Merge #3331

3331: Testcase for ELC and MMM2D r=fweik a=reinaual

Analytical testcase for ELC and MMM2D

Co-authored-by: Alexander Reinauer <st144434@stud.uni-stuttgart.de>

testsuite/python/CMakeLists.txt

@@ -191,6 +191,7 @@ 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 elc.py MAX_NUM_PROC 2)
+python_test(FILE elc_and_mmm2d_vs_analytic.py MAX_NUM_PROC 2)
 
 if(PY_H5PY)
   python_test(FILE h5md.py MAX_NUM_PROC 2)

testsuite/python/elc_and_mmm2d_vs_analytic.py

@@ -0,0 +1,124 @@
+# Copyright (C) 2019 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 numpy as np
+import espressomd.electrostatics
+from espressomd import electrostatic_extensions
+
+
+@utx.skipIfMissingFeatures(["P3M"])
+class ELC_and_MMM2D_vs_analytic(ut.TestCase):
+    # Handle to espresso system
+    box_l = 200.
+    system = espressomd.System(box_l=[box_l, box_l, box_l])
+    accuracy = 1e-7
+    check_accuracy = 1e-4
+    elc_gap = 75.0
+    system.time_step = 0.01
+    delta_mid_top = 1.
+    delta_mid_bot = 39. / 41.
+    distance = 1.
+
+    number_samples = 25
+    zPos = np.linspace(0.1, 8, number_samples)
+    q = np.arange(-5.0, 5.1, 2.5)
+
+    def test_elc_and_mmm2d(self):
+        """
+        Testing ELC and MMM2D against the analytic solution for an infinite large simulation box with dielectric contrast on the bottom of the box, which can be calculated analytically with image charges.
+        """
+        # MMM2D
+        self.system.cell_system.skin = 0.1
+        buf_node_grid = self.system.cell_system.node_grid
+        self.system.cell_system.set_layered(
+            n_layers=10, use_verlet_lists=False)
+
+        self.system.periodicity = [1, 1, 0]
+
+        self.system.part.add(id=1, pos=self.system.box_l / 2., q=self.q[0])
+        self.system.part.add(id=2, pos=self.system.box_l / 2. + [0, 0, 1],
+                             q=-self.q[0])
+
+        # MMM2D
+        mmm2d = espressomd.electrostatics.MMM2D(prefactor=1.0,
+                                                maxPWerror=self.accuracy,
+                                                delta_mid_bot=self.delta_mid_bot,
+                                                delta_mid_top=self.delta_mid_top,
+                                                dielectric_contrast_on=1)
+
+        self.system.actors.add(mmm2d)
+
+        mmm2d_results = self.scan()
+
+        self.system.actors.remove(mmm2d)
+
+        # ELC
+        self.system.box_l = [self.box_l, self.box_l, self.box_l + self.elc_gap]
+        self.system.cell_system.set_domain_decomposition(
+            use_verlet_lists=True)
+        self.system.cell_system.node_grid = buf_node_grid
+        self.system.periodicity = [1, 1, 1]
+        p3m = espressomd.electrostatics.P3M(prefactor=1.,
+                                            accuracy=self.accuracy,
+                                            mesh=[58, 58, 70],
+                                            cao=4)
+        self.system.actors.add(p3m)
+
+        elc = electrostatic_extensions.ELC(gap_size=self.elc_gap,
+                                           maxPWerror=self.accuracy,
+                                           delta_mid_bot=self.delta_mid_bot,
+                                           delta_mid_top=self.delta_mid_top)
+        self.system.actors.add(elc)
+
+        elc_results = self.scan()
+
+        # ANALYTIC SOLUTION
+        charge_reshaped = np.square(self.q.reshape(-1, 1))
+        analytic_force = charge_reshaped * (1 / self.distance ** 2 + self.delta_mid_bot * (
+            1 / np.square(2 * self.zPos) - 1 / np.square(2 * self.zPos + self.distance)))
+        analytic_energy = charge_reshaped * (-1 / self.distance + self.delta_mid_bot * (1 / (
+            4 * self.zPos) - 1 / (2 * self.zPos + self.distance) + 1 / (4 * (self.zPos + self.distance))))
+
+        analytic_results = np.dstack((analytic_force, analytic_energy))
+
+        self.assertTrue(np.testing.assert_allclose(
+            mmm2d_results, analytic_results, rtol=0, atol=self.check_accuracy) is None)
+
+        self.assertTrue(np.testing.assert_allclose(
+            elc_results, analytic_results, rtol=0, atol=self.check_accuracy) is None)
+
+    def scan(self):
+        result_array = np.empty((len(self.q), len(self.zPos), 2))
+        for chargeIndex, charge in enumerate(self.q):
+            self.system.part[1].q = charge
+            self.system.part[2].q = -charge
+            for i, z in enumerate(self.zPos):
+                pos = self.system.part[1].pos
+                self.system.part[1].pos = [pos[0], pos[1], z]
+                self.system.part[2].pos = [pos[0], pos[1], z + self.distance]
+
+                self.system.integrator.run(0)
+                result_array[chargeIndex, i, 0] = self.system.part[1].f[2]
+                result_array[chargeIndex, i, 1] = self.system.analysis.energy()[
+                    "total"]
+        return result_array
+
+
+if __name__ == "__main__":
+    ut.main()