view, ps.metric);
         if (ps.host_dataset) {
           cagra::build_knn_graph<DataT, IdxT>(
             handle_, database_host_view, knn_graph.view(), 2, build_params);