Modify optimal CFL calculation for PERK2 integrator and its docstring

[warisa-r]

According to @JoshuaLampert 's recommendation in #2008. I implemented these minor modifications to PairedExplicitRK2

• Now, the user can use one of the constructors:
  PairedExplicitRK2(num_stages, base_path_monomial_coeffs::AbstractString, dt_opt = nothing, bS = 1.0, cS = 0.5)
  without providing dt_opt unless the user wants to use StepsizeCallback without specifying the cfl_number by calling the function calculate_cfl(ode_algorithm::AbstractPairedExplicitRKSingle, ode)

• A note regarding what packages the user needs to import in order to use it is added to the integrator's docstring.

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[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 96.36%. Comparing base (1413120) to head (a5aa7c6).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ation/paired_explicit_runge_kutta/methods_PERK2.jl	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2123      +/-   ##
==========================================
- Coverage   96.36%   96.36%   -0.00%     
==========================================
  Files         477      477              
  Lines       37750    37752       +2     
==========================================
+ Hits        36376    36377       +1     
- Misses       1374     1375       +1     

Flag	Coverage Δ
unittests	96.36% <50.00%> (-<0.01%)	⬇️

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[JoshuaLampert]

Thanks! Can you please update the docstring to reflect the change? You also need to allow nothing for dt_opt, i.e. something like dt_opt::Union{Float64, Nothing} in the definition of the struct. GitHub doesn't let me to comment on these lines.

[warisa-r]

Thanks! Can you please update the docstring to reflect the change? You also need to allow nothing for dt_opt, i.e. something like dt_opt::Union{Float64, Nothing} in the definition of the struct. GitHub doesn't let me to comment on these lines.

Done! Thank you for your suggestion!

[JoshuaLampert]

Could you also note in the parameters list of the docstring that nothing is the default for dt_opt and shortly explain what this means (especially that using the CFL callback relies on dt_opt)?

[warisa-r]

Could you also note in the parameters list of the docstring that nothing is the default for dt_opt and shortly explain what this means (especially that using the CFL callback relies on dt_opt)?

Done! Thx for the suggestion :D

[DanielDoehring]

Thanks you two! I think this PR alone is not breaking, right?

[JoshuaLampert]

Yes, I agree. This should not be breaking. Everything that worked before, should also work with this PR.

[JoshuaLampert]

Thanks!