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

[Williams, Norman K]

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<mailto:norman-k-williams at uiowa.edu>>
Date: Friday, October 24, 2014 at 11:45 AM
To: ITK <insight-developers at itk.org<mailto: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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