Add "gl" Lagrange variant (#295)

* legendre and legendre-polynomials

* gl and legendre

* changelog

* update tests

Author: mscroggs

CHANGELOG_SINCE_LAST_VERSION.md

@@ -0,0 +1 @@
+- Allow "gl" variant of Lagrange element

symfem/elements/lagrange.py

@@ -61,7 +61,10 @@ def __init__(self, reference: Reference, order: int, variant: str = "equispaced"
                     for f in basis:
                         dofs.append(IntegralAgainst(reference, f, (edim, e_n)))
         else:
-            points, _ = get_quadrature(variant, order + 1)
+            if variant == "gl":
+                points, _ = get_quadrature("legendre", order + 1)
+            else:
+                points, _ = get_quadrature(variant, order + 1)
             if variant != "equispaced":
                 assert reference.name in ["interval", "quadrilateral", "hexahedron"]
 

symfem/elements/lagrange_prism.py

@@ -54,7 +54,10 @@ def __init__(self, reference: Reference, order: int, variant: str = "equispaced"
         elif variant == "lobatto":
             raise NotImplementedError()
         else:
-            points, _ = get_quadrature(variant, order + 1)
+            if variant == "gl":
+                points, _ = get_quadrature("legendre", order + 1)
+            else:
+                points, _ = get_quadrature(variant, order + 1)
 
             # Vertices
             for v_n, v in enumerate(reference.vertices):

symfem/elements/lagrange_pyramid.py

@@ -49,7 +49,10 @@ def __init__(self, reference: Reference, order: int, variant: str = "equispaced"
         elif variant == "lobatto":
             raise NotImplementedError()
         else:
-            points, _ = get_quadrature(variant, order + 1)
+            if variant == "gl":
+                points, _ = get_quadrature("legendre", order + 1)
+            else:
+                points, _ = get_quadrature(variant, order + 1)
 
             # Vertices
             for v_n, v in enumerate(reference.vertices):

test/utils.py

@@ -9,12 +9,14 @@
         "P": [
             ({"variant": "equispaced"}, range(6)),
             ({"variant": "lobatto"}, range(4)),
+            ({"variant": "gl"}, [0, 1]),
             ({"variant": "legendre"}, range(5)),
         ],
         "vP": [
             ({"variant": "equispaced"}, range(6)),
             ({"variant": "lobatto"}, range(3)),
             ({"variant": "radau"}, range(3)),
+            ({"variant": "gl"}, [0, 1]),
             ({"variant": "legendre"}, range(3)),
         ],
         "dPc": [({"variant": "equispaced"}, range(6)), ({"variant": "lobatto"}, range(4))],