From bbe07554c50a5132009c6b3e66a4ecbf77c81e72 Mon Sep 17 00:00:00 2001
From: Allard Hendriksen <hendriksen.a.a@gmail.com>
Date: Thu, 12 Jan 2023 05:27:41 +0100
Subject: [PATCH] Add raft::void_op functor (#1136)

Follow up on PR #1049. Adds a void_op functor for lambdas that are unused.

Authors:
  - Allard Hendriksen (https://github.com/ahendriksen)

Approvers:
  - Louis Sugy (https://github.com/Nyrio)
  - Artem M. Chirkin (https://github.com/achirkin)
  - Corey J. Nolet (https://github.com/cjnolet)

URL: https://github.com/rapidsai/raft/pull/1136
---
 cpp/include/raft/core/operators.hpp            | 10 +++++++++-
 cpp/include/raft/distance/detail/canberra.cuh  |  8 ++------
 cpp/include/raft/distance/detail/chebyshev.cuh |  9 +++------
 cpp/include/raft/distance/detail/l1.cuh        |  8 ++------
 4 files changed, 16 insertions(+), 19 deletions(-)

diff --git a/cpp/include/raft/core/operators.hpp b/cpp/include/raft/core/operators.hpp
index de521cc945..398354df46 100644
--- a/cpp/include/raft/core/operators.hpp
+++ b/cpp/include/raft/core/operators.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, NVIDIA CORPORATION.
+ * Copyright (c) 2022-2023, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -40,6 +40,14 @@ struct identity_op {
   }
 };
 
+struct void_op {
+  template <typename... UnusedArgs>
+  constexpr RAFT_INLINE_FUNCTION void operator()(UnusedArgs...) const
+  {
+    return;
+  }
+};
+
 template <typename OutT>
 struct cast_op {
   template <typename InT, typename... UnusedArgs>
diff --git a/cpp/include/raft/distance/detail/canberra.cuh b/cpp/include/raft/distance/detail/canberra.cuh
index 90ed3940e1..43a904edba 100644
--- a/cpp/include/raft/distance/detail/canberra.cuh
+++ b/cpp/include/raft/distance/detail/canberra.cuh
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021-2022, NVIDIA CORPORATION.
+ * Copyright (c) 2021-2023, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -81,11 +81,7 @@ static void canberraImpl(const DataT* x,
   };
 
   // epilogue operation lambda for final value calculation
-  auto epilog_lambda = [] __device__(AccT acc[KPolicy::AccRowsPerTh][KPolicy::AccColsPerTh],
-                                     DataT * regxn,
-                                     DataT * regyn,
-                                     IdxT gridStrideX,
-                                     IdxT gridStrideY) { return; };
+  auto epilog_lambda = raft::void_op();
 
   if (isRowMajor) {
     auto canberraRowMajor = pairwiseDistanceMatKernel<false,
diff --git a/cpp/include/raft/distance/detail/chebyshev.cuh b/cpp/include/raft/distance/detail/chebyshev.cuh
index 454ee8c8bb..52573bd170 100644
--- a/cpp/include/raft/distance/detail/chebyshev.cuh
+++ b/cpp/include/raft/distance/detail/chebyshev.cuh
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021-2022, NVIDIA CORPORATION.
+ * Copyright (c) 2021-2023, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,6 +15,7 @@
  */
 
 #pragma once
+#include <raft/core/operators.hpp>
 #include <raft/distance/detail/pairwise_distance_base.cuh>
 
 namespace raft {
@@ -77,11 +78,7 @@ static void chebyshevImpl(const DataT* x,
   };
 
   // epilogue operation lambda for final value calculation
-  auto epilog_lambda = [] __device__(AccT acc[KPolicy::AccRowsPerTh][KPolicy::AccColsPerTh],
-                                     DataT * regxn,
-                                     DataT * regyn,
-                                     IdxT gridStrideX,
-                                     IdxT gridStrideY) { return; };
+  auto epilog_lambda = raft::void_op();
 
   if (isRowMajor) {
     auto chebyshevRowMajor = pairwiseDistanceMatKernel<false,
diff --git a/cpp/include/raft/distance/detail/l1.cuh b/cpp/include/raft/distance/detail/l1.cuh
index 95514db60b..87893bab7c 100644
--- a/cpp/include/raft/distance/detail/l1.cuh
+++ b/cpp/include/raft/distance/detail/l1.cuh
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2022, NVIDIA CORPORATION.
+ * Copyright (c) 2018-2023, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -76,11 +76,7 @@ static void l1Impl(const DataT* x,
   };
 
   // epilogue operation lambda for final value calculation
-  auto epilog_lambda = [] __device__(AccT acc[KPolicy::AccRowsPerTh][KPolicy::AccColsPerTh],
-                                     DataT * regxn,
-                                     DataT * regyn,
-                                     IdxT gridStrideX,
-                                     IdxT gridStrideY) { return; };
+  auto epilog_lambda = raft::void_op();
 
   if (isRowMajor) {
     auto l1RowMajor = pairwiseDistanceMatKernel<false,