support built-in equations in system

Author: GiovanniCanali

pina/equation/system_equation.py

@@ -32,9 +32,10 @@ def __init__(self, list_equation, reduction=None):
         check_consistency([list_equation], list)
 
         # equations definition
-        self.equations = []
-        for _, equation in enumerate(list_equation):
-            self.equations.append(Equation(equation))
+        self.equations = [
+            equation if isinstance(equation, Equation) else Equation(equation)
+            for equation in list_equation
+        ]
 
         # possible reduction
         if reduction == "mean":

tests/test_equations/test_system_equation.py

@@ -1,4 +1,4 @@
-from pina.equation import SystemEquation
+from pina.equation import SystemEquation, FixedValue, FixedGradient
 from pina.operator import grad, laplacian
 from pina import LabelTensor
 import torch
@@ -25,10 +25,20 @@ def foo():
 
 
 def test_constructor():
+
     SystemEquation([eq1, eq2])
     SystemEquation([eq1, eq2], reduction="sum")
+    SystemEquation(
+        [
+            FixedValue(value=0.0, components=["u1"]),
+            FixedGradient(value=0.0, components=["u2"]),
+        ],
+        reduction="mean",
+    )
+
     with pytest.raises(NotImplementedError):
         SystemEquation([eq1, eq2], reduction="foo")
+
     with pytest.raises(ValueError):
         SystemEquation(foo)
 
@@ -55,3 +65,13 @@ def test_residual():
     eq_1 = SystemEquation([eq1, eq2])
     res = eq_1.residual(pts, u)
     assert res.shape == torch.Size([10, 3])
+
+    system_eq = SystemEquation(
+        [
+            FixedValue(value=0.0, components=["u1"]),
+            FixedGradient(value=0.0, components=["u2"]),
+        ],
+        reduction="mean",
+    )
+    res = system_eq.residual(pts, u)
+    assert res.shape == torch.Size([10])