squll1peter

I added _clFinish();_ after every _clEnqueue*()_ commands in elastix source code to ensure that the queued command is executed on OpenCL device right after queuing, and run the program with...

I've forked a branch [here](https://github.com/squll1peter/elastix/), modified it and recompiled it against a freshly complied and installed ITK v5.0.1 to make sure that changes only applies to elastix source code. Before...

I'm afraid that I cannot fully reproduce your problem, the parameter file your provided is a CPU version rigid registration, and I'm not sure what kind of modification you've done...

This PR & comment summarized the reasoning and code elegantly, I really appreciate it!