Hi Stefan,
On 5 July 2014 11:34, Stefan Behnel <stefan...@behnel.de> wrote:
> Hi,
>
> I started optimising cascaded assignments a little to reduce the
> unnecessary duplication of coercions. While doing that, I found this test
> in memslice.pyx:
>
> '''
> def cascaded_buffer_assignment(obj):
> """
> >>> A = IntMockBuffer("A", range(6))
> >>> cascaded_buffer_assignment(A)
> acquired A
> acquired A
> released A
> released A
> """
> cdef int[:] a, b
> a = b = obj
> '''
>
> It's explicitly tested for that we create two independent memory views in
> this case. Is there an actual reason for this? As long as the types of a
> and b are identical, I don't see why we would want to request the buffer
> twice.
I think it's mostly for simplicity, since any reaching definition is
cleared at the end of the function. Are you thinking to generally
implement this? I suppose you could assign the coercion to a new
variable and replace all use sites (e.g. all the coercions in the
cascaded assignment) with that variable.
obj = ...
a = coerce obj int[:]
b = coerce obj int[:]
->
obj = ...
tmp = coerce obj int[:]
a = tmp
b = tmp
These transformations may be easier on a three-address code-like
representation, where this sort of replacement can be more effective
in SSA form or by first applying copy propagation. Perhaps if the
coercion was explicit a CSE pass could even eliminate any duplicates.
Cheers,
Mark
> Stefan
> _______________________________________________
> cython-devel mailing list
> cython-devel@python.org
> https://mail.python.org/mailman/listinfo/cython-devel
_______________________________________________
cython-devel mailing list
cython-devel@python.org
https://mail.python.org/mailman/listinfo/cython-devel
