From 753a6f849d73ce83114c90ea86d1ef4d7e98dbeb Mon Sep 17 00:00:00 2001
From: Maximilian Bergbauer <bergbauer@lnm.mw.tum.de>
Date: Mon, 7 Jun 2021 16:59:12 +0200
Subject: [PATCH] Add grid reordering to read_exodusii function

---
 source/grid/grid_in.cc                           | 15 +++++++++++++++
 ..._exodusii.with_trilinos_with_seacas=on.output | 16 ++++++++--------
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/source/grid/grid_in.cc b/source/grid/grid_in.cc
index 1edbd5263b..a49a6af20f 100644
--- a/source/grid/grid_in.cc
+++ b/source/grid/grid_in.cc
@@ -3251,6 +3251,8 @@ GridIn<dim, spacedim>::read_exodusii(
   ierr = ex_get_ids(ex_id, EX_ELEM_BLOCK, element_block_ids.data());
   AssertThrowExodusII(ierr);
 
+  bool is_only_quad_or_hex = true;
+
   std::vector<CellData<dim>> cells;
   // Elements are grouped together by same reference cell type in element
   // blocks. There may be multiple blocks for a single reference cell type,
@@ -3278,6 +3280,9 @@ GridIn<dim, spacedim>::read_exodusii(
       const ReferenceCell type =
         exodusii_name_to_type(string_temp.data(), n_nodes_per_element);
 
+      if (type.is_simplex())
+        is_only_quad_or_hex = false;
+
       // The number of nodes per element may be larger than what we want to
       // read - for example, if the Exodus file contains a QUAD9 element, we
       // only want to read the first four values and ignore the rest.
@@ -3312,6 +3317,16 @@ GridIn<dim, spacedim>::read_exodusii(
   ierr = ex_close(ex_id);
   AssertThrowExodusII(ierr);
 
+  if (is_only_quad_or_hex)
+    {
+      // do some clean-up on vertices...
+      GridTools::delete_unused_vertices(vertices, cells, pair.first);
+      // ... and cells
+      if (dim == spacedim)
+        GridTools::invert_all_negative_measure_cells(vertices, cells);
+      GridTools::consistently_order_cells(cells);
+    }
+
   tria->create_triangulation(vertices, cells, pair.first);
   ExodusIIData out;
   out.id_to_sideset_ids = std::move(pair.second);
diff --git a/tests/grid/grid_in_exodusii.with_trilinos_with_seacas=on.output b/tests/grid/grid_in_exodusii.with_trilinos_with_seacas=on.output
index 82867988ed..95fdbf3a5c 100644
--- a/tests/grid/grid_in_exodusii.with_trilinos_with_seacas=on.output
+++ b/tests/grid/grid_in_exodusii.with_trilinos_with_seacas=on.output
@@ -27,14 +27,14 @@ POINTS 8 double
 7.0 7.0 0
 
 CELLS 8 34
-4 0 1 2 3
-4 2 1 7 6
-4 4 6 7 5
-4 0 3 4 5
-4 3 2 6 4
-2 0 1
-2 0 5
-2 1 7
+4 2 3 0 1
+4 6 2 1 7
+4 6 7 5 4
+4 4 5 0 3
+4 6 4 3 2
+2 1 0
+2 5 0
+2 7 1
 
 CELL_TYPES 8
 9 9 9 9 9 
-- 
2.39.5