Remove tsk_bug_assertion in pair_coalescence_rates triggered by fp error

[nspope]

Apologies for dropping a bug fix immediately after a release (fixes #3035).

This removes an assertion from the C library that can be spuriously triggered by a floating point comparison against 1 (which should only happen in the edge case where a single time window contains all the coalescence events).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.07%. Comparing base (84ebb0b) to head (39593ec).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3038      +/-   ##
==========================================
- Coverage   89.85%   87.07%   -2.78%     
==========================================
  Files          29       11      -18     
  Lines       32128    24666    -7462     
  Branches     5763     4556    -1207     
==========================================
- Hits        28868    21478    -7390     
+ Misses       1859     1824      -35     
+ Partials     1401     1364      -37     

Flag	Coverage Δ
c-tests	86.69% <ø> (ø)
lwt-tests	80.78% <ø> (ø)
python-c-tests	89.05% <ø> (ø)
python-tests	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
c/tskit/trees.c	90.68% <ø> (ø)

... and 18 files with indirect coverage changes

[jeromekelleher]

Can we get a test case provoking the old assert?

[nspope]

I added a test that would hit the assert on main. There's a check for the failure condition (roundoff error) on the python side.

[jeromekelleher]

Nice - I think it's important to capture odd corner cases in the test suite as they tend to recur...

[nspope]

I agree! I think this is ready to go in, then?

[nspope]

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I've logged out/in to mergify again but not sure if it'll pick up on that

[benjeffery]

@Mergifyio rebase

[mergify]

rebase

✅ Branch has been successfully rebased

[benjeffery]

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I've logged out/in to mergify again but not sure if it'll pick up on that

I'm not sure why but recently it hasn't been merging PRs from accounts not on a fixed list. I've manual merged.