From a955d7c85a422334f71191bf1267c6b08bd53050 Mon Sep 17 00:00:00 2001
From: AlexanderSinn <alexander.sinn@desy.de>
Date: Tue, 23 Jan 2024 21:49:07 +0100
Subject: [PATCH] Add TypeList version of IdentityTuple to use it with
 ParReduce

---
 Src/Base/AMReX_Reduce.H | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Src/Base/AMReX_Reduce.H b/Src/Base/AMReX_Reduce.H
index 85710e7fc01..aa1a4dd0122 100644
--- a/Src/Base/AMReX_Reduce.H
+++ b/Src/Base/AMReX_Reduce.H
@@ -1289,6 +1289,20 @@ IdentityTuple (GpuTuple<Ts...>, ReduceOps<Ps...>) noexcept
     return r;
 }
 
+/**
+ * \brief Return a GpuTuple containing the identity element for each ReduceOp in TypeList.
+ * For example 0, +inf and -inf for ReduceOpSum, ReduceOpMin and ReduceOpMax respectively.
+ */
+template <typename... Ts, typename... Ps>
+AMREX_GPU_HOST_DEVICE
+constexpr GpuTuple<Ts...>
+IdentityTuple (GpuTuple<Ts...>, TypeList<Ps...>) noexcept
+{
+    GpuTuple<Ts...> r{};
+    Reduce::detail::for_each_init<0, decltype(r), Ps...>(r);
+    return r;
+}
+
 }
 
 #endif