fix: wrong result with symmetries and direct solver (capytaine#594)

capytaine/bem/engines.py

@@ -123,10 +123,10 @@ def build_matrices(self, mesh1, mesh2, free_surface, water_depth, wavenumber, gr
 
             S_a, V_a = self.build_matrices(
                 mesh1[0], mesh2[0], free_surface, water_depth, wavenumber,
-                green_function)
+                green_function, adjoint_double_layer=adjoint_double_layer)
             S_b, V_b = self.build_matrices(
                 mesh1[0], mesh2[1], free_surface, water_depth, wavenumber,
-                green_function)
+                green_function, adjoint_double_layer=adjoint_double_layer)
 
             return BlockSymmetricToeplitzMatrix([[S_a, S_b]]), BlockSymmetricToeplitzMatrix([[V_a, V_b]])
 

docs/changelog.rst

@@ -33,6 +33,9 @@ Bug fixes
 
 * User does not need to import `pyplot` themself before running `show_matplotlib()` (:pull:`592`)
 
+* Fixes usage of ``ReflectionSymmetricMesh`` with direct solver (:issue:`593` and :pull:`594`).
+
+
 -------------------------------
 New in version 2.2 (2024-07-08)
 -------------------------------

pytest/test_bem_solver.py

@@ -48,6 +48,18 @@ def test_direct_solver(sphere):
     assert direct_result.forces["Surge"] == pytest.approx(indirect_result.forces["Surge"], rel=1e-1)
 
 
+@pytest.mark.parametrize("method", ["direct", "indirect"])
+def test_same_result_with_symmetries(method):
+    solver = cpt.BEMSolver()
+    sym_mesh = cpt.ReflectionSymmetricMesh(cpt.mesh_sphere(center=(0, 2, 0)).immersed_part(), cpt.xOz_Plane)
+    sym_body = cpt.FloatingBody(mesh=sym_mesh, dofs=cpt.rigid_body_dofs())
+    sym_result = solver.solve(cpt.DiffractionProblem(body=sym_body, omega=1.0), method=method)
+    mesh = sym_mesh.merged()
+    body = cpt.FloatingBody(mesh=mesh, dofs=cpt.rigid_body_dofs())
+    result = solver.solve(cpt.DiffractionProblem(body=body, omega=1.0), method=method)
+    assert sym_result.forces["Surge"] == pytest.approx(result.forces["Surge"], rel=1e-10)
+
+
 def test_parallelization(sphere):
     pytest.importorskip("joblib")
     solver = cpt.BEMSolver()