[CosmoMC/Planck likelihood] Precision
[CosmoMC/Planck likelihood] Precision
Dear all,
Does anyone know how precise the Planck likelihood values that we get out of CosmoMC are? When looking at analysis with the likelihood values, it's really important to know what the actual precision is so we don't get dominated by noise in the numerical analysis. Does anyone know how accurate the likelihood values are (i.e. of the 6466.xxxxxx for the best fit value I have for a given parameter set, what is the number of d.p. one can go to before this becomes noise dominated)?
Thanks in advance for your help
Luke
Does anyone know how precise the Planck likelihood values that we get out of CosmoMC are? When looking at analysis with the likelihood values, it's really important to know what the actual precision is so we don't get dominated by noise in the numerical analysis. Does anyone know how accurate the likelihood values are (i.e. of the 6466.xxxxxx for the best fit value I have for a given parameter set, what is the number of d.p. one can go to before this becomes noise dominated)?
Thanks in advance for your help
Luke

 Posts: 1472
 Joined: September 23 2004
 Affiliation: University of Sussex
 Contact:
Re: [CosmoMC/Planck likelihood] Precision
The noise is the likelihood itself is small. However there will be numerical noise in the parameters of the bestfit point, which can be O(1).
Re: [CosmoMC/Planck likelihood] Precision
Thanks Antony, but I just wanted to ask: what do you mean when you say 'O(1)' ??

 Posts: 1472
 Joined: September 23 2004
 Affiliation: University of Sussex
 Contact:
Re: [CosmoMC/Planck likelihood] Precision
I mean chi^2 can move around by O(1) depending on where exactly the minimizer ends up (though usually stable to somewhat below \pm 1).