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Fix numba.typed.List extend for singleton and empty iterable #5517

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merged 5 commits into from
Apr 23, 2020
Merged

Fix numba.typed.List extend for singleton and empty iterable #5517

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6c3daac
fix refinement on extend
esc Apr 7, 2020
80a0a88
fix for extend on empty iterable
esc Apr 7, 2020
efb58c6
fix extending a refined list
esc Apr 7, 2020
0f13328
rename test to avoid ambiguities
esc Apr 14, 2020
d8119b6
simplify logic
esc Apr 20, 2020
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27 changes: 27 additions & 0 deletions numba/tests/test_typedlist.py
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Original file line number Diff line number Diff line change
Expand Up @@ -729,6 +729,33 @@ def impl():
got = impl()
self.assertEqual(expected, got)

def test_extend_single_value_container(self):
@njit
def impl():
l = List()
l.extend((100,))
return l

expected = impl.py_func()
got = impl()
self.assertEqual(expected, got)

def test_extend_empty_unrefined(self):
# Extending an unrefined list with an empty iterable doesn't work in a
# jit compiled function as the list remains untyped.
l = List()
l.extend(tuple())
self.assertEqual(len(l), 0)
Comment on lines +744 to +748
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Is this behaviour a good idea? What about JIT transparency etc.

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Also, if you put this in a JIT compiled function, you get:

Invalid use of Function(<function impl_extend at 0x7f5648715c10>) with argument(s) of type(s): (ListType[undefined], Tuple())
 * parameterized
In definition 0:
    TypingError: extend argument must be iterable

empty tuples are iterable, this is a bit confusing. I think it's arising because an empty tuple is typed as Tuple at present, which is not iterable for Numba's purposes.

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Yeah, I think only UniTuple is iterable. I struggled with this one for some time and came to the conclusion that this is a corner case that only works outside of a jit context.

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So, even if tuple() would be something iterable, the function would not compile as the list can not be refined.

self.assertFalse(l._typed)

def test_extend_empty_refiend(self):
# Extending a refined list with an empty iterable doesn't work in a
# jit compiled function as the (empty) argument can't be typed
l = List((1,))
l.extend(tuple())
self.assertEqual(len(l), 1)
self.assertTrue(l._typed)


@njit
def cmp(a, b):
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15 changes: 13 additions & 2 deletions numba/typed/typedlist.py
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Original file line number Diff line number Diff line change
Expand Up @@ -356,13 +356,24 @@ def pop(self, i=-1):

def extend(self, iterable):
if not self._typed:
iterable_length = len(iterable)
# Empty iterable, do nothing
if iterable_length == 0:
return self
# Need to get the first element of the iterable to initialise the
# type of the list. FIXME: this may be a problem if the iterable
# can not be sliced.
self._initialise_list(iterable[0])
self.append(iterable[0])
return _extend(self, iterable[1:])
return _extend(self, iterable)
# Iterable has more values to extend from
if iterable_length > 1:
return _extend(self, iterable[1:])
else:
return self
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Could this just be:

            self._initialise_list(iterable[0])
            return _extend(self, iterable)

i.e. init type, then extend, is there a need to append then slice from 1?

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Yes, this can be significantly simplified.

elif len(iterable) == 0:
return self
else:
return _extend(self, iterable)

def remove(self, item):
return _remove(self, item)
Expand Down