[Cython] Beginner-friendly tickets

[Anoop Saldanha]

Thanks Kurt.  That was helpful.  Looks like the optimization is happening at
IterationTransform() in the pipeline.

On Wed, Mar 18, 2009 at 9:59 PM, Kurt Smith <kwmsmith at gmail.com> wrote:

> 2009/3/18 Anoop Saldanha <poonaatsoc at gmail.com>:
>
> [snip]
>
> >
> > But
> >
> > cdef int g():
> >      print "g called"
> >      return 5
> >
> > def f():
> >     cdef int i
> >     for i in range(g()):
> >         print i
> >     print i
> >
> > uses a ForFromStatNode for the "for in" loop!
>
> I'm not a core developer, so this is open to correction, but putting
> in some PrintTree() calls into
> Cython/Compiler/Main.py:create_pipeline() shows that it starts out as
> a ForInStatNode and is changed to a ForFromStatNode.  Perhaps because
> cython inferrs that g returns a C int and it triggers the 'range'
> optimization.
>
> Before any transformations:
>
> - (root): ModuleNode(pos=(foo.pyx:1:0))
>  - body: StatListNode(pos=(foo.pyx:1:0))
>    - stats[0]: CFuncDefNode(pos=(foo.pyx:1:5))
>     [removing cdef int g() stuff]
>    - stats[1]: DefNode(name="f")
>      - body: StatListNode(pos=(foo.pyx:6:4))
>        - stats[0]: CVarDefNode(pos=(foo.pyx:6:9))
>          - base_type: CSimpleBaseTypeNode(pos=(foo.pyx:6:9))
>          - declarators[0]: CNameDeclaratorNode(pos=(foo.pyx:6:13))
>        - stats[1]: ForInStatNode(pos=(foo.pyx:8:4)) <== starts out as
> as ForInStatNode
>          [snip rest of def f() function body]
>
> After all transformations:
>
> - (root): ModuleNode(pos=(foo.pyx:1:0))
>  - body: StatListNode(pos=(foo.pyx:1:0))
>    - stats[0]: CFuncDefNode(pos=(foo.pyx:1:5))
>       [snip func body]
>    - stats[1]: DefNode(name="f")
>      - body: StatListNode(pos=(foo.pyx:6:4))
>        - stats[0]: ForFromStatNode(pos=(foo.pyx:8:4))  <== Changed to
> a ForFromStatNode.
>          - target: NameNode(type=<CNumericType int>, name="i")
>          - bound1: IntNode(type=<CNumericType long>)
>          - bound2: SimpleCallNode(type=<CNumericType int>)
>            - function: NameNode(type=<CFuncType <CNumericType int>
> []>, name="g")
>          - step: IntNode(type=<CNumericType long>)
>          - body: StatListNode(pos=(foo.pyx:9:8))
>            - stats[0]: PrintStatNode(pos=(foo.pyx:9:8))
>              - arg_tuple: TupleNode(type=<PyTuple_Type>)
>                - args[0]: CoerceToPyTypeNode(type=<PyObjectType>)
>                  - arg: NameNode(type=<CNumericType int>, name="i")
>        - stats[1]: PrintStatNode(pos=(foo.pyx:10:4))
>          - arg_tuple: TupleNode(type=<PyTuple_Type>)
>            - args[0]: CoerceToPyTypeNode(type=<PyObjectType>)
>              - arg: NameNode(type=<CNumericType int>, name="i")
>
> Kurt
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>



-- 
Regards,
Anoop S.

People who says, "It's not winning or losing that matters, but
participation", probably lost.
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