[ITK-dev] MatrixOffsetTransformBase::GetFixedParameters not ThreadSafe -- regression test?

[Bradley Lowekamp]

Kent,

Mutable member are evil.

Would it be possible to have the m_Center and the m_FixedArray point to the same block of data?

Brad

On Oct 24, 2014, at 12:59 PM, Williams, Norman K <norman-k-williams at uiowa.edu> wrote:

> The problem is worse than I thought.
> 
> CompositeTransform::GetFixedParameters() dynamically resizes the FixedParameters array, and then does a bunch of std::copy to copy fixed parameters out of its list of sub-transforms.
> 
> The only way to make that thread safe is to use a Mutex lock to guard where it changes the member variable.
> 
> From: <Williams>, Mushly McMushmaster <norman-k-williams at uiowa.edu>
> Date: Friday, October 24, 2014 at 11:45 AM
> To: ITK <insight-developers at itk.org>
> Subject: [ITK-dev] MatrixOffsetTransformBase::GetFixedParameters not ThreadSafe -- regression test?
> 
> I was going to address this bug that I just logged:
> 
> https://issues.itk.org/jira/browse/ITK-3324
> 
> Basically, if GetFixedParameters is called from multiple threads, it introduces a race to resize the internal fixed parameter array.
> 
> This was never  a problem before Hans Johnson’s recent patch to propagate fixed parameters int Transform::GetInverse() methods.  He added:
> 
> inverse->SetFixedParameters(this->GetFixedParameters());
> 
> which makes perfect sense.
> 
> I have a decent idea of how to make this better:  Set the fixed parameters’ size in the constructor for MatrixOffsetTransformBase, and set the fixed parameters in SetCenter.  I will review the other instances of GetFixedParameters and GetParameters to see if they’re similarly thread-unsafe.
> 
> But how do you write a regression test for this?
> 
> 
> 
> 
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