CosmoMC: special prior

[Zhuangfei Wang]

Hello:
I have a question about how to set some special prior in CosmoMC. For example, I'd like to prescribe two input parameters to always obey such relation: para1>para2, so that the value pairs that don't satisfy this prior will be filtered out, even if a large flat range is preset for both parameters. Is it possible to implement it? I know about flat priors or setting limits in .ini for single-end parameters, but I am not sure how to set more complicated prior as described above. Thanks a lot.

[Antony Lewis]

See
https://cobaya.readthedocs.io/en/latest/params_prior.html#multidimensional-priors

[Zhuangfei Wang]

Thanks for your reply. It seems to be easy in Cobaya by checking the docs. Just wondering if it is doable in CosmoMC?

[Antony Lewis]

Yes, you'll have to change the code calculating the prior and recompile (search the code for prior).