[Pyrex] Sequence patches from Paul Prescod

[Robert Bradshaw]

Interesting. I assume one declares a sequence as

cdef sequence my_list

I don't see PySequence_Check being used, I assume it is up to the  
developer to only assign list/tuple/sequence-supporting objects to  
such declared variables? It looks like PySequence_GetItem does  
perform a check though.

In our SageX fork, we've implemented a runtime check for all indexing  
(with respect to a c int) and if it is a list/tuple with a valid  
index, the macro form is called. The checks are all macros too, so  
when indexing into a list or tuple (by far the most common case, at  
least in our codebase) we avoid any function calls (let alone the  
almost a dozen required for boxing an integer and using the generic  
PyObject_GetItem). It is much, much faster.

A similar trick is used in for loops and list comprehensions. You can  
look at it at http://sagemath.org/packages/standard/ (spkg is just a  
bzipped tar file)

- Robert

On Jun 4, 2007, at 1:57 PM, Jim Kleckner wrote:

> Looking at Pyrex-generated code, I see boxing of integer
> types when indexing into sequence types that seems avoidable.
>
> After digging, I noticed Paul Prescod's patches for sequences
> that are documented here:
>
>  http://www.prescod.net/python/pyrexopt/pyrex_sequences.diff
>
> What was the status of this discussion?  It seems like a
> relatively clean patch.  Is there some reason I should avoid it?
>
> Jim
>
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