uq_postProcessInversion: Problem: burnIn fraction does not lead to consistent number of posterior sample points

Dear UQWorld community,

I encountered a similar issue as mentioned in the Feature request (already closed), this time for the fraction instead of the integer value.

In the manual for Bayesian inversion on page 55, it says for ‘burnIn’:

Specifies the fraction of sample points that are discarded as burn-in

However, it seems to me that the burn-in fraction times the chosen number of steps is the first step to be used in the post-processed sample. Is that correct?

Concrete example: In my code, I use 400 steps and 100 chains and the default burn-in of 0.5. When I call

PostSample2D = reshape(permute(myBayesianAnalysis.Results.PostProc.PostSample, [2 1 3]), size(PostSample3D, 2), []);

as suggested in Looking for documentation/example of using UQLab results of Bayesian inference for forward UQ or further Bayesian inference to access the posterior sample, I obtain 2x20,100 posterior sample. But for a default burn-in of 0.5, you would expect a 2x20,000 posterior sample.

So, is there a msimatch between the implementation and the documentation?

I am using UQLabCore, version 1.3.0. In case, the issue has already been solved in the new version, I apologize for bringing the topic up again.

Thanks in advance for your clarification.

Best regards