Running optimizer in parallel


i have a question regarding parallel optimization. The actual setup is more cpmplex. Therefore I try to simplify.

I have a reference image and multiple other images. I want to register the other images onto the reference image. The transformations are expected to be different (or weakly coupled).
Now I want to run each registration in parallel. This means I need to start multiple instances of optimizers (can be different optimizer types).

If I want to run the optimizers in parallel what would be the best approach?
The ITK offers three Mutlithreading options:
ThreadedGenerateData() -> This seems to be for single images to be splitted and processed .
itk::DomainThreader -> This seems to be the most feasable option.
itk::MultiThreader -> This might also work but with a lot of overhead code.

Have someone done something like this and could provide some insight?


Hello Gordian,

The best approach is to use itk::MultiThreaderBase::ParallelizeImageRegion in ITK 5 Beta for the most flexibility, performance, and programming ease. Use a different optimizer instance in each thread because they will need independent optimization states.


You could also use ParallelizeArray method, so each index of the array corresponds to one moving image.

You could create a vector of file names of moving images, and parallelize over that. And the procedure you might want to run in parallel takes a pointer to the fixed image and a filename string. And that procedure could be just one of the example registration methods.

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The ITK i am using is a modified version of ITK-4.13. As far as I can see the functions you mentioned are not available.
Is there a possible replacement or an easy way to introduce the MultiThreaderBase class to 4.13?

@dzenanz is right, and ParallelizeArray is better for this case.

These functions are only available in ITK 5 as a result of a major amount of internal refactoring.