[Cython] AddTraceback() slows down generators

[mark florisson]

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?