From 1445a6b8487449c22f92e08c9ae1526c4bc55eb7 Mon Sep 17 00:00:00 2001
From: Allard Hendriksen <ahendriksen@nvidia.com>
Date: Wed, 11 Jan 2023 18:10:45 +0100
Subject: [PATCH] Add raft::no_op functor

This makes it easier to see if a lambda is unused.
---
 cpp/include/raft/core/operators.hpp            | 8 ++++++++
 cpp/include/raft/distance/detail/canberra.cuh  | 6 +-----
 cpp/include/raft/distance/detail/chebyshev.cuh | 7 ++-----
 cpp/include/raft/distance/detail/l1.cuh        | 6 +-----
 4 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/cpp/include/raft/core/operators.hpp b/cpp/include/raft/core/operators.hpp
index de521cc945..fae355a2a1 100644
--- a/cpp/include/raft/core/operators.hpp
+++ b/cpp/include/raft/core/operators.hpp
@@ -40,6 +40,14 @@ struct identity_op {
   }
 };
 
+struct no_op {
+  template <typename Type, typename... UnusedArgs>
+  constexpr RAFT_INLINE_FUNCTION void operator()(const Type& in, 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..9b5eb93a97 100644
--- a/cpp/include/raft/distance/detail/canberra.cuh
+++ b/cpp/include/raft/distance/detail/canberra.cuh
@@ -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::no_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..89ab0bf646 100644
--- a/cpp/include/raft/distance/detail/chebyshev.cuh
+++ b/cpp/include/raft/distance/detail/chebyshev.cuh
@@ -16,6 +16,7 @@
 
 #pragma once
 #include <raft/distance/detail/pairwise_distance_base.cuh>
+#include <raft/core/operators.hpp>
 
 namespace raft {
 namespace distance {
@@ -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::no_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..fad7ddca84 100644
--- a/cpp/include/raft/distance/detail/l1.cuh
+++ b/cpp/include/raft/distance/detail/l1.cuh
@@ -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::no_op();
 
   if (isRowMajor) {
     auto l1RowMajor = pairwiseDistanceMatKernel<false,