From f2cc0780897b772879c83b7346c1f4138c01d656 Mon Sep 17 00:00:00 2001
From: Sam Reeve <6740307+streeve@users.noreply.github.com>
Date: Fri, 19 Apr 2024 10:10:16 -0400
Subject: [PATCH] Create body term applied to all local particles (e.g.
 temperature)

---
 src/CabanaPD.hpp          |  1 +
 src/CabanaPD_BodyTerm.hpp | 53 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 src/CabanaPD_BodyTerm.hpp

diff --git a/src/CabanaPD.hpp b/src/CabanaPD.hpp
index 95e66b32..bd094231 100644
--- a/src/CabanaPD.hpp
+++ b/src/CabanaPD.hpp
@@ -12,6 +12,7 @@
 #ifndef CABANAPD_HPP
 #define CABANAPD_HPP
 
+#include <CabanaPD_BodyTerm.hpp>
 #include <CabanaPD_Boundary.hpp>
 #include <CabanaPD_Comm.hpp>
 #include <CabanaPD_Fields.hpp>
diff --git a/src/CabanaPD_BodyTerm.hpp b/src/CabanaPD_BodyTerm.hpp
new file mode 100644
index 00000000..b575ce44
--- /dev/null
+++ b/src/CabanaPD_BodyTerm.hpp
@@ -0,0 +1,53 @@
+/****************************************************************************
+ * Copyright (c) 2022-2023 by Oak Ridge National Laboratory                 *
+ * All rights reserved.                                                     *
+ *                                                                          *
+ * This file is part of CabanaPD. CabanaPD is distributed under a           *
+ * BSD 3-clause license. For the licensing terms see the LICENSE file in    *
+ * the top-level directory.                                                 *
+ *                                                                          *
+ * SPDX-License-Identifier: BSD-3-Clause                                    *
+ ****************************************************************************/
+
+#ifndef BODYTERM_H
+#define BODYTERM_H
+
+#include <Kokkos_Core.hpp>
+
+#include <Cabana_Core.hpp>
+
+namespace CabanaPD
+{
+
+template <class UserFunctor>
+struct BodyTerm
+{
+    UserFunctor _user_functor;
+
+    BodyTerm( UserFunctor user )
+        : _user_functor( user )
+    {
+    }
+
+    // This function interface purposely matches the boundary conditions in
+    // order to use the two interchangeably in Solvers.
+    template <class ExecSpace, class ParticleType>
+    void apply( ExecSpace, ParticleType& particles, const double time )
+    {
+        Kokkos::RangePolicy<ExecSpace> policy( 0, particles.n_local );
+        auto user = _user_functor;
+        Kokkos::parallel_for(
+            "CabanaPD::BodyTerm::apply", policy,
+            KOKKOS_LAMBDA( const int p ) { user( p, time ); } );
+    }
+};
+
+template <class UserFunctor>
+auto createBodyTerm( UserFunctor user_functor )
+{
+    return BodyTerm<UserFunctor>( user_functor );
+}
+
+} // namespace CabanaPD
+
+#endif