Dear developers,
I was looking through the class DifferentialForm, and there is a note in
the `__eq__` method pointing that "...most of the execution time is spent"
in cleaningpu the differential forms
def __eq__(self, other):
if type(other) == type(self):
if self._degree != other._degree:
return False
else:
# TODO: the following two lines are where most of the
# execution time is spent.
self._cleanup()
other._cleanup()
if len(self._components) != len(other._components):
return False
# We compare the component dictionary of both differential
# forms, keeping in mind that the set of keys is
# lexicographically ordered, so that we can simply iterate
# over both dictionaries in one go and compare (key, value)
# pairs as we go along.
for (key1, val1), (key2, val2) in \
zip(self._components.iteritems(), \
other._components.iteritems()):
if key1 != key2 or str(val1) != str(val2):
return False
return True
else:
return False
Then, I found the `_cleanup` method
def _cleanup(self):
r"""
Helper function to clean up self, i.e. to remove any
zero components from the dictionary of components.
EXAMPLES::
sage: F = DifferentialForms()
sage: f = DifferentialForm(F, 1)
sage: f[0] = 0
sage: f[1] = 1
sage: f[2] = 0
sage: f._dump_all()
{(2,): 0, (0,): 0, (1,): 1}
sage: f._cleanup()
sage: f._dump_all()
{(1,): 1}
"""
zeros = []
for comp in self._components:
if self._components[comp].is_zero():
zeros.append(comp)
for comp in zeros:
del self._components[comp]
And I wonder... Is it possible to delete directly the `zeros` from `self`?
I guess it was not done like that because it is not possible!
However, then it occur to me that copying `self` to `other` and then
reassign to `self` only the notzero component could be faster
Is it possible?
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