Fix length tests

[Andrea-Havron-NOAA]

What is the feature?

• Fixes tests on length comps feature in FIMS

How have you implemented the solution?

• Adds new FIMS_dmultinom function that matches TMB and differs from R by NOT rounding to the nearest integer.
• Tests on length comps pass using the new function

Does the PR impact any other area of the project, maybe another repo?

• No

[github-actions]

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[kellijohnson-NOAA]

@Andrea-Havron-NOAA it might be helpful for @Bai-Li-NOAA's review if you rebase this to current dev. Looks like you are missing a few commits.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.71%. Comparing base (d5df270) to head (44fa66c).
Report is 1 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #739   +/-   ##
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  Coverage   68.71%   68.71%           
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  Files          44       44           
  Lines        4714     4714           
  Branches      197      197           
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  Hits         3239     3239           
  Misses       1428     1428           
  Partials       47       47           

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[Andrea-Havron-NOAA]

@Andrea-Havron-NOAA it might be helpful for @Bai-Li-NOAA's review if you rebase this to current dev. Looks like you are missing a few commits.

Thanks for the reminder @kellijohnson-NOAA! The branch has been rebased and is ready for review.

[Bai-Li-NOAA]

Non-blocking suggestion for this PR: Could we assign descriptive names to individual nll_components? That way, we won't have to guess that the first element corresponds to recruitment nll and the second to fleet1 index nll.

[kellijohnson-NOAA]

Great idea @Bai-Li-NOAA. I am just not entirely sure how to get this done because the elements present will change given the model structure. I am sure it is possible but we might have to think hard about how to do it correctly.

[Bai-Li-NOAA]

Big thanks to @Andrea-Havron-NOAA for identifying the difference in dmultinom() behavior between TMB and R. The fix to the tests looks great! I have a few minor edit suggestions and a potential non-blocking suggestion to refactor the interface in a separate PR. Let me know if you have any questions!