[pypy-dev] Should jitviewer come with a warning?

[Maciej Fijalkowski]

On Sun, Feb 3, 2013 at 10:12 PM, Maciej Fijalkowski <fijall at gmail.com> wrote:
> On Sun, Feb 3, 2013 at 10:08 PM, John Camara <john.m.camara at gmail.com> wrote:
>>> What makes you think people will even read this warning, let alone
>>> prioritize it over their immediate desire to make their program run
>>> faster?
>>
>>> (Not that I am objecting to adding the warning, but I think you might be
>>> fooling yourself if you think it will have any impact)
>>
>>> Jean-Paul
>>
>> I agree with you and was not being naive and thinking this alone was going
>> to solve the problem but it does gives us something to point to when we see
>> someone abusing the jitviewer.
>>
>> Maybe, a more effective approach, is not to advertise about the jitviewer to
>> everyone who has performance issues and only tell those who are experience
>> programmers who have already done the obvious in fixing any design issues
>> that had existed in their code.  Having inexperience developers use the
>> normal profiling tools will still help them find the hot spots in their code
>> and help prevent them from picking up habits that lead them to writing
>> un-Pythonic code.
>>
>> I'm sure we all agree that code with a better design will run faster in pypy
>> than trying to add optimizations that work only for pypy to help out a poor
>> design.
>>
>> I don't think we want to end up with a lot of Python code that looks like C
>> code.  This is what happens when the inexperience start relying on the
>> jitviewer.
>>
>> For instance take a look at this code [1] and blog [2] which lead me to post
>> this. This is not the first example I have come across this issue and
>> unfortunately it appears to be increaseing at an alarming rate.
>>
>> I guess I feel we have a responsibility to try to promote good programming
>> practices when we can.
>>
>> [1] -
>> https://github.com/msgpack/msgpack-python/blob/master/msgpack/fallback.py
>>
>> [2] - http://blog.affien.com/archives/2013/01/29/msgpack-for-pypy/
>>
>> John
>>
>>
>>
>> On Sun, Feb 3, 2013 at 12:39 PM, John Camara <john.m.camara at gmail.com>
>> wrote:
>>>
>>> I have been noticing a pattern where many who are writing Python code to
>>> run on PyPy are relying more and more on using the jitviewer to help them
>>> write faster code.  Unfortunately, many of them who do so don't look at
>>> improving the design of their code as a way to improve the speed at which it
>>> will run under PyPy but instead start writing obscure Python code that
>>> happens to run faster under PyPy.
>>>
>>> I know that at least with the PyPy core developers they would like to see
>>> every one just create good clean Python code and that often code that has
>>> been made into obscure Python was don so to try to optimize it for CPython
>>> which in many cases causes it to run slower on PyPy than it would run it the
>>> code just followed typical Python idioms.
>>>
>>> I feel that a normal developer should be using tools like cProfiler and
>>> runsnakerun and cleaning up design issues way before they should even
>>> consider using jitviewer.
>>>
>>> In a recent case where I saw someone using the jitviewer who likely
>>> doesn't need to use it.  At least they don't need to use it considering the
>>> current design of the code I said the following
>>>
>>> "The jitviewer should be mainly used by PyPy core developers and those
>>> building PyPy VMs. A normal developer writing Python code to run on PyPy
>>> shouldn’t have a need to use it. They can use it to point out an
>>> inefficiency that PyPy has to the core developers but it should not be used
>>> as a way to get you to write Python code in a way that has a better chance
>>> of being optimized under PyPy except for very rare occasions and even then
>>> it should only be made by those who follow closely and understand PyPy’s
>>> development."
>>>
>>>
>>> Do others here share this same opinion and should some warning be added to
>>> the jitviewer?
>>>
>>> John
>>
>>
>>
>> _______________________________________________
>> pypy-dev mailing list
>> pypy-dev at python.org
>> http://mail.python.org/mailman/listinfo/pypy-dev
>>
>
> Hi John.
>
> I don't believe jitviewer is advertised really in that many places. We
> tell people who come to IRC, yes, but that's about it (it's not
> prominently featured on pypy.org for example). It's hard enough to
> make people read docs.

Also, looking at the msgpack - this code is maybe not ideal, but if
you're dealing with buffer-level protocols, you end up with code
looking like C a lot.