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Stopping's attributes ID: StoppingMeta

Usual instances of AbstractStopping contains a StoppingMeta <: AbstractStoppingMeta (stp.meta), which controls the various tolerances and thresholds used by the functions start! and stop!.

  • atol :: Number = 1.0e-6
  • rtol :: Number = 1.0e-15
  • optimality0 :: Number = 1.0
  • tol_check :: Function = (atol :: Number, rtol :: Number, opt0 :: Number) -> max(atol,rtol*opt0)
  • tol_check_neg :: Function = (atol :: Number, rtol :: Number, opt0 :: Number) -> - tol_check(atol,rtol,opt0)
  • optimality_check :: Function = (a,b) -> Inf
  • recomp_tol :: Bool = true
  • unbounded_threshold :: Number = 1.0e50, #typemax(Float64)
  • unbounded_x :: Number = 1.0e50
  • max_f :: Int = typemax(Int)
  • max_cntrs :: Dict{Symbol,Int} = Dict{Symbol,Int64}()
  • max_eval :: Int = 20000
  • max_iter :: Int = 5000
  • max_time :: Float64 = 300.0
  • start_time :: Float64 = NaN
  • meta_user_struct :: Any = nothing
  • user_check_func! :: Function = (stp :: AbstractStopping, start :: Bool) -> nothing

The default constructor for the meta uses above values, and they can all be modified using keywords

meta = StoppingMeta(rtol = 0.0) #will set `rtol` as 0.0.

StoppingMeta also contains the various status related to the checks:

OK_check(meta) #returns true if one of the check is true.

FAQ: Are there Type constraints when initializing a StoppingMeta?

An StoppingMeta{TolType, CheckType, MUS, IntType} is actually a paramtric type:

checktype(meta) #CheckType: return type of `tol_check` and `tol_check_neg` 
toltype(meta) #TolType: type of the tolerances
metausertype(meta) #MUS: type of the user-defined structure
inttype(meta) #IntType: type of integer tolerances

FAQ: What is user_check_func!?

This is a callback function called in the execution of the function stop! or start!. This function takes two input stp <: AbstractStopping and a boolean set as true if called from start! and false if called from stop!. To eventually returns a stopping status, the function has to update stp.meta.stopbyuser.

For instance, if one want to stop when $\log(x) < 1$ in stop!:

function test(stp, start)
  stp.meta.stopbyuser = !start && (log(stp.current_state.x) < 1)
end
user_check_func! = test

The exclamation mark (!) is a naming convention used when the function modifies input.