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

[Fabian, Nathan]

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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