Cobaya minimizer question

 Posts: 17
 Joined: October 05 2021
 Affiliation: UCI
Cobaya minimizer question
I want to run minimization over the calculated chains using mcmc with cobaya and I don't know where you I write the path of the chains so that the program can use them to do a more precise minimazation? Thanks!

 Posts: 1852
 Joined: September 23 2004
 Affiliation: University of Sussex
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Re: Cobaya minimizer question
You need to do a minimization run to find a minimum, you can't find a global minimum from chains since in high dimensions there are almost no samples near the posterior peak.

 Posts: 17
 Joined: October 05 2021
 Affiliation: UCI
Re: Cobaya minimizer question
Thanks for your answer!
I am running nested models, for example, LCDM and the LCDM + w free, therefore, I'm expecting a better fit for the model that has more freedom (in this case LCDM+w. Nevertheless, when I run minimizer over this two models, I get a smaller minuslogpost (in absolute magnitude) for the LCDM than for the LCDM + w free, which is mathematically inconsistent. I have ran the full chains since I thought it was necessary in order to run the minimizer.
How I set up the minimizer run is by changing the last part in the .yaml file (instead of mcmc sampler):
Is this the way to proceed or am I doing something wrong? How should one set this run?
Thanks in advanced!
I am running nested models, for example, LCDM and the LCDM + w free, therefore, I'm expecting a better fit for the model that has more freedom (in this case LCDM+w. Nevertheless, when I run minimizer over this two models, I get a smaller minuslogpost (in absolute magnitude) for the LCDM than for the LCDM + w free, which is mathematically inconsistent. I have ran the full chains since I thought it was necessary in order to run the minimizer.
How I set up the minimizer run is by changing the last part in the .yaml file (instead of mcmc sampler):
Code: Select all
sampler:
minimize:
method: bobyqa
ignore_prior: False
max_evals: 1e6d
best_of: 2
confidence_for_unbounded: 0.9999995
Thanks in advanced!

 Posts: 1852
 Joined: September 23 2004
 Affiliation: University of Sussex
 Contact:
Re: Cobaya minimizer question
Looks OK. You can make use of your chains by setting the minimizer "covmat" to the covariance matrix from your chains. The minimizer may work much better with a sensible covmat.