Is fit validity or minimizer status more important?

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Hi,

They are both relevant. The valid flag tells you have reached a minimum, but the minimiser status returns (for some of the minimiser such as Minuit) more information.
For example using Minuit2 you have as status:

  • status = 1 : Covariance was made pos defined
  • status = 2 : Hesse is invalid
  • status = 3 : Edm is above max
  • status = 4 : Reached call limit
  • status = 5 : Covariance is not positive defined

For status=0 or 1 the fitted status will be valid, while in the other cases (status=2,3,4,5) it will not be.

Lorenzo

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