Recalc cutoff on skin change

src/core/electrostatics_magnetostatics/coulomb.cpp

@@ -107,11 +107,11 @@ double cutoff(const Utils::Vector3d &box_l) {
   switch (coulomb.method) {
   case COULOMB_MMM1D:
     return std::numeric_limits<double>::infinity();
+  case COULOMB_MMM2D:
+    return std::numeric_limits<double>::min();
 #ifdef P3M
   case COULOMB_ELC_P3M:
     return std::max(elc_params.space_layer, p3m.params.r_cut_iL * box_l[0]);
-  case COULOMB_MMM2D:
-    return layer_h - skin;
   case COULOMB_P3M_GPU:
   case COULOMB_P3M:
     /* do not use precalculated r_cut here, might not be set yet */

testsuite/python/CMakeLists.txt

@@ -197,6 +197,7 @@ python_test(FILE time_series.py MAX_NUM_PROC 1)
 python_test(FILE linear_momentum.py)
 python_test(FILE linear_momentum_lb.py MAX_NUM_PROC 2 LABELS gpu)
 python_test(FILE mmm1d.py MAX_NUM_PROC 2 LABELS gpu)
+python_test(FILE mmm2d_setup.py MAX_NUM_PROC 2)
 
 if(PY_H5PY)
   python_test(FILE h5md.py MAX_NUM_PROC 2)

testsuite/python/mmm2d_setup.py

@@ -0,0 +1,51 @@
+# Copyright (C) 2010-2018 The ESPResSo project
+#
+# This file is part of ESPResSo.
+#
+# ESPResSo is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# ESPResSo is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+import unittest as ut
+import unittest_decorators as utx
+import espressomd
+import espressomd.electrostatics
+
+
+@utx.skipIfMissingFeatures(["ELECTROSTATICS"])
+class MMM2D_setup(ut.TestCase):
+    system = espressomd.System(box_l=[10.0, 10.0, 10.0])
+    system.time_step = 0.01
+
+    def test_nonzero_maxcut(self):
+
+        self.system.cell_system.set_layered(
+            n_layers=20, use_verlet_lists=False)
+
+        self.system.periodicity = [1, 1, 0]
+
+        self.system.part.add(pos=(1.0, 1.0, 1.0), q=1)
+        self.system.part.add(pos=(9.0, 9.0, 9.0), q=-1)
+
+        # No interaction so far: max_cut == 0
+        self.assertTrue(self.system.cell_system.get_state()["max_cut"] == 0)
+
+        mmm2d = espressomd.electrostatics.MMM2D(prefactor=1.0, maxPWerror=1e-3)
+        self.system.actors.add(mmm2d)
+
+        # MMM2D alters max_cut to small eps
+        self.assertTrue(self.system.cell_system.get_state()["max_cut"] != 0)
+
+        # Test integration
+        self.system.integrator.run(0)
+
+if __name__ == "__main__":
+    ut.main()