[Paraview-developers] [vtk-developers] change to vtkExodusIIReaderPrivate::ResetCache()

[Moreland, Kenneth]

Have not at all looked at the code, but it sounds like a job the
vtkWeakPointer was designed for.

-Ken

   ****      Kenneth Moreland
    ***      Sandia National Laboratories
***********  
*** *** ***  email: kmorel at sandia.gov
**  ***  **  phone: (505) 844-8919
    ***      web:   http://www.cs.unm.edu/~kmorel




On 4/26/11 6:48 PM, "Fabian, Nathan" <ndfabia at sandia.gov> wrote:

>I just found an issue where the polygon code was assuming the cache was
>valid after a second call (which destroyed the array from the previous
>call). 
>
>I added Register/Unregister to keep the array.  Which may not really be
>any safer. What is the proper response?  Call out to GetCacheOrRead each
>time an array is used?
>
>I haven't really carefully audited the code, but in general it does look
>like GetCacheOrRead is called once and then that array is used immediately
>after, but I could see this cropping up again...
>
>On 4/25/11 12:21 PM, "David Thompson" <dcthomp at sandia.gov> wrote:
>
>>> From a pull from master some weeks ago, the previous version of this
>>> method looked like this:
>>> ...
>>> When reading in an exodus file now, the code disappears into the
>>> reader and never finishes (maybe it would eventually, but after a
>>> long while I kill it).  Adding back in the line to set the cache
>>> capacity to 128 resolves this issue.  I expect that the line was
>>> removed for a reason.  Did removing the line resolve a problem for
>>> someone else?  Is anyone else having difficulty with the exodus
>>> reader as a result of this change?  Or is it something specific to
>>> my exodus file/runtime environment?
>>
>>Hi Pat,
>>
>>The line was removed to address a problem Alan had reported when
>>opening many small files with the parallel reader... the sum of the
>>caches (one from each sub-reader owned by the parallel reader) was
>>growing too large. I haven't heard whether anyone else is having
>>problems but Alan reported it fixed his issue. If I had to guess, I
>>would say there's some code in there relying on the cache holding on
>>to a reference to a vtkDataArray when it should not (even with a
>>128MiB cache, there was never any guarantee). If so, valgrind should
>>pick up on the reference to freed memory. Can you run your code
>>through valgrind and see if it complains?
>>
>>    David
>>
>>
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>
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