From 254818cf7097789a8d0892e0f4724f8208da9f21 Mon Sep 17 00:00:00 2001
From: Pierre Alliez <pierre.alliez@inria.fr>
Date: Fri, 5 Jan 2024 14:39:47 +0100
Subject: [PATCH] added example that compares parallel with sequential MC

---
 .../examples/Isosurfacing_3/CMakeLists.txt    |  1 +
 .../marching_cubes_seq_vs_parallel.cpp        | 60 +++++++++++++++++++
 2 files changed, 61 insertions(+)
 create mode 100644 Isosurfacing_3/examples/Isosurfacing_3/marching_cubes_seq_vs_parallel.cpp

diff --git a/Isosurfacing_3/examples/Isosurfacing_3/CMakeLists.txt b/Isosurfacing_3/examples/Isosurfacing_3/CMakeLists.txt
index d32bd8a1962..85206736e94 100644
--- a/Isosurfacing_3/examples/Isosurfacing_3/CMakeLists.txt
+++ b/Isosurfacing_3/examples/Isosurfacing_3/CMakeLists.txt
@@ -7,6 +7,7 @@ project( Isosurfacing_3_Examples )
 find_package(CGAL REQUIRED)
 
 create_single_source_cgal_program( "marching_cubes_implicit_sphere.cpp" )
+create_single_source_cgal_program( "marching_cubes_seq_vs_parallel.cpp" )
 create_single_source_cgal_program( "marching_cubes_Cartesian_grid_sphere.cpp" )
 create_single_source_cgal_program( "marching_cubes_signed_mesh_offset.cpp" )
 create_single_source_cgal_program( "marching_cubes_multiple_mesh_offsets.cpp" )
diff --git a/Isosurfacing_3/examples/Isosurfacing_3/marching_cubes_seq_vs_parallel.cpp b/Isosurfacing_3/examples/Isosurfacing_3/marching_cubes_seq_vs_parallel.cpp
new file mode 100644
index 00000000000..a2150cb808d
--- /dev/null
+++ b/Isosurfacing_3/examples/Isosurfacing_3/marching_cubes_seq_vs_parallel.cpp
@@ -0,0 +1,60 @@
+#include <CGAL/Simple_cartesian.h>
+#include <CGAL/Isosurfacing_3/Implicit_Cartesian_grid_domain_3.h>
+#include <CGAL/Isosurfacing_3/marching_cubes_3.h>
+#include <CGAL/Bbox_3.h>
+#include <CGAL/boost/graph/IO/OFF.h>
+#include <CGAL/Timer.h>
+#include <vector>
+
+using Kernel = CGAL::Simple_cartesian<double>;
+using FT = typename Kernel::FT;
+using Point = typename Kernel::Point_3;
+using Vector = typename Kernel::Vector_3;
+using Point_range = std::vector<Point>;
+using Triangle_range = std::vector<std::vector<std::size_t> >;
+
+// Sphere function = Euclidean distance function to the origin
+auto sphere_function = [&](const Point& p) -> FT
+{
+	return std::sqrt(p.x() * p.x() + p.y() * p.y() + p.z() * p.z());
+};
+
+int main(int, char**)
+{
+  // box domain and spacing vector
+  const CGAL::Bbox_3 bbox{ -1.0, -1.0, -1.0,  1.0, 1.0, 1.0 };
+  const FT spacing = 0.01;
+  const Vector vec_spacing(spacing, spacing, spacing);
+
+  // create domain with sphere function
+  auto domain = CGAL::Isosurfacing::create_implicit_Cartesian_grid_domain<Kernel>
+	  (bbox, vec_spacing, sphere_function);
+
+  // points and triangles for the output indexed mesh
+  Point_range points;
+  Triangle_range triangles;
+
+  // run marching cubes sequential
+  std::cout << "marching cubes sequential...";
+  const FT isovalue = 0.8;
+  CGAL::Timer timer;
+  timer.start();
+  CGAL::Isosurfacing::marching_cubes<CGAL::Sequential_tag>(domain, isovalue, points, triangles);
+  timer.stop();
+  std::cout << "done (" << timer.time() << "s, " << triangles.size() << " triangles)" << std::endl;
+  CGAL::IO::write_OFF("output-seq.off", points, triangles);
+
+  // clear points and triangles
+  points.clear();
+  triangles.clear();
+
+  // run marching cubes parallel
+  std::cout << "marching cubes parallel...";
+  timer.start();
+  CGAL::Isosurfacing::marching_cubes<CGAL::Parallel_tag>(domain, isovalue, points, triangles);
+  timer.stop();
+  std::cout << "done (" << timer.time() << "s, " << triangles.size() << " triangles)" << std::endl;
+  CGAL::IO::write_OFF("output-parallel.off", points, triangles);
+
+  return EXIT_SUCCESS;
+}