GetDist: mcsamples.py warning

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Dahee Lee
Posts: 16
Joined: April 16 2018
Affiliation: Kyungpook National University

GetDist: mcsamples.py warning

Post by Dahee Lee » December 31 2018

Hi.
When I use GetDist, I got this warning for my parameter V0.

[WARNING] [mcsamples.py:1149] auto bandwidth for V0 very small or failed (h=0.0003142188258111446,N_eff=7341.548063183055). Using fallback (h=0.0011550058718305806)

Result is here.
V0.png
V0.png (7.68 KiB) Viewed 588 times
What does that mean? And how can I solve this warning?

Sorry for my trivial questions.
Any help would be appreciated.

Antony Lewis
Posts: 1498
Joined: September 23 2004
Affiliation: University of Sussex
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Re: GetDist: mcsamples.py warning

Post by Antony Lewis » December 31 2018

It means the distribution is very spiky or not converged.
Have you set the parameter ranges for V0 correctly (e.g. thereby giving a fake spike across V0=0)?

Dahee Lee
Posts: 16
Joined: April 16 2018
Affiliation: Kyungpook National University

Re: GetDist: mcsamples.py warning

Post by Dahee Lee » January 28 2019

I set the range 0 to 100(because V0 is positive value), and there is no fake spike.
When the number of sample is small(below ~50000), there is no warning and compression.
But the sample number is larger, distribution(1d plot) is more compressed.
Result has worst e-value: R-1 = 0.00828, R-1 of V0 is 0.0233.

In addition, is it possible that position of peak is different from best-fit value in distribution(1d plot)?
In that, best-fit value is about 1.9 in GetdistGUI, but the peak is about 0.8.
Any help would be appreciated.

Antony Lewis
Posts: 1498
Joined: September 23 2004
Affiliation: University of Sussex
Contact:

Re: GetDist: mcsamples.py warning

Post by Antony Lewis » January 29 2019

What is the actual code used to make the plot? Are you setting the getdist ranges (not plot limits) explicitly? The global best fit does not have to agree with marginalized parameter peaks.

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