Fix IB patch vel/angular_vel/angles broadcast inside wrong loop

[sbryngelson]

Summary

Severity: HIGH — IB patch vel/angular_vel/angles broadcast in wrong loop with wrong bounds.

File: src/pre_process/m_mpi_proxy.fpp, lines 79-81

The patch_ib(i)%vel, patch_ib(i)%angular_vel, and patch_ib(i)%angles broadcasts are inside the do i = 1, num_bc_patches_max loop, but they reference patch_ib which should be iterated up to num_patches_max (where all other patch_ib fields are broadcast).

Before

do i = 1, num_bc_patches_max        ! BC patches loop
    ! patch_bc broadcasts... (correct)
    call MPI_BCAST(patch_ib(i)%vel, ...)          ! WRONG loop!
    call MPI_BCAST(patch_ib(i)%angular_vel, ...)  ! WRONG loop!
    call MPI_BCAST(patch_ib(i)%angles, ...)       ! WRONG loop!
end do
do i = 1, num_patches_max           ! patches loop
    ! other patch_ib broadcasts... (correct loop, missing vel/angular_vel/angles)
end do

After

Moved the vel/angular_vel/angles broadcasts into the num_patches_max loop alongside the other patch_ib fields.

Why this went undetected

If num_bc_patches_max >= num_patches_max, all IB patches would still get broadcast (with some extra unnecessary iterations). Only fails when there are more IB patches than BC patches.

Test plan

• Run multi-rank simulation with immersed boundaries
• Verify IB patch velocities/angles are consistent across ranks

🤖 Generated with Claude Code

Fixes #1208

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[codeant-ai]

Nitpicks 🔍

🔒 No security issues identified

⚡ Recommended areas for review Consistency of broadcast loop The motion fields were moved from the boundary-patch loop to the main patch loop — this is likely correct. Still verify that num_patches_max covers all patches that need motion data and that no IB patches exist only under num_bc_patches_max such that they might be missed. Hard-coded count The new MPI_BCAST for vel, angular_vel and angles uses a fixed count of 3. If any of these arrays are not guaranteed to be length 3 for all patches (e.g. different dimensionality or future changes), the broadcast will be incorrect. Prefer using the actual array size (size(...)) so the count always matches the local variable storage. Broadcast granularity The code issues many small MPI_BCAST calls (per-field, per-patch). For large numbers of patches this can create significant MPI overhead and hurt scalability. Consider packing related IB fields into a single contiguous buffer (or using derived MPI types) and broadcasting once per patch to reduce message count.

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[Copilot]

Pull request overview

Moves the patch_ib broadcasts for vel, angular_vel, and angles to the correct loop so they align with the other patch_ib fields and are broadcast for the proper num_patches_max range.

Changes:

• Removed patch_ib vector broadcasts from the patch_bc loop (num_bc_patches_max context).
• Added patch_ib vector broadcasts alongside the other patch_ib broadcasts (num_patches_max context).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.05%. Comparing base (84c46e0) to head (7c10279).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1188   +/-   ##
=======================================
  Coverage   44.05%   44.05%           
=======================================
  Files          70       70           
  Lines       20498    20498           
  Branches     1990     1990           
=======================================
  Hits         9030     9030           
  Misses      10329    10329           
  Partials     1139     1139           

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[sbryngelson]

Superseded by #1241 (batched low-risk fixes)