Update Laplace class and add unit tests (#645)

pina/problem/zoo/allen_cahn.py

@@ -2,32 +2,18 @@
 
 import torch
 from ... import Condition
-from ...equation import Equation
-from ...domain import CartesianDomain
-from ...operator import grad, laplacian
 from ...problem import SpatialProblem, TimeDependentProblem
-
-
-def allen_cahn_equation(input_, output_):
-    """
-    Implementation of the Allen Cahn equation.
-
-    :param LabelTensor input_: Input data of the problem.
-    :param LabelTensor output_: Output data of the problem.
-    :return: The residual of the Allen Cahn equation.
-    :rtype: LabelTensor
-    """
-    u_t = grad(output_, input_, components=["u"], d=["t"])
-    u_xx = laplacian(output_, input_, components=["u"], d=["x"])
-    return u_t - 0.0001 * u_xx + 5 * output_**3 - 5 * output_
+from ...equation import Equation, AllenCahn
+from ...utils import check_consistency
+from ...domain import CartesianDomain
 
 
 def initial_condition(input_, output_):
     """
     Definition of the initial condition of the Allen Cahn problem.
 
-    :param LabelTensor input_: Input data of the problem.
-    :param LabelTensor output_: Output data of the problem.
+    :param LabelTensor input_: The input data of the problem.
+    :param LabelTensor output_: The output data of the problem.
     :return: The residual of the initial condition.
     :rtype: LabelTensor
     """
@@ -64,6 +50,25 @@ class AllenCahnProblem(TimeDependentProblem, SpatialProblem):
     }
 
     conditions = {
-        "D": Condition(domain="D", equation=Equation(allen_cahn_equation)),
         "t0": Condition(domain="t0", equation=Equation(initial_condition)),
     }
+
+    def __init__(self, alpha=1e-4, beta=5):
+        """
+        Initialization of the :class:`AllenCahnProblem`.
+
+        :param alpha: The diffusion coefficient.
+        :type alpha: float | int
+        :param beta: The reaction coefficient.
+        :type beta: float | int
+        """
+        super().__init__()
+        check_consistency(alpha, (float, int))
+        check_consistency(beta, (float, int))
+        self.alpha = alpha
+        self.beta = beta
+
+        self.conditions["D"] = Condition(
+            domain="D",
+            equation=AllenCahn(alpha=self.alpha, beta=self.beta),
+        )