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accelerate setitem with slice
When using setitem with a slice and an item that is smaller than the slice, we need to remove items. Until now, this was done with pop, which actually incurred a memory move of the tail of the list for every item being removed. Now that we can mass delete items in the list with `del` and slices, we used that functionality instead.
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Lines changed: 2 additions & 10 deletions

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‎numba/listobject.py‎

Lines changed: 2 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -677,16 +677,8 @@ def impl_slice(l, index, item):
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slice_range.start + len(item))
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for i,j in zip(replace_range, item):
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l[i] = j
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# pop the remaining ones
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pop_range = range(slice_range.start + len(item),
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slice_range.stop)
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# pop will mutate the list, so we always need to pop the
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# same index
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k = slice_range.start + len(item)
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for _ in pop_range:
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# FIXME: This may be slow. Each pop can incur a
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# memory copy of one or more items.
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l.pop(k)
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# delete remaining ones
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del l[slice_range.start + len(item):slice_range.stop]
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# Extended slices
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else:
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if len(slice_range) != len(item):

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