Enforce the positivity of standard errors in the maximum likelihood
estimations. Otherwise some stderr are estimated negative, and the Bayesian
estimation fail because the initial value is out of the bounds of the prior
shape.
The change implemented in 21a8a5794a broke the
testsuite and was incomplete.
– new option “overwrite” to provide the old behaviour (used to fix the testsuite);
– when concatenating several “estimated_params” block, the preprocessor now
checks that paramateres are not declared twice across blocks.
This optimizer seems more robust accross different hardware (with other
optimizers, the algorithm does not converge to a local maximum, e.g. on the
runner "lupi").