InnerLayer.SLAYER - BUGFIX - Fail clearly when the minor-radius derivative at a rational surface is unusable

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
48/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
julia
Domain
backend

Research direction

Start with src/InnerLayer/SLAYER/LayerInputs.jl and LayerParameters.jl, where the issue says build_slayer_inputs computes the surface values; trace how each surface’s r_s and da/dψ are obtained. Check both values for finite positivity across every dc_type, and consider the requested migration note for this behavior change. Done means invalid values produce one error naming the surface index and ψ, with tests covering the listed cases.

Written by the indexing model from the issue text.

Description

Summary

build_slayer_inputs converts the outer Δ′ to the r_s reference with K = r_s / (da/dψ). When da/dψ at a rational surface is not a usable positive number, what happens depends on how it is unusable, and none of the outcomes names the real problem.

What happens today

From reading src/InnerLayer/SLAYER/LayerInputs.jl and LayerParameters.jl on develop; not reproduced with a run.

da/dψ at the surface outcome
zero r_based_shear throws "da/dψ must be non-zero"
NaN or Inf, with a critical-Δ model on and D_R ≠ 0 the W_d loop never converges and throws "Wd iteration failed to converge"
NaN, dc_type = "none" NaN layer parameters pass through with only the warning below
finite and negative a warning (at most three per session), K = 1, Δ′ left unconverted, and the run returns a plausible-looking root from mismatched references

For nested flux surfaces da/dψ is positive, so any of these means something upstream is wrong (spline noise at the extreme edge, or an unsuitable radial label). The last row is the one that can produce a wrong number without stopping.

A related gap: under rs_method = :volume the minor radius itself can come out as zero while da/dψ stays positive. Then K = 0, the derived toroidal factor is zero, and the toroidal critical Δ is switched off without a message.

Proposal

Check the pair (r_s, da/dψ) once, right where they are computed for each surface, and raise an error that names the surface index and ψ when either is not a finite positive number, for every dc_type. That replaces three different symptoms with one message.

The cost is that one bad surface stops a SLAYER run that today finishes with a warning, so this is a behaviour change and needs a migration note.

Dominant language
Julia
Stars
11
Forks
7
Avg merge
4d 3h
Merged PRs (30d)
70

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