Added test for generic mpi4py-fft Laplacian class

Author: brownbaerchen

pySDC/tests/test_problems/test_generic_MPIFFT.py

@@ -0,0 +1,40 @@
+import pytest
+
+
+@pytest.mark.mpi4py
+@pytest.mark.parametrize('nx', [16, 32])
+@pytest.mark.parametrize('ny', [16, 32])
+@pytest.mark.parametrize('nz', [0])
+@pytest.mark.parametrize('f', [1, 3])
+@pytest.mark.parametrize('direction', [0, 1, 10])
+def test_derivative(nx, ny, nz, f, direction):
+    from pySDC.implementations.problem_classes.generic_MPIFFT_Laplacian import IMEX_Laplacian_MPIFFT
+
+    nvars = (nx, ny)
+    if nz > 0:
+        nvars.append(nz)
+    prob = IMEX_Laplacian_MPIFFT(nvars=nvars)
+
+    xp = prob.xp
+
+    if direction == 0:
+        u = xp.sin(f * prob.X[0])
+        du_expect = -(f**2) * xp.sin(f * prob.X[0])
+    elif direction == 1:
+        u = xp.sin(f * prob.X[1])
+        du_expect = -(f**2) * xp.sin(f * prob.X[1])
+    elif direction == 10:
+        u = xp.sin(f * prob.X[1]) + xp.cos(f * prob.X[0])
+        du_expect = -(f**2) * xp.sin(f * prob.X[1]) - f**2 * xp.cos(f * prob.X[0])
+    else:
+        raise
+
+    du = prob.eval_f(u, 0).impl
+    assert xp.allclose(du, du_expect), 'Got unexpected derivative'
+
+    _u = prob.solve_system(du, factor=1e8, u0=du, t=0) * -1e8
+    assert xp.allclose(_u, u, atol=1e-7), 'Got unexpected inverse derivative'
+
+
+if __name__ == '__main__':
+    test_derivative(32, 32, 0, 1, 1)