From 12b6deaacfe34bba5a56cf332decbe0b2b47ad0a Mon Sep 17 00:00:00 2001
From: Gavin Ridley <gavin.keith.ridley@gmail.com>
Date: Thu, 11 Feb 2021 16:43:34 -0500
Subject: [PATCH] remove unnecessary pass by value for plot class

---
 include/openmc/plot.h |  8 ++++----
 src/plot.cpp          | 15 +++++++--------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/include/openmc/plot.h b/include/openmc/plot.h
index 28c395bca..a15bc7e38 100644
--- a/include/openmc/plot.h
+++ b/include/openmc/plot.h
@@ -241,12 +241,12 @@ public:
 //! Add mesh lines to image data of a plot object
 //! \param[in] plot object
 //! \param[out] image data associated with the plot object
-void draw_mesh_lines(Plot pl, ImageData& data);
+void draw_mesh_lines(Plot const& pl, ImageData& data);
 
 //! Write a ppm image to file using a plot object's image data
 //! \param[in] plot object
 //! \param[out] image data associated with the plot object
-void output_ppm(Plot pl, const ImageData& data);
+void output_ppm(Plot const& pl, const ImageData& data);
 
 //! Initialize a voxel file
 //! \param[in] id of an open hdf5 file
@@ -280,11 +280,11 @@ void read_plots_xml();
 
 //! Create a ppm image for a plot object
 //! \param[in] plot object
-void create_ppm(Plot pl);
+void create_ppm(Plot const& pl);
 
 //! Create an hdf5 voxel file for a plot object
 //! \param[in] plot object
-void create_voxel(Plot pl);
+void create_voxel(Plot const& pl);
 
 //! Create a randomly generated RGB color
 //! \return RGBColor with random value
diff --git a/src/plot.cpp b/src/plot.cpp
index 20c3c986e..c7739c2c6 100644
--- a/src/plot.cpp
+++ b/src/plot.cpp
@@ -100,7 +100,7 @@ uint64_t plotter_seed = 1;
 extern "C"
 int openmc_plot_geometry()
 {
-  for (auto pl : model::plots) {
+  for (auto& pl : model::plots) {
     write_message(5, "Processing plot {}: {}...", pl.id_, pl.path_plot_);
 
     if (PlotType::slice == pl.type_) {
@@ -131,9 +131,8 @@ void read_plots_xml()
 
   pugi::xml_node root = doc.document_element();
   for (auto node : root.children("plot")) {
-    Plot pl(node);
-    model::plots.push_back(pl);
-    model::plot_map[pl.id_] = model::plots.size() - 1;
+    model::plots.emplace_back(node);
+    model::plot_map[model::plots.back().id_] = model::plots.size() - 1;
   }
 }
 
@@ -142,7 +141,7 @@ void read_plots_xml()
 // specification in the portable pixmap format (PPM)
 //==============================================================================
 
-void create_ppm(Plot pl)
+void create_ppm(Plot const& pl)
 {
 
   size_t width = pl.pixels_[0];
@@ -639,7 +638,7 @@ Plot::Plot(pugi::xml_node plot_node)
 // OUTPUT_PPM writes out a previously generated image to a PPM file
 //==============================================================================
 
-void output_ppm(Plot pl, const ImageData& data)
+void output_ppm(Plot const& pl, const ImageData& data)
 {
   // Open PPM file for writing
   std::string fname = pl.path_plot_;
@@ -669,7 +668,7 @@ void output_ppm(Plot pl, const ImageData& data)
 // DRAW_MESH_LINES draws mesh line boundaries on an image
 //==============================================================================
 
-void draw_mesh_lines(Plot pl, ImageData& data)
+void draw_mesh_lines(Plot const& pl, ImageData& data)
 {
   RGBColor rgb;
   rgb = pl.meshlines_color_;
@@ -776,7 +775,7 @@ void draw_mesh_lines(Plot pl, ImageData& data)
 // approximately 15MB.
 // =============================================================================
 
-void create_voxel(Plot pl)
+void create_voxel(Plot const& pl)
 {
   // compute voxel widths in each direction
   std::array<double, 3> vox;