st: ml tolerance

["Gregory, Christian" <cgregory@ers.usda.gov>]

Hi,

I'm using ml to estimate a model.

1. I'm using <showtolerance> option: the output reports "ptol" and
"vtol." Do these refer to difference in likelihood or parameter
estimates? I cannot find reference to them in any of the manuals.

2. In computing the scaled gradient (g()*H*g()'), how does Stata compute
the Hessian? I'm using an lf1 type estimator: does it compute the
Hessian numerically from the gradients that I have written? Or does it
compute them numerically from numeric gradients that it calculates?

Thanks,
Christian



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