[Insight-developers] ImageRegion bounds caching

[Williams, Norman K]

No you were clear -- maybe I wasn't clear ;-)

If you start testing for NaNs, it would be good if there was a way to test
for them that doesn't cause a numerical exception, if
ITK_USE_FLOATINGPOINTEXCEPTIONS is turned on.

This might be tricky, because in my experience, anything you do with bad
numeric values will throw an exception. In particular the case you
mentioned:

> ImageRegion::IsInside ContinousIndex ) does return false for NaN, but
> only because NaN is cast to integer which yields a massive negative
> number that is out of bounds.


assigning (double)NaN to an integer would throw an exception.


On 3/2/11 2:05 PM, "M Stauffer (V)" <mstauff at verizon.net> wrote:

>Hi,
>
>I think I wasn't clear. We're not trying to catch NaN exceptions or
>explicitly identify NaN's. But rather we want ImageRegion::IsInside to
>return false when a NaN is present in the input index.
>
>We first saw a problem in ImageFunction::IsInsideBuffer, which was
>returning true for indecies containing one or more NaN's. I submitted a
>separate patch to fix it to return false when NaN's are in the input
>index.
>See http://review.source.kitware.com/#change,1110
>
>Cheers,
>Michael
>
>>-----Original Message-----
>>From: Williams, Norman K [mailto:norman-k-williams at uiowa.edu]
>>Sent: Tuesday, March 01, 2011 4:47 PM
>>To: M Stauffer (V); Luis Ibanez
>>Cc: ITK
>>Subject: Re: [Insight-developers] ImageRegion bounds caching
>>
>>2 things:
>>
>>1. Turning on numerical exceptions would have caught this.
>>2. I don't know if there's a safe way to test for NaN and inf
>>values with
>>numeric exceptions turned on. If you're testing for them, it
>>could make it
>>so nothing would work with floating point exceptions turned on.
>>
>>On 3/1/11 2:27 PM, "M Stauffer (V)" <mstauff at verizon.net> wrote:
>>>I will however add to ImageRegionTest to make sure that IsInside(
>>>ContinuousIndex ) returns false for NaN and Inf values, as I did
>>>recently for ImageFunction::IsInsideBuffer. Currently
>>>ImageRegion::IsInside ContinousIndex ) does return false for NaN, but
>>>only because NaN is cast to integer which yields a massive negative
>>>number that is out of bounds. The test will make sure this
>>works on all
>>>platforms and remains this way in the future.
>>
>>
>>
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>
>ITK_USE_FLOATINGPOINTEXCEPTIONS



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