CosmoMC: variable CAMB running time

Use of Cobaya. camb, CLASS, cosmomc, compilers, etc.
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Paul Hunt
Posts: 3
Joined: May 16 2005
Affiliation: Oxford University

CosmoMC: variable CAMB running time

Post by Paul Hunt » February 28 2007

I'm using CosmoMC on a cluster with a modified version of CAMB that runs significantly faster in some regions of parameter space than in others. Will this produce misleading results from CosmoMC? Do I need to ensure that CAMB always takes the same length of time to run whatever the cosmological parameter values?

Thanks in advance,
Paul

Anze Slosar
Posts: 183
Joined: September 24 2004
Affiliation: Brookhaven National Laboratory
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CosmoMC: variable CAMB running time

Post by Anze Slosar » February 28 2007

Ah, very interesting thought.

It could potentially be a problem if you have one chain exploring "fast" part of parameter space and the other chain exploring "slow" one. However, it shouldn't matter if you ensure that each individual chain is well converged, which it should be, if you require small enough R-1. To be doubly sure, you should make separate plots from individual chains and see that they give compatible results...

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