[Cython] AddTraceback() slows down generators

[mark florisson]

On 28 January 2012 19:59, Vitja Makarov <vitja.makarov at gmail.com> wrote:
> 2012/1/28 mark florisson <markflorisson88 at gmail.com>:
>> On 28 January 2012 19:48, mark florisson <markflorisson88 at gmail.com> wrote:
>>> On 28 January 2012 19:41, Vitja Makarov <vitja.makarov at gmail.com> wrote:
>>>> 2012/1/28 Stefan Behnel <stefan_ml at behnel.de>:
>>>>> Stefan Behnel, 27.01.2012 09:02:
>>>>>> any exception *propagation* is
>>>>>> still substantially slower than necessary, and that's a general issue.
>>>>>
>>>>> Here's a general take on a code object cache for exception propagation.
>>>>>
>>>>> https://github.com/scoder/cython/commit/ad18e0208
>>>>>
>>>>> When I raise an exception in test code that propagates through a Python
>>>>> call hierarchy of four functions before being caught, the cache gives me
>>>>> something like a 2x speedup in total. Not bad. When I do the same for cdef
>>>>> functions, it's more like 4-5x.
>>>>>
>>>>> The main idea is to cache the objects in a reallocable C array and bisect
>>>>> into it based on the C code "__LINE__" of the exception, which should be
>>>>> unique enough for a given module.
>>>>>
>>>>> It's a global cache that doesn't limit the lifetime of code objects  (well,
>>>>> up to the lifetime of the module, obviously). I don't know if that's a
>>>>> problem because the number of code objects is only bounded by the number of
>>>>> exception origination points in the C source code, which is usually quite
>>>>> large. However, only a tiny fraction of those will ever raise or propagate
>>>>> an exception in practice, so the real number of cached code objects will be
>>>>> substantially smaller.
>>>>>
>>>>> Maybe thorough test suites with lots of failure testing would notice a
>>>>> difference in memory consumption, even though a single code objects isn't
>>>>> all that large either...
>>>>>
>>>>> What do you think?
>>>>>
>>>>
>>>> We already have --no-c-in-traceback flag that disables C line numbers
>>>> in traceback.
>>>> What's about enabling it by default?
>>>>
>>>> --
>>>> vitja.
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>>>
>>> I'm quite attached to that feature actually :), it would be pretty
>>> annoying to disable that flag every time. And what would disabling
>>> that option gain, as the current code still formats the filename and
>>> function name.
>>
>> Ah, you mean it would cache less code objects for multiple possible
>> errors in expressions (or statements) on a single source line?
>
> Not exactly. I mean PyString_Format() is called to add C filename and
> C lineno to python function name.
>

Ah indeed, the source lineno is only added to the code object of course.

> --
> vitja.
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