fix(lmp): clear DPLR PPPM force cache

[Yi-FanLi]

Summary

• add a small helper to resize and zero the DPLR PPPM fele cache
• clear fele before returning from PPPMDPLR::compute when qsqsum == 0
• reuse the same helper in init and fieldforce paths

This addresses #5647 as a defensive consistency fix. In normal DeePMD DPLR usage, atom charges are fixed and are not changed from nonzero to all-zero during a run, so this stale-cache path should not be triggered by standard DeePMD workflows. It would only matter for unusual external charge mutation or reinitialization paths where qsqsum is refreshed to zero after a previous nonzero-charge PPPM/DPLR step.

Tests

• git diff --check
• /tmp/deepmd-check-venv/bin/ruff check .
• /tmp/deepmd-check-venv/bin/ruff format --check .

Summary by CodeRabbit

• Bug Fixes

  • Improved consistency in per-atom field/force handling by clearing the accumulator before early exits and during setup.
  • Reduced the chance of stale values carrying over between calculations.

• Refactor

  • Consolidated repeated zeroing and resizing steps into a shared internal routine, simplifying the calculation flow and making the code easier to maintain.

[coderabbitai]

📝 Walkthrough

Walkthrough

Introduces a private clear_fele() method in PPPMDPLR that resizes and zero-fills the fele accumulator. Replaces duplicated inline resize/zero logic in init(), fieldforce_ik(), and fieldforce_ad() with calls to this helper, and adds a call to it in compute()'s early-return path when qsqsum == 0.0.

Changes

fele Clearing Refactor

Layer / File(s)	Summary
clear_fele helper declaration and definition source/lmp/pppm_dplr.h, source/lmp/pppm_dplr.cpp	Adds a private clear_fele() declaration to the class and implements it to resize fele to atom->nlocal * 3 and zero-fill it.
Wiring clear_fele into init, compute, and fieldforce paths source/lmp/pppm_dplr.cpp	Replaces inline resize/zero logic with clear_fele() calls in init(), fieldforce_ik(), and fieldforce_ad(), and adds a clear_fele() call in compute()'s qsqsum == 0.0 early-return path.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Compute as PPPMDPLR::compute
  participant Init as PPPMDPLR::init
  participant FieldforceIK as PPPMDPLR::fieldforce_ik
  participant FieldforceAD as PPPMDPLR::fieldforce_ad
  participant ClearFele as PPPMDPLR::clear_fele

  Init->>ClearFele: reset fele buffer
  Compute->>ClearFele: reset fele on qsqsum == 0.0
  FieldforceIK->>ClearFele: reset fele buffer
  FieldforceAD->>ClearFele: reset fele buffer
  ClearFele->>ClearFele: resize fele to nlocal*3 and fill with 0.0

Loading

Possibly related issues

• [Code scan] Clear pppm/dplr electric forces when charges vanish #5647: Implements the same pppm/dplr stale-fele fix described in the issue, including clearing fele on the qsqsum == 0.0 early return.

Suggested reviewers: njzjz

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: clearing the DPLR PPPM force cache.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

source/lmp/pppm_dplr.cpp (1)

51-55: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Optional: use assign instead of resize + fill.

fele.assign(static_cast<size_t>(nlocal) * 3, 0.0); achieves the same result in one call.

♻️ Optional simplification

 void PPPMDPLR::clear_fele() {
   int nlocal = atom->nlocal;
-  fele.resize(static_cast<size_t>(nlocal) * 3);
-  fill(fele.begin(), fele.end(), 0.0);
+  fele.assign(static_cast<size_t>(nlocal) * 3, 0.0);
 }

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@source/lmp/pppm_dplr.cpp` around lines 51 - 55, The clear_fele() method in
PPPMDPLR currently resizes fele and then fills it with zeros in two steps;
simplify this by using fele.assign(static_cast<size_t>(nlocal) * 3, 0.0) to
initialize the buffer in one call. Keep the behavior the same and update only
the fele initialization logic inside PPPMDPLR::clear_fele().

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@source/lmp/pppm_dplr.cpp`:
- Around line 51-55: The clear_fele() method in PPPMDPLR currently resizes fele
and then fills it with zeros in two steps; simplify this by using
fele.assign(static_cast<size_t>(nlocal) * 3, 0.0) to initialize the buffer in
one call. Keep the behavior the same and update only the fele initialization
logic inside PPPMDPLR::clear_fele().

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 585df065-3b96-4ee5-ba19-0facf93c76a9

📥 Commits

Reviewing files that changed from the base of the PR and between 3d73c67 and 0a487fc.

📒 Files selected for processing (2)

• source/lmp/pppm_dplr.cpp
• source/lmp/pppm_dplr.h

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.22%. Comparing base (3d73c67) to head (0a487fc).

Files with missing lines	Patch %	Lines
source/lmp/pppm_dplr.cpp	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5744      +/-   ##
==========================================
- Coverage   81.36%   81.22%   -0.14%     
==========================================
  Files         991      991              
  Lines      111198   111200       +2     
  Branches     4235     4234       -1     
==========================================
- Hits        90474    90324     -150     
- Misses      19199    19349     +150     
- Partials     1525     1527       +2     

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