I am fitting a semiparametric generalized linear mixed effect model with a DP
prior on the random effects and I use a truncated approximation of the DP. If
I add a prior on the mass parameter of the DP, after several iterations I
obtain this error message:
Errore: RUNTIME ERROR:
Singularity in likelihood found by Slicer
What does it mean? Where is the problem?
Thank you for your help,
I've received the same error with one of my more complex models when running
JAGS 2.2.0 64-bit via R on Windows. While I can't explain the error, I do know
that my particular model worked fined with JAGS 2.1.0.
The problem is that some distributions have unbounded probability density
functions ( e.g. Dirichlet, Beta, Gamma when the relevant shape parameter is
less than 1). If the slice sampler finds itself at a point where the current
log-density is infinite then it cannot move away from it. But it is necessary
to have a finite probability of moving away from the current state at all
times in order to satisfy the regularity conditions on which the whole MCMC
Previously the slice sampler did not issue a warning but simply stayed where
it was. Now it stops with an error message. Am I being too cautious? I don't
know. In practice it seems that the sampler was able to move away from the
singularity eventually, but I'm a lot more worried about JAGS appearing to
work and giving the wrong answer than I am about some models not being able to
run. You can usually work around the problem by strengthening the prior or
bounding the distribution away from the boundary where the singularity lies.
The model compiles, initializes correctly, an error occurs during updating,
but the current state of the model doesn't dump to a ﬁle named jags.dump1.R.
I would like to know which unbounded prior cause this problem.
How can I obtain the current state of the chain?
I have the same problem.
I am using a Dependent Dirichlet Process and I put an inverse-gamma prior on
the mass parameter.
After some iterations JAGS stops with the error:
Singularity in likelihood found by Slicer.
I don't understand where is exactly the problem. How can I obtain the state of
the chain when JAGS stops?
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