Solver.poisson support pre-integrated vfuncs

[magnesium2400]

• Solver.poisson always multiplies the input vfunc h by self.mass to generate an integrated map
• This creates difficulties when solving for different maps, where some are integrated, and some are not: a new Solver object has to be created and its mass set to the identity
• It is easier to create a flag where the user can specify if the map is already integrated or not. This is what I have done here.
• This also simplifies the code in diffgeo.compute_geodesic_f etc.
• The default behaviour is preserved
• The figures in Test_TriaMesh_Geodesics.ipynb still look good when vf = fem.poisson(Bi * divx) is replaced by vf = fem.poisson(divx, integrate=False)

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 50.01%. Comparing base (dcacc4a) to head (6002763).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
lapy/diffgeo.py	83.33%	1 Missing ⚠️

Additional details and impacted files

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##             main     #115      +/-   ##
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- Coverage   50.04%   50.01%   -0.04%     
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  Files          15       15              
  Lines        3153     3151       -2     
  Branches      414      415       +1     
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- Hits         1578     1576       -2     
  Misses       1426     1426              
  Partials      149      149              

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[Copilot]

Pull request overview

This PR adds an option to Solver.poisson to skip mass-matrix integration when the RHS is already pre-integrated, and updates differential-geometry helpers to use that option instead of mutating Solver.mass.

Changes:

• Add integrate: bool = True to Solver.poisson to optionally bypass B*h integration.
• Update diffgeo.compute_geodesic_f, tria_compute_geodesic_f, and tria_compute_rotated_f to call poisson(..., integrate=False) instead of replacing fem.mass with the identity.
• Document the new flag in the poisson docstring.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
lapy/solver.py	Introduces integrate flag and conditional mass-matrix application when building the RHS.
lapy/diffgeo.py	Switches geodesic/rotated-function routines to use integrate=False rather than altering solver state.

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[m-reuter]

Hi @magnesium2400 thanks for this PR. I like to integrate it, but first the comments above need to be resolved. Fixing the doc-string to numpy format should also fix the doc build CI error.

[magnesium2400]

ok thanks @m-reuter , i will only have time in a few weeks but will do it then. and sorry, I couldnt find the tests anywhere (I could only see the notebooks) -- where/how should i write the tests (can I use pytest)? cheers.

[m-reuter]

Hi, tests are under lapy/utils/tests ( we will move them at some point into the project root, but currently you can add things there, if you find a similar tests already, if not, don't worry too much about the test). The other comments are more important.

[magnesium2400]

thanks @m-reuter , i think i did all the changes that were brought up earlier. they were just small changes to the comments/docstrings. I added a simple test.

[m-reuter]

Thanks for your contribution!