def product(*args, **kwargs):
"""Product of multiple :py:class:`MonomialSum`s"""
rename_map = kwargs.pop('rename_map', None)
if rename_map is None:
rename_map = make_rename_map()
if kwargs:
raise ValueError("Unrecognised keyword argument: " + kwargs.pop())
result = MonomialSum()
for monomials in product(*args):
renamer = make_renamer(rename_map)
sum_indices = []
atomics = []
rest = one
for s, a, r in monomials:
s_, applier = renamer(s)
sum_indices.extend(s_)
atomics.extend(map(applier, a))
rest = Product(applier(r), rest)
result.add(sum_indices, atomics, rest)
return result
def product(*args, **kwargs):
"""Product of multiple :py:class:`MonomialSum`s"""
rename_map = kwargs.pop('rename_map', None)
if rename_map is None:
rename_map = make_rename_map()
if kwargs:
raise ValueError("Unrecognised keyword argument: " + kwargs.pop())
result = MonomialSum()
for monomials in product(*args):
renamer = make_renamer(rename_map)
sum_indices = []
atomics = []
rest = one
for s, a, r in monomials:
s_, applier = renamer(s)
sum_indices.extend(s_)
atomics.extend(map(applier, a))
rest = Product(applier(r), rest)
result.add(sum_indices, atomics, rest)
return result
def _collect_monomials(expression, self):
"""Refactorises an expression into a sum-of-products form, using
distributivity rules (i.e. a*(b + c) -> a*b + a*c). Expansion
proceeds until all "compound" expressions are broken up.
:arg expression: a GEM expression to refactorise
:arg self: function for recursive calls
:returns: :py:class:`MonomialSum`
:raises FactorisationError: Failed to break up some "compound"
expressions with expansion.
"""
# Phase 1: Collect and categorise product terms
def stop_at(expr):
# Break up compounds only
return self.classifier(expr) != COMPOUND
common_indices, terms = traverse_product(expression, stop_at=stop_at)
common_indices = tuple(common_indices)
common_atomics = []
common_others = []
compounds = []
for term in terms:
label = self.classifier(term)
if label == ATOMIC:
common_atomics.append(term)
elif label == COMPOUND:
compounds.append(term)
elif label == OTHER:
common_others.append(term)
else:
raise ValueError("Classifier returned illegal value.")
common_atomics = tuple(common_atomics)
# Phase 2: Attempt to break up compound terms into summands
sums = []
for expr in compounds:
summands = traverse_sum(expr, stop_at=stop_at)
if len(summands) <= 1 and not isinstance(expr,
(Conditional, MathFunction)):
# Compound term is not an addition, avoid infinite
# recursion and fail gracefully raising an exception.
raise FactorisationError(expr)
# Recurse into each summand, concatenate their results
sums.append(MonomialSum.sum(*map(self, summands)))
# Phase 3: Expansion
#
# Each element of ``sums`` is a MonomialSum. Expansion produces a
# series (representing a sum) of products of monomials.
result = MonomialSum()
for s, a, r in MonomialSum.product(*sums, rename_map=self.rename_map):
renamer = make_renamer(self.rename_map)
renamer(common_indices) # update current_set
s_, applier = renamer(s)
all_indices = common_indices + s_
atomics = common_atomics + tuple(map(applier, a))
# All free indices that appear in atomic terms
atomic_indices = set().union(
*[atomic.free_indices for atomic in atomics])
# Sum indices that appear in atomic terms
# (will go to the result :py:class:`Monomial`)
sum_indices = tuple(index for index in all_indices
if index in atomic_indices)
# Sum indices that do not appear in atomic terms
# (can factorise them over atomic terms immediately)
rest_indices = tuple(index for index in all_indices
if index not in atomic_indices)
# Not really sum factorisation, but rather just an optimised
# way of building a product.
rest = sum_factorise(rest_indices, common_others + [applier(r)])
result.add(sum_indices, atomics, rest)
return result
def _collect_monomials(expression, self):
"""Refactorises an expression into a sum-of-products form, using
distributivity rules (i.e. a*(b + c) -> a*b + a*c). Expansion
proceeds until all "compound" expressions are broken up.
:arg expression: a GEM expression to refactorise
:arg self: function for recursive calls
:returns: :py:class:`MonomialSum`
:raises FactorisationError: Failed to break up some "compound"
expressions with expansion.
"""
# Phase 1: Collect and categorise product terms
def stop_at(expr):
# Break up compounds only
return self.classifier(expr) != COMPOUND
common_indices, terms = traverse_product(expression, stop_at=stop_at)
common_indices = tuple(common_indices)
common_atomics = []
common_others = []
compounds = []
for term in terms:
label = self.classifier(term)
if label == ATOMIC:
common_atomics.append(term)
elif label == COMPOUND:
compounds.append(term)
elif label == OTHER:
common_others.append(term)
else:
raise ValueError("Classifier returned illegal value.")
common_atomics = tuple(common_atomics)
# Phase 2: Attempt to break up compound terms into summands
sums = []
for expr in compounds:
summands = traverse_sum(expr, stop_at=stop_at)
if len(summands) <= 1:
# Compound term is not an addition, avoid infinite
# recursion and fail gracefully raising an exception.
raise FactorisationError(expr)
# Recurse into each summand, concatenate their results
sums.append(MonomialSum.sum(*map(self, summands)))
# Phase 3: Expansion
#
# Each element of ``sums`` is a MonomialSum. Expansion produces a
# series (representing a sum) of products of monomials.
result = MonomialSum()
for s, a, r in MonomialSum.product(*sums, rename_map=self.rename_map):
renamer = make_renamer(self.rename_map)
renamer(common_indices) # update current_set
s_, applier = renamer(s)
all_indices = common_indices + s_
atomics = common_atomics + tuple(map(applier, a))
# All free indices that appear in atomic terms
atomic_indices = set().union(*[atomic.free_indices
for atomic in atomics])
# Sum indices that appear in atomic terms
# (will go to the result :py:class:`Monomial`)
sum_indices = tuple(index for index in all_indices
if index in atomic_indices)
# Sum indices that do not appear in atomic terms
# (can factorise them over atomic terms immediately)
rest_indices = tuple(index for index in all_indices
if index not in atomic_indices)
# Not really sum factorisation, but rather just an optimised
# way of building a product.
rest = sum_factorise(rest_indices, common_others + [applier(r)])
result.add(sum_indices, atomics, rest)
return result
