Tearing.Dispersion - Scale the polish's finite-difference step to |Q|
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Assessment
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Newbie friendliness
- 54/100
- Issue type
- Bug
- Clarity
- Mostly clear
- Activity status
- Active
- Tech stack
- julia
- Domain
- performance
Research direction
Find _polish_root and inspect how its finite-difference step h is used to compute the Jacobian near small trust radii and large |Q|. Run the harness before and after any proposed step scaling, then compare and report changes in accepted roots.
Written by the indexing model from the issue text.
Description
_polish_root uses h = max(1e-3 R, eps(Float64)), where R is the trust radius. The step does not scale with |Q|.
- When R is small (near-coincident intersections),
fx - fkloses digits to cancellation. - If h ever falls below about eps·|Q|,
Q + h == Q, the Jacobian determinant is zero, and the polish silently does nothing.
Proposal: h = clamp(1e-3 R, sqrt(eps)·max(|Q|, 1), R/2), or an equivalent relative step. This changes the polish numerics slightly, so it needs a harness run, and any change in accepted roots should be reported.
- Dominant language
- Julia
- Stars
- 11
- Forks
- 7
- Avg merge
- 4d 3h
- Merged PRs (30d)
- 70
Getting set up
- No Dockerfile or Docker Compose file
- Has a pull request template
- No contributing guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
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