From ecd2ed13f883efffdbde4b49aab8e71ff389fbdd Mon Sep 17 00:00:00 2001
From: Jane Tournois <jane.tournois@geometryfactory.com>
Date: Thu, 19 Jun 2025 15:01:45 +0200
Subject: [PATCH] add a test for determinism of Tetrahedral_remeshing

---
 .../test/Tetrahedral_remeshing/CMakeLists.txt |   1 +
 ...test_tetrahedral_remeshing_determinism.cpp | 102 ++++++++++++++++++
 2 files changed, 103 insertions(+)
 create mode 100644 Tetrahedral_remeshing/test/Tetrahedral_remeshing/test_tetrahedral_remeshing_determinism.cpp

diff --git a/Tetrahedral_remeshing/test/Tetrahedral_remeshing/CMakeLists.txt b/Tetrahedral_remeshing/test/Tetrahedral_remeshing/CMakeLists.txt
index 63bc0c06023..3747ae19125 100644
--- a/Tetrahedral_remeshing/test/Tetrahedral_remeshing/CMakeLists.txt
+++ b/Tetrahedral_remeshing/test/Tetrahedral_remeshing/CMakeLists.txt
@@ -16,6 +16,7 @@ create_single_source_cgal_program("test_tetrahedral_remeshing_with_features.cpp"
 create_single_source_cgal_program("test_tetrahedral_remeshing_of_one_subdomain.cpp")
 create_single_source_cgal_program("test_tetrahedral_remeshing_io.cpp")
 create_single_source_cgal_program("test_tetrahedral_remeshing_from_mesh_file.cpp")
+create_single_source_cgal_program("test_tetrahedral_remeshing_determinism.cpp")
 
 # Test MLS projection
 add_executable(test_tetrahedral_remeshing_mls
diff --git a/Tetrahedral_remeshing/test/Tetrahedral_remeshing/test_tetrahedral_remeshing_determinism.cpp b/Tetrahedral_remeshing/test/Tetrahedral_remeshing/test_tetrahedral_remeshing_determinism.cpp
new file mode 100644
index 00000000000..024b1f325d5
--- /dev/null
+++ b/Tetrahedral_remeshing/test/Tetrahedral_remeshing/test_tetrahedral_remeshing_determinism.cpp
@@ -0,0 +1,102 @@
+//#define CGAL_TETRAHEDRAL_REMESHING_VERBOSE
+//#define CGAL_TETRAHEDRAL_REMESHING_DEBUG
+//#define CGAL_TETRAHEDRAL_REMESHING_GENERATE_INPUT_FILES
+
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+
+#include <CGAL/Tetrahedral_remeshing/Remeshing_triangulation_3.h>
+#include <CGAL/tetrahedral_remeshing.h>
+#include <CGAL/Tetrahedral_remeshing/tetrahedral_remeshing_io.h>
+#include <CGAL/Random.h>
+
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <vector>
+#include <cassert>
+
+typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
+
+typedef CGAL::Tetrahedral_remeshing::Remeshing_triangulation_3<K> Remeshing_triangulation;
+
+template<typename T3>
+void generate_input_one_subdomain(const std::size_t nbv, T3& tr)
+{
+  CGAL::Random rng;
+
+  typedef typename T3::Point Point;
+  std::vector<Point> pts;
+  while (pts.size() < nbv)
+  {
+    const float x = rng.uniform_real(-10.f, 10.f);
+    const float y = rng.uniform_real(-10.f, 10.f);
+    const float z = rng.uniform_real(-10.f, 10.f);
+
+    pts.push_back(Point(x, y, z));
+  }
+  tr.insert(pts.begin(), pts.end());
+
+  for (typename T3::Cell_handle c : tr.finite_cell_handles())
+    c->set_subdomain_index(1);
+
+  assert(tr.is_valid(true));
+
+#ifdef CGAL_TETRAHEDRAL_REMESHING_GENERATE_INPUT_FILES
+  std::ofstream out("data/triangulation_one_subdomain.binary.cgal",
+                    std::ios_base::out | std::ios_base::binary);
+  CGAL::save_binary_triangulation(out, tr);
+  out.close();
+#endif
+}
+
+int main(int argc, char* argv[])
+{
+  std::cout << "CGAL Random seed = " << CGAL::get_default_random().get_seed() << std::endl;
+
+  // Collect options
+  std::size_t nb_runs = 5;
+
+  Remeshing_triangulation tr;
+  generate_input_one_subdomain(1000, tr);
+
+  const int target_edge_length = (argc > 1) ? atoi(argv[1]) : 1;
+
+  std::ofstream ofs0("in.mesh");
+  CGAL::IO::write_MEDIT(ofs0, tr);
+  ofs0.close();
+
+  Remeshing_triangulation tr_ref = tr; // Keep a reference for comparison
+
+  std::vector<std::string> output_tr;
+  output_tr.reserve(nb_runs);
+
+  for(std::size_t i = 0; i < nb_runs; ++i)
+  {
+    std::cout << "Run " << i << " of " << nb_runs << std::endl;
+
+    tr = tr_ref; // Reset triangulation to reference
+    CGAL::tetrahedral_isotropic_remeshing(tr, target_edge_length);
+
+    std::ostringstream oss;
+    CGAL::IO::write_MEDIT(oss, tr);
+    output_tr.push_back(oss.str());
+    oss.clear();
+
+    if(i == 0)
+      continue; // skip first run, it is the reference
+    else
+    {
+      if(0 != output_tr[i-1].compare(output_tr[i]))
+      {
+        std::cerr << "Run " << i << " differs from run " << i-1 << std::endl;
+        assert(false); // This should not happen
+      }
+      else
+      {
+        std::cout << "Run " << i << " is identical to run " << i-1 << std::endl;
+      }
+    }
+  }
+
+  return EXIT_SUCCESS;
+}