[Insight-developers] Changing ImageRegionMultidimensionalSplitter

[Bill Lorensen]

Eventually, we could add alternate splitting policies, keeping the
current one as a default. For now, I agree that the documentation
should be fixed.

And, we need to get the failing tests to pass. They are hiding other failures.

Bill

On Sat, Aug 15, 2009 at 12:52 PM, Luis Ibanez<luis.ibanez at kitware.com> wrote:
> I would vote for
>
> a)  fixing the documentation. (which is backward compatible), and
>
> b) if we need an alternative splitting algorithm:
>     then refactor this  in ITK 4.0.
>
>
> My 2 cents,
>
>
>      Luis
>
>
> --------------------------------------------------------------------------------
>
> On Wed, Aug 12, 2009 at 10:12 AM, Bradley Lowekamp <blowekamp at mail.nih.gov>
> wrote:
>>
>> Hello,
>> I am looking for agreement that this will be a good solution, with
>> acceptable backwards compatibility.
>> Looking into the following bug:
>> http://www.itk.org/Bug/view.php?id=8524
>> I discovered the methods do not meet the documentation. And that the
>> general approach to multi-dimensional splitting can not meet the
>> requirements of the documentation. This class is designed to work with the
>> StreamingImageFilter, and is currently not functional under many conditions.
>> To illustrate one of the problem consider the case where the Region to be
>> split is [100,100,1] and the requested number of splits is 100:
>>
>> http://www.cdash.org/CDash/viewCoverageFile.php?buildid=400312&fileid=10857899
>> When the number of splits is reduced we will not get the same number of
>> splits for the two methods. These are the lines not covered.
>>
>>   /** How many pieces can the specifed region be split? A given region
>>    * cannot always be divided into the requested number of pieces.  For
>>    * instance, if the numberOfPieces exceeds the number of pixels along
>>    * a certain dimensions, then some splits will not be possible. This
>>    * method returns a number less than or equal to the requested number
>>    * of pieces.  */
>>   virtual unsigned int GetNumberOfSplits(const RegionType &region,
>>                                          unsigned int requestedNumber);
>>   /** Get a region definition that represents the ith piece a specified
>> region.
>>    * The "numberOfPieces" specified should be less than or equal to what
>>    * GetNumberOfSplits() returns. */
>>   virtual RegionType GetSplit(unsigned int i, unsigned int numberOfPieces,
>>                               const RegionType &region);
>>
>> -Proposed Solution-
>> 1) Change Documentation
>>   /** Get a region definition that represents the ith piece a specified
>> region.
>>    * The "numberOfPieces" specified must be equal to what
>>    * GetNumberOfSplits() returns. */
>>   virtual RegionType GetSplit(unsigned int i, unsigned int numberOfPieces,
>>                               const RegionType &region);
>> 2) New algorithm for Multi-dimensional splitting
>> Instead of taking the nth root and shrinking the splits in each dimension,
>> the new approach will be:
>> iteratively split the dimension who's splitted region is the largest. This
>> will be reproducible between the two methods.
>>
>> Any problems with this solution?
>> Thanks,
>> Brad
>>
>> ========================================================
>>
>> Bradley Lowekamp
>>
>> Lockheed Martin Contractor for
>>
>> Office of High Performance Computing and Communications
>>
>> National Library of Medicine
>>
>> blowekamp at mail.nih.gov
>>
>>
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>
>
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