fix ibm benchmark on frontier + amd

[anandrdbz]

User description

Description

Simple bug fix that was introduced in a recent PR; AMD compilers don't like update device when the array bounds are 1:0.

Fixes #(issue)

Type of change

• Bug fix
• New feature
• Refactor
• Documentation
• Other: describe

Testing

How did you test your changes?

Checklist

• I added or updated tests for new behavior
• I updated documentation if user-facing behavior changed

See the developer guide for full coding standards.

GPU changes (expand if you modified src/simulation/)

• GPU results match CPU results
• Tested on NVIDIA GPU or AMD GPU

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CodeAnt-AI Description

Prevent GPU update when there are zero ghost points to avoid AMD failure

What Changed

• The subroutine returns immediately when the ghost-point count is less than 1, so no GPU update or kernel launch is attempted for empty arrays
• Removes the condition that caused AMD compilers or runtimes to reject an update with an array slice of bounds 1:0
• All other behavior for non-empty ghost-point arrays is unchanged

Impact

✅ Runs IBM benchmark on Frontier without AMD compile/runtime error
✅ Fewer GPU launch failures when arrays are empty
✅ Stable execution when no ghost points are present

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Summary by CodeRabbit

• Bug Fixes
  • Improved performance by preventing unnecessary processing when no items require computation.

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[coderabbitai]

📝 Walkthrough

Walkthrough

An early exit condition is added to the s_apply_levelset function that immediately returns when the number of ghost points is less than 1, skipping GPU updates and per-ghost-point processing.

Changes

Cohort / File(s)	Summary
Early Exit Optimization src/simulation/m_compute_levelset.fpp	Added guard clause in s_apply_levelset to skip processing when num_gps < 1, preventing unnecessary GPU updates and ghost-point iterations.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~5 minutes

Suggested labels

Review effort 2/5, size:XS

Poem

🐰 An early exit, swift and clean,
When zero ghosts dance on the scene,
No GPU load, no loops to spin,
Just skip and return—optimization wins! ✨

🚥 Pre-merge checks | ✅ 1 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The pull request description includes most required sections but lacks critical testing details and GPU verification confirmations despite modifying GPU code.	Complete the Testing section with specific test procedures, and confirm GPU parity checks and AMD GPU testing in the GPU changes section by checking the appropriate boxes.
Title check	❓ Inconclusive	The title 'fix ibm benchmark on frontier + amd' is somewhat vague and lacks specificity about the actual bug being fixed.	Clarify the title to mention the core issue (e.g., 'Prevent GPU update when ghost-point array bounds are empty') for better clarity about the specific bug being addressed.

✅ Passed checks (1 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[codeant-ai]

Nitpicks 🔍

🔒 No security issues identified

⚡ Recommended areas for review GPU update guarding The root cause is a GPU update with an array slice gps(1:num_gps) when num_gps==0. A safer pattern is to guard individual GPU directives/launches with a conditional (so only GPU calls are skipped) rather than returning from the entire subroutine. This keeps CPU-side behaviors intact if the routine evolves. Early-return semantics The added early return (when there are no ghost points) prevents any further execution of the subroutine. This is likely intentional to avoid launching GPU updates with an empty slice, but it also skips every subsequent statement (including non-GPU logic that might be added later). Confirm that skipping all remaining code for num_gps <= 0 is correct for all current and future callers.

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CodeAnt AI finished reviewing your PR.

[cubic-dev-ai]

No issues found across 1 file

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 44.06%. Comparing base (c5493c1) to head (8095bb3).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/simulation/m_compute_levelset.fpp	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1159      +/-   ##
==========================================
- Coverage   44.07%   44.06%   -0.01%     
==========================================
  Files          70       70              
  Lines       20431    20431              
  Branches     1974     1975       +1     
==========================================
- Hits         9004     9003       -1     
  Misses      10291    10291              
- Partials     1136     1137       +1     

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