[Cython] Too many instantiations with fused type memoryviews

2014-03-08 Thread Pauli Virtanen 
Hi,

FYI: Cython instantiates fused type routines with memoryview arguments
unnecessarily many times.

Example:
```
ctypedef fused idx_t:
short
long

# Cython 0.20.1 instantiates this function 128 times,
# even though only 2 would be needed
def fubar_128(idx_t[:] a,
  idx_t[:] b,
  idx_t[:] c,
  idx_t[:] d,
  idx_t[:] e,
  idx_t[:] f,
  idx_t[:] g):
print("HALLO")

def fubar_2(idx_t a,
idx_t b,
idx_t c,
idx_t d,
idx_t e,
idx_t f,
idx_t g):
print("HULLO")
```
$ cython cymod.pyx
$ cython --version
Cython version 0.20.1
$ grep -c 'print("HALLO")' cymod.c
128
$ grep -c 'print("HULLO")' _cymod.c
2

The n**m explosion starts to hurt quite quickly when there are several
array arguments and more than one fused type. I think this issue is
also accompanied by some signature resolution bugs (I'll try to come
up with an example case).


Cheers,

-- 
Pauli Virtanen

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Re: [Cython] Too many instantiations with fused type memoryviews

2014-03-08 Thread Stefan Behnel 
Pauli Virtanen, 08.03.2014 21:11:
> FYI: Cython instantiates fused type routines with memoryview arguments
> unnecessarily many times.
> 
> Example:
> ```
> ctypedef fused idx_t:
> short
> long
> 
> # Cython 0.20.1 instantiates this function 128 times,
> # even though only 2 would be needed
> def fubar_128(idx_t[:] a,
>   idx_t[:] b,
>   idx_t[:] c,
>   idx_t[:] d,
>   idx_t[:] e,
>   idx_t[:] f,
>   idx_t[:] g):
> print("HALLO")
> 
> def fubar_2(idx_t a,
> idx_t b,
> idx_t c,
> idx_t d,
> idx_t e,
> idx_t f,
> idx_t g):
> print("HULLO")
> ```
> $ cython cymod.pyx
> $ cython --version
> Cython version 0.20.1
> $ grep -c 'print("HALLO")' cymod.c
> 128
> $ grep -c 'print("HULLO")' _cymod.c
> 2
> 
> The n**m explosion starts to hurt quite quickly when there are several
> array arguments and more than one fused type. I think this issue is
> also accompanied by some signature resolution bugs (I'll try to come
> up with an example case).

Yes, this is a known problem. The work-around is to ctypedef the memory
view type, not just the dtype.

http://thread.gmane.org/gmane.comp.python.cython.user/10437

Stefan

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Re: [Cython] Too many instantiations with fused type memoryviews

2014-03-08 Thread Pauli Virtanen 
08.03.2014 22:40, Stefan Behnel kirjoitti:
[clip]
> Yes, this is a known problem. The work-around is to ctypedef the
> memory view type, not just the dtype.
> 
> http://thread.gmane.org/gmane.comp.python.cython.user/10437

Thanks, I missed that.

Re: arguments in the previous thread --- I think it would indeed be
better if memoryviews would not invoke cross-product behavior. If
scalars work in one way, also arrays should work in the same way.

Pauli


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