[Cython] [sage-devel] Re: Locally scoped dynamic memory (in SAGE and elsewhere)

[Michael.Abshoff]

William Stein wrote:
> On Thu, Apr 10, 2008 at 10:02 AM, Michael.Abshoff
> <michael.abshoff at googlemail.com> wrote:
>>  > But, test test suite doesn't test for all of the odd input that users
>>  > will feed to sage.  These are the cases that will leak memory and
>>  > there is not possible way to test for all of them.  Also debugging
>>  > memory leaks is super nasty.  Compared to that pain, having a slightly
>>  > slower memory allocator is not a big deal.
>>
>>  Well, as long as you write code in C memory leaks when something goes
>>  wrong is something you have to live with. And python is far from perfect
>>  regarding memory management too IMHO as I point out above. Another issue
>>  is that once we have extensions that do work with threads we no longer
>>  can use Python's allocation since it isn't thread safe.
>>
>>  Adding some more checks to the Sage codebase around allocations is
>>  something that ought to be done, but on the list of things to fix
>>  potential memory leaks from garbage input is low on the list of my
>>  personal priority as long as we have real leaks to deal with. Feel free
>>  to try out the above and report back if it fixes issues and how much of
>>  an impact on performance it has.
>>
> 
> Just for the record, I think Brian isn't suggesting we do anything
> differently with Sage.  He's writing lots of _new_ code using
> Cython for his distributed matrix arrays project, and ran into this problem,
> and thought -- surely the Sage folks have solved this.  Then he looked
> at our code for "the solution" and noticed that we haven't.

Yes, without a doubt, but I am skeptical that that solution would work 
[Brian never claimed it did and actually raised that concern].

> That said, this is definitely not the most important thing for *us*
> to worry about at this point.    We have many more important
> problems to solve first.   But I'm really glad Brian is raising this
> issue, etc.
> 

Sure and it is certainly good to be discussed. I didn't want to be 
dismissive about the idea, it is just that I have been in the "debugging 
memory leaks in Cython extension" trenches for the last eight months and 
hence I do not trust python or its memory management at all any more. 
And having been burned over and over again has left me the way I am ;)

>  -- William

Cheers,

Michael

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