From cc7cf49a55ea32b7cfb96bc56986a349c356a946 Mon Sep 17 00:00:00 2001
From: "Vasco C. B. Ferreira" <vascocbf@gmail.com>
Date: Wed, 8 Jul 2026 11:11:35 +0200
Subject: [PATCH] update on poisson :: refine

---
 nufi/poisson_problem.h | 28 ++++++++++++++++++++--------
 src/nufi_solver.cc     |  1 -
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/nufi/poisson_problem.h b/nufi/poisson_problem.h
index 54755e7..475cd62 100644
--- a/nufi/poisson_problem.h
+++ b/nufi/poisson_problem.h
@@ -369,8 +369,14 @@ template <int dim> void PoissonProblem<dim>::assemble_system() {
   }
 }
 
-template <int dim> void PoissonProblem<dim>::coarse_and_refine_grid() {
+template <int dim>
+void PoissonProblem<dim>::coarse_and_refine_grid(
+    std::vector<Vector<double>> &solution_history) {
   // Add refinement and coasring algorithm here
+
+  //======//======//
+  // CHECK step-15.
+  //======//======//
   Vector<float> error_per_cell(triangulation.n_active_cells());
 
   KellyErrorEstimator<dim>::estimate(
@@ -384,15 +390,21 @@ template <int dim> void PoissonProblem<dim>::coarse_and_refine_grid() {
 
   triangulation.prepare_coarsening_and_refinement();
 
-  // solution tranafer
+  // old solutions transfer
+  const size_t N_sols = solution_history.size();
 
-  // setup_system
+  SolutionTransfer<dim, Vector<double>> transfer(dof_handler);
+  transfer.prepare_for_coarsening_and_refinement(solution_history);
 
-  // solution_transfer interpolate
-  // non_zero_constraint.distribute(current solution)
-  //
-  //======//======//
-  // CHECK step-15.
+  triangulation.execute_coarsening_and_refinement();
+
+  setup_system();
+
+  transfer.interpolate(solution_history);
+
+  solution = solution_history.back();
+
+  constraints.distribute(solution);
 
   // rebuild cells with the grid
   cell_locator.rebuild(dof_handler, triangulation);
diff --git a/src/nufi_solver.cc b/src/nufi_solver.cc
index d5aa1dc..75637eb 100644
--- a/src/nufi_solver.cc
+++ b/src/nufi_solver.cc
@@ -205,7 +205,6 @@ void NuFISolver::run() {
     });
 
     poisson.solve_step();
-
     phi_history.push_back(poisson.get_solution());
 
     // std::vector<double> sampled_potential =