fixup: use pi constant

src/CabanaPD.hpp

@@ -15,6 +15,7 @@
 #include <CabanaPD_BodyTerm.hpp>
 #include <CabanaPD_Boundary.hpp>
 #include <CabanaPD_Comm.hpp>
+#include <CabanaPD_Constants.hpp>
 #include <CabanaPD_DisplacementProfile.hpp>
 #include <CabanaPD_Fields.hpp>
 #include <CabanaPD_Force.hpp>

src/CabanaPD_Constants.hpp

@@ -0,0 +1,24 @@
+/****************************************************************************
+ * Copyright (c) 2022 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 CONSTANTS_H
+#define CONSTANTS_H
+
+#include "mpi.h"
+
+namespace CabanaPD
+{
+
+// FIXME: Kokkos::numbers::pi_v<double> when minimum 4.0 is required.
+constexpr double pi = M_PI;
+
+} // namespace CabanaPD
+#endif

src/CabanaPD_Input.hpp

@@ -18,6 +18,7 @@
 
 #include <nlohmann/json.hpp>
 
+#include <CabanaPD_Constants.hpp>
 #include <CabanaPD_Output.hpp>
 
 namespace CabanaPD
@@ -125,8 +126,7 @@ class Inputs
         double K = inputs["bulk_modulus"]["value"];
         double delta = inputs["horizon"]["value"];
         // FIXME: this is copied from the forces
-        double c =
-            18.0 * K / ( 3.141592653589793 * delta * delta * delta * delta );
+        double c = 18.0 * K / ( pi * delta * delta * delta * delta );
 
         for ( int i = -( m + 1 ); i < m + 2; i++ )
         {

src/force/CabanaPD_ForceModels_PMB.hpp

@@ -12,6 +12,7 @@
 #ifndef FORCE_MODELS_PMB_H
 #define FORCE_MODELS_PMB_H
 
+#include <CabanaPD_Constants.hpp>
 #include <CabanaPD_ForceModels.hpp>
 #include <CabanaPD_Types.hpp>
 
@@ -48,7 +49,7 @@ struct ForceModel<PMB, Elastic, TemperatureIndependent> : public BaseForceModel
     {
         delta = _delta;
         K = _K;
-        c = 18.0 * K / ( 3.141592653589793 * delta * delta * delta * delta );
+        c = 18.0 * K / ( pi * delta * delta * delta * delta );
     }
 };