add symmetric to finite element (#684)

Author: mscroggs

ffcx/codegeneration/C/finite_element.py

@@ -41,6 +41,7 @@ def generator(ir, options):
     d["num_sub_elements"] = ir.num_sub_elements
     d["block_size"] = ir.block_size
     d["discontinuous"] = "true" if ir.discontinuous else "false"
+    d["symmetric"] = "true" if ir.symmetric else "false"
 
     if ir.lagrange_variant is None:
         d["lagrange_variant"] = -1

ffcx/codegeneration/C/finite_element_template.py

@@ -27,6 +27,7 @@
   .reference_value_shape = {reference_value_shape},
   .reference_value_size = {reference_value_size},
   .degree = {degree},
+  .symmetric = {symmetric},
   .block_size = {block_size},
   .basix_family = {basix_family},
   .basix_cell = {basix_cell},

ffcx/codegeneration/ufcx.h

@@ -107,6 +107,9 @@ extern "C"
     /// Maximum polynomial degree of the finite element function space
     int degree;
 
+    /// Is the value a symmetric 2-tensor
+    bool symmetric;
+
     /// Block size for a VectorElement. For a TensorElement, this is the
     /// product of the tensor's dimensions
     int block_size;

ffcx/ir/representation.py

@@ -97,6 +97,7 @@ class ElementIR(typing.NamedTuple):
     space_dimension: int
     reference_value_shape: tuple[int, ...]
     degree: int
+    symmetric: bool
     num_sub_elements: int
     block_size: int
     sub_elements: list[str]
@@ -296,6 +297,9 @@ def _compute_element_ir(element, element_numbers, finite_element_names):
     ir["basix_cell"] = element.cell_type
     ir["discontinuous"] = element.discontinuous
     ir["degree"] = element.degree
+    ir["symmetric"] = isinstance(element, basix.ufl._BlockedElement) and isinstance(
+        element._pullback, ufl.pullback.SymmetricPullback
+    )
     ir["reference_value_shape"] = element.reference_value_shape
 
     ir["num_sub_elements"] = element.num_sub_elements