From 26fafd319e8bc5a94952fffed20e95b661c6b2e0 Mon Sep 17 00:00:00 2001
From: Patrick Shriwise <pshriwise@gmail.com>
Date: Thu, 5 Dec 2019 22:29:47 -0600
Subject: [PATCH] Start of libmesh implementation.

---
 CMakeLists.txt | 16 ++++++++++++++++
 src/mesh.cpp   | 31 +++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 499e006a01..d104405424 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -73,6 +73,16 @@ if(libmesh)
   find_package(LIBMESH REQUIRED)
 endif()
 
+#===============================================================================
+# libmesh Unstructured Mesh Support
+#===============================================================================
+if(libmesh)
+  find_package(LIBMESH REQUIRED)
+  set(LIBMESH_LIBRARIES mesh_opt)
+  set(LIBMESH_INCLUDE_DIRS "${LIBMESH}/../include/")
+  link_directories(${LIBMESH})
+endif()
+
 #===============================================================================
 # HDF5 for binary output
 #===============================================================================
@@ -418,6 +428,12 @@ if(libmesh)
   target_link_libraries(libopenmc PkgConfig::LIBMESH)
 endif()
 
+if(libmesh)
+  target_compile_definitions(libopenmc PRIVATE LIBMESH)
+  target_link_libraries(libopenmc ${LIBMESH_LIBRARIES})
+  target_include_directories(libopenmc PRIVATE ${LIBMESH_INCLUDE_DIRS})
+endif()
+
 #===============================================================================
 # openmc executable
 #===============================================================================
diff --git a/src/mesh.cpp b/src/mesh.cpp
index 1fc5169c52..47f9a1d611 100644
--- a/src/mesh.cpp
+++ b/src/mesh.cpp
@@ -2372,6 +2372,37 @@ double LibMesh::volume(int bin) const { return m_->elem_ref(bin).volume(); }
 
 #endif // LIBMESH
 
+UnstructuredMeshBase::UnstructuredMeshBase(pugi::xml_node node) : Mesh(node) {
+    // check the mesh type
+  if (check_for_node(node, "type")) {
+    auto temp = get_node_value(node, "type", true, true);
+    if (temp != "unstructured") {
+      fatal_error("Invalid mesh type: " + temp);
+    }
+  }
+
+  // get the filename of the unstructured mesh to load
+  if (check_for_node(node, "mesh_file")) {
+    filename_ = get_node_value(node, "mesh_file");
+  }
+  else {
+    fatal_error("No filename supplied for unstructured mesh with ID: " +
+                std::to_string(id_));
+  }
+}
+
+#ifdef LIBMESH
+LibMesh::LibMesh(pugi::xml_node node) : UnstructuredMeshBase(node) {
+  libMesh::LibMeshInit init(0, NULL);
+
+  m_ = std::unique_ptr<libMesh::Mesh>(new libMesh::Mesh(init.comm(), 3));
+  m_->read(filename_);
+
+  point_locator_ = m_->sub_point_locator();
+  m_->find_neighbors();
+}
+#endif
+
 //==============================================================================
 // Non-member functions
 //==============================================================================