From 066c1b3ea394b40b46cf1e67f4dadecd33a3a531 Mon Sep 17 00:00:00 2001
From: Jonathan Lifflander <jliffla@sandia.gov>
Date: Thu, 27 Apr 2023 15:28:49 -0700
Subject: [PATCH] #276: reduce: reorder arguments for bare reduce to match

---
 examples/hello_world/hello_reduce.cc        |  2 +-
 src/vt/collective/reduce/get_reduce_stamp.h |  1 +
 src/vt/collective/reduce/reduce.h           | 32 +++++++++------------
 src/vt/collective/reduce/reduce.impl.h      | 14 +++++++++
 4 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/examples/hello_world/hello_reduce.cc b/examples/hello_world/hello_reduce.cc
index 46e4dd2170..69a11bee89 100644
--- a/examples/hello_world/hello_reduce.cc
+++ b/examples/hello_world/hello_reduce.cc
@@ -55,7 +55,7 @@ int main(int argc, char** argv) {
   vt::NodeType const root = 0;
 
   auto r = vt::theCollective()->global();
-  r->reduce<vt::collective::PlusOp, reduceResult>(vt::Node{root}, 50, 52.334);
+  r->reduce<reduceResult, vt::collective::PlusOp>(vt::Node{root}, 50, 52.334);
 
   vt::finalize();
   return 0;
diff --git a/src/vt/collective/reduce/get_reduce_stamp.h b/src/vt/collective/reduce/get_reduce_stamp.h
index 49a313ab9b..03032b2406 100644
--- a/src/vt/collective/reduce/get_reduce_stamp.h
+++ b/src/vt/collective/reduce/get_reduce_stamp.h
@@ -48,6 +48,7 @@
 #include "vt/collective/reduce/reduce_scope.h"
 #include "vt/messaging/message.h"
 
+#include <tuple>
 #include <utility>
 #include <type_traits>
 
diff --git a/src/vt/collective/reduce/reduce.h b/src/vt/collective/reduce/reduce.h
index be969eebd1..1293782edb 100644
--- a/src/vt/collective/reduce/reduce.h
+++ b/src/vt/collective/reduce/reduce.h
@@ -168,10 +168,19 @@ struct Reduce : virtual collective::tree::Tree {
     return reduce<MsgT, f>(root, msg, id, num_contrib);
   }
 
-  //////////////////////////////////////////////////////////////
-  //////////////////////////////////////////////////////////////
-  //////////////////////////////////////////////////////////////
-  template <template<typename Arg> class Op, auto f, typename... Params>
+  /**
+   * \brief Perform a reduction without a message
+   *
+   * \param[in] root the root node to target
+   * \param[in] params parameters to reduce
+   *
+   * \return a pending send
+   */
+  template <
+    auto f,
+    template <typename Arg> class Op = NoneOp,
+    typename... Params
+  >
   PendingSendType reduce(Node root, Params&&... params) {
     using Tuple = typename FuncTraits<decltype(f)>::TupleType;
     using OpT = Op<Tuple>;
@@ -179,20 +188,7 @@ struct Reduce : virtual collective::tree::Tree {
   }
 
   template <typename Op, auto f, typename... Params>
-  PendingSendType reduce(Node root, Params&&... params) {
-    using Tuple = typename FuncTraits<decltype(f)>::TupleType;
-    using MsgT = ReduceTMsg<Tuple>;
-
-    auto msg = vt::makeMessage<MsgT>(std::tuple{std::forward<Params>(params)...});
-    auto id = detail::ReduceStamp{};
-    auto han = auto_registry::makeAutoHandlerParam<decltype(f), f, MsgT>();
-    msg->root_handler_ = han;
-
-    return reduce<Op, operators::NoCombine, MsgT>(root.get(), msg.get(), id, 1);
-  }
-  //////////////////////////////////////////////////////////////
-  //////////////////////////////////////////////////////////////
-  //////////////////////////////////////////////////////////////
+  PendingSendType reduce(Node root, Params&&... params);
 
   /**
    * \brief Reduce a message up the tree
diff --git a/src/vt/collective/reduce/reduce.impl.h b/src/vt/collective/reduce/reduce.impl.h
index ccd37b57c4..a68df467b1 100644
--- a/src/vt/collective/reduce/reduce.impl.h
+++ b/src/vt/collective/reduce/reduce.impl.h
@@ -83,6 +83,20 @@ void Reduce::reduceRootRecv(MsgT* msg) {
     .run();
 }
 
+template <typename Op, auto f, typename... Params>
+Reduce::PendingSendType Reduce::reduce(Node root, Params&&... params) {
+  using Tuple = typename FuncTraits<decltype(f)>::TupleType;
+  using MsgT = ReduceTMsg<Tuple>;
+
+  auto msg = vt::makeMessage<MsgT>(std::forward<Params>(params)...);
+  auto id = detail::ReduceStamp{};
+  auto han = auto_registry::makeAutoHandlerParam<decltype(f), f, MsgT>();
+  msg->root_handler_ = han;
+
+  return reduce<Op, operators::NoCombine, MsgT>(root.get(), msg.get(), id, 1);
+}
+
+
 template <typename OpT, typename MsgT, ActiveTypedFnType<MsgT> *f>
 Reduce::PendingSendType Reduce::reduce(
   NodeType const& root, MsgT* msg, Callback<MsgT> cb, detail::ReduceStamp id,