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ufl/algorithms/apply_restrictions.py

@@ -11,6 +11,7 @@
 # SPDX-License-Identifier:    LGPL-3.0-or-later
 
 from collections import defaultdict
+import numpy
 
 from ufl.algorithms.map_integrands import map_integrand_dags
 from ufl.classes import Restricted
@@ -21,6 +22,10 @@
 from ufl.sobolevspace import H1
 from ufl.geometry import GeometricQuantity
 from ufl.classes import Form, ReferenceGrad, ReferenceValue, Restricted, Indexed, MultiIndex, Index, FixedIndex, ComponentTensor, ListTensor, Zero
+from ufl.coefficient import Coefficient
+from ufl import indices
+from ufl.checks import is_cellwise_constant
+from ufl.tensors import as_tensor
 
 
 class RestrictionPropagator(MultiFunction):
@@ -357,3 +362,198 @@ def make_domain_integral_type_map(domain_restriction_map, integration_domain, in
     else:
         domain_integral_type_dict[integration_domain] = integration_type
     return domain_integral_type_dict
+
+
+# apply_coefficient_split
+
+
+class CoefficientSplitter(MultiFunction):
+
+    def __init__(self, coefficient_split):
+        MultiFunction.__init__(self)
+        self._coefficient_split = coefficient_split
+
+    expr = MultiFunction.reuse_if_untouched
+
+    def modified_terminal(self, o):
+        restriction = None
+        local_derivatives = 0
+        reference_value = False
+        t = o
+        while not t._ufl_is_terminal_:
+            print("")
+            print(repr(t))
+            assert t._ufl_is_terminal_modifier_, f"Got {repr(t)}"
+            if isinstance(t, ReferenceValue):
+                assert not reference_value, "Got twice pulled back terminal!"
+                reference_value = True
+                t, = t.ufl_operands
+            elif isinstance(t, ReferenceGrad):
+                local_derivatives += 1
+                t, = t.ufl_operands
+            elif isinstance(t, Restricted):
+                assert restriction is None, "Got twice restricted terminal!"
+                restriction = t._side
+                t, = t.ufl_operands
+            elif t._ufl_terminal_modifiers_:
+                raise ValueError("Missing handler for terminal modifier type %s, object is %s." % (type(t), repr(t)))
+            else:
+                raise ValueError("Unexpected type %s object %s." % (type(t), repr(t)))
+        if not isinstance(t, Coefficient):
+            # Only split coefficients
+            return o
+        if t not in self._coefficient_split:
+            # Only split mixed coefficients
+            return o
+        # Reference value expected
+        assert reference_value
+        # Derivative indices
+        beta = indices(local_derivatives)
+        components = []
+        for subcoeff in self._coefficient_split[t]:
+            c = subcoeff
+            # Apply terminal modifiers onto the subcoefficient
+            if reference_value:
+                c = ReferenceValue(c)
+            for n in range(local_derivatives):
+                # Return zero if expression is trivially constant. This has to
+                # happen here because ReferenceGrad has no access to the
+                # topological dimension of a literal zero.
+                if is_cellwise_constant(c):
+                    dim = extract_unique_domain(subcoeff).topological_dimension()
+                    c = Zero(c.ufl_shape + (dim,), c.ufl_free_indices, c.ufl_index_dimensions)
+                else:
+                    c = ReferenceGrad(c)
+            if restriction == '+':
+                c = PositiveRestricted(c)
+            elif restriction == '-':
+                c = NegativeRestricted(c)
+            elif restriction == '|':
+                c = SingleValueRestricted(c)
+            elif restriction == '?':
+                c = ToBeRestricted(c)
+            elif restriction is not None:
+                raise RuntimeError(f"Got unknown restriction: {restriction}")
+            # Collect components of the subcoefficient
+            for alpha in numpy.ndindex(subcoeff.ufl_element().reference_value_shape):
+                # New modified terminal: component[alpha + beta]
+                components.append(c[alpha + beta])
+        # Repack derivative indices to shape
+        c, = indices(1)
+        return ComponentTensor(as_tensor(components)[c], MultiIndex((c,) + beta))
+
+    positive_restricted = modified_terminal
+    negative_restricted = modified_terminal
+    single_value_restricted = modified_terminal
+    to_be_restricted = modified_terminal
+    reference_grad = modified_terminal
+    reference_value = modified_terminal
+    terminal = modified_terminal
+
+
+def apply_coefficient_split(expr, coefficient_split):
+    """Split mixed coefficients, so mixed elements need not be
+    implemented.
+
+    :arg split: A :py:class:`dict` mapping each mixed coefficient to a
+                sequence of subcoefficients.  If None, calling this
+                function is a no-op.
+    """
+    if coefficient_split is None:
+        return expr
+    splitter = CoefficientSplitter(coefficient_split)
+    return map_expr_dag(splitter, expr)
+
+
+class FixedIndexRemover(MultiFunction):
+
+    def __init__(self, fimap):
+        MultiFunction.__init__(self)
+        self.fimap = fimap
+
+    expr = MultiFunction.reuse_if_untouched
+
+    def zero(self, o):
+        free_indices = []
+        index_dimensions = []
+        for i, d in zip(o.ufl_free_indices, o.ufl_index_dimensions):
+            if Index(i) in self.fimap:
+                ind_j = self.fimap[Index(i)]
+                if not isinstance(ind_j, FixedIndex):
+                    free_indices.append(ind_j.count())
+                    index_dimensions.append(d)
+            else:
+                free_indices.append(i)
+                index_dimensions.append(d)
+        return Zero(shape=o.ufl_shape, free_indices=tuple(free_indices), index_dimensions=tuple(index_dimensions))
+
+    def list_tensor(self, o):
+        rule = FixedIndexRemover(self.fimap)
+        cc = []
+        for o1 in o.ufl_operands:
+            comp = map_expr_dag(rule, o1)
+            cc.append(comp)
+        return ListTensor(*cc)
+
+    def multi_index(self, o):
+        return MultiIndex(tuple(self.fimap.get(i, i) for i in o.indices()))
+
+
+class IndexRemover(MultiFunction):
+
+    def __init__(self):
+        MultiFunction.__init__(self)
+
+    expr = MultiFunction.reuse_if_untouched
+
+    def _zero_simplify(self, o):
+        operand, = o.ufl_operands
+        rule = IndexRemover()
+        operand = map_expr_dag(rule, operand)
+        if isinstance(operand, Zero):
+            return Zero(shape=o.ufl_shape, free_indices=o.ufl_free_indices, index_dimensions=o.ufl_index_dimensions)
+        else:
+            return o._ufl_expr_reconstruct_(operand)
+
+    def indexed(self, o):
+        o1, i1 = o.ufl_operands
+        if isinstance(o1, ComponentTensor):
+            o2, i2 = o1.ufl_operands
+            fimap = dict(zip(i2.indices(), i1.indices(), strict=True))
+            rule = FixedIndexRemover(fimap)
+            v = map_expr_dag(rule, o2)
+            rule = IndexRemover()
+            return map_expr_dag(rule, v)
+        elif isinstance(o1, ListTensor):
+            if isinstance(i1[0], FixedIndex):
+                o1 = o1.ufl_operands[i1[0]._value]
+                rule = IndexRemover()
+                if len(i1) > 1:
+                    i1 = MultiIndex(i1[1:])
+                    return map_expr_dag(rule, Indexed(o1, i1))
+                else:
+                    return map_expr_dag(rule, o1)
+        rule = IndexRemover()
+        o1 = map_expr_dag(rule, o1)
+        return Indexed(o1, i1)
+
+    # Do something nicer
+    positive_restricted = _zero_simplify
+    negative_restricted = _zero_simplify
+    single_value_restricted = _zero_simplify
+    to_be_restricted = _zero_simplify
+    reference_grad = _zero_simplify
+    reference_value = _zero_simplify
+
+
+def remove_component_and_list_tensors(o):
+    if isinstance(o, Form):
+        integrals = []
+        for integral in o.integrals():
+            integrand = remove_component_list_tensors(integral.integrand())
+            if not isinstance(integrand, Zero):
+                integrals.append(integral.reconstruct(integrand=integrand))
+        return o._ufl_expr_reconstruct_(integrals)
+    else:
+        rule = IndexRemover()
+        return map_expr_dag(rule, o)

ufl/algorithms/compute_form_data.py

@@ -18,7 +18,7 @@
 from ufl.algorithms.apply_function_pullbacks import apply_function_pullbacks
 from ufl.algorithms.apply_geometry_lowering import apply_geometry_lowering
 from ufl.algorithms.apply_integral_scaling import apply_integral_scaling
-from ufl.algorithms.apply_restrictions import apply_default_restrictions, apply_restrictions, make_domain_restriction_map, make_domain_integral_type_map
+from ufl.algorithms.apply_restrictions import apply_default_restrictions, apply_restrictions, make_domain_restriction_map, make_domain_integral_type_map, apply_coefficient_split, remove_component_and_list_tensors
 from ufl.algorithms.check_arities import check_form_arity
 from ufl.algorithms.comparison_checker import do_comparison_check
 # See TODOs at the call sites of these below:
@@ -255,8 +255,6 @@ def compute_form_data(
 
     The default arguments configured to behave the way old FFC expects.
     """
-    from ufl.algorithms.apply_coefficient_split import apply_coefficient_split, remove_component_and_list_tensors
-
     # TODO: Move this to the constructor instead
     self = FormData()