Re: [Cython] [cython-users] freelist benchmarks

[Stefan Behnel]

Hi,

thanks for looking through it.

David Roe, 25.02.2013 00:00:
> I changed the current type pointer check to look at tp_basicsize instead.
> 
>> That made it work for almost all classes in lxml's own Element hierarchy,
>> with only a couple of exceptions in lxml.objectify that have one additional
>> object field. So, just extending the freelist support to use two different
>> lists for different struct sizes instead of just one would make it work for
>> all of lxml already. Taking a look at Sage to see how the situation appears
>> over there would be interesting, I guess.
> 
> I found some chains of length 5.  This could be shortened to 4 by putting
> the freelist at the level of Element (which is where you most care about
> speed of object creation).

It's substantially easier to keep it in the top-level base class, though.
Otherwise, we'd need a new protocol between inheriting types as I
previously described. That add a *lot* of complexity.


> SageObject
> -> Element (_parent attribute and cdef methods)
> -> Vector (_degree)
> -> FreeModuleElement (_is_mutable)
> -> FreeModuleElement_generic_dense (_entries)
> 
> SageObject
> -> Element (_parent attribute and cdef methods)
> ->sage.structure.element.Matrix (_nrows)
> -> sage.matrix.matrix.Matrix (_base_ring)
> -> Matrix_integer_dense (_entries)

Ok, so even for something as large as Sage, we'd apparently end up with
just a couple of freelists for a given base type. That really makes it
appear reasonable to make that number a compile time constant as well. I
mean, even if you *really* oversize it, all you loose is the static memory
for a couple of pointers. On a 64 bit system, if you use a freelist size of
8 objects and provision freelists for 8 differently sized subtypes, that's
8*8*8 bytes in total, or half a KB, statically allocated. Even a hundred
times that size shouldn't hurt anyone. Unused subtype freelists really take
almost no space and won't hurt performance either.


> This does look cool to have though.

It definitely is.

Stefan

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[Cython] No matching signature with fused memoryview and None default

[Dave Hirschfeld]

With the following code I get a "No matching signature found" error.
Is this a bug?

```
%%cython
cimport cython

ctypedef fused floating:
cython.double
cython.float


def nosignature(floating[:] x, floating[:] myarray = None):
print myarray is None
return x
```

In [39]: nosignature(ones(1, dtype=np.float32), ones(1, dtype=np.float32))
False
Out[39]: 

In [40]: nosignature(ones(1, dtype=np.float64), ones(1, dtype=np.float64))
False
Out[40]: 

In [41]: nosignature(ones(1, dtype=np.float64))
True
Out[41]: 

In [42]: nosignature(ones(1, dtype=np.float32))

---
TypeError Traceback (most recent call last)
 in ()
> 1 nosignature(ones(1, dtype=np.float32))

ca9.pyd in ca9.__pyx_fused_cpdef ca9.c:2282)()

TypeError: No matching signature found




Thanks,
Dave

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