[rocBLAS] Refactor memory management in host_alloc.cpp

[tony-davis]

Summary

Improved memory management in host_alloc.cpp by refactoring the deallocation logic for better efficiency and adding diagnostic warnings for untracked pointer frees.

Changes

1. Refactored free_ptr_use() to use iterator-based access (reduces redundant map lookups)
2. Added warning for freeing untracked pointers (helps detect potential memory corruption issues)

Motivation

The current implementation of free_ptr_use() in host_alloc.cpp had two issues:

1. Performance: Redundant map lookups when deallocating tracked memory
2. Correctness: Using operator[] on a map can unintentionally insert entries for non-existent keys
3. Diagnostics: Silent failures when attempting to free untracked pointers made debugging difficult

This PR addresses all three issues by refactoring the lookup logic and adding diagnostic warnings.

Technical Details

File: projects/rocblas/clients/common/host_alloc.cpp

Change 1: Iterator-based memory deallocation

Before:

if(ptr && mem_allocated[ptr]) {           // Lookup #1 (may insert!)
    mem_used -= mem_allocated[ptr];       // Lookup #2
    mem_allocated.erase(ptr);             // Lookup #3
}

After:

auto it = mem_allocated.find(ptr);        // Single lookup
if(ptr && it != mem_allocated.end()) {
    mem_used -= it->second;               // Use cached iterator
    mem_allocated.erase(it);              // Use cached iterator
}

Benefits:

• Reduces map lookups from 3 to 1
• Prevents unintended map insertions via operator[]
• More efficient memory tracking

Change 2: Diagnostic warning for untracked pointers

Added:

else if(ptr && call_free)
{
    rocblas_cerr << "Warning: Freeing untracked pointer " << ptr
                 << " - untracked memory released (potential double-free or memory corruption)"
                 << std::endl;
}

Benefits:

• Helps detect double-free bugs
• Identifies potential memory corruption issues
• Provides actionable diagnostic information during testing

Test Plan

• Built rocBLAS with no compilation errors
• Existing client test suite exercises memory allocation/deallocation paths
• No functional behavior changes to normal operation
• Warning messages help identify issues during debugging

Test Result

• All existing tests continue to pass
• Memory tracking functionality unchanged
• Warning properly triggers for untracked pointer frees
• No behavioral differences for correctly tracked memory

Submission Checklist

• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

[Copilot]

Pull request overview

This PR refactors the memory deallocation logic in free_ptr_use() to use iterator-based map access, improving both efficiency and correctness. The change eliminates redundant map lookups and prevents unintended insertions that could occur with operator[].

Key Changes:

• Replaced three sequential map lookups with a single find() call using an iterator
• Used the cached iterator for subsequent operations (accessing size and erasing entry)
• Eliminated risk of unintended map insertions when checking for pointer existence

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3672      +/-   ##
===========================================
- Coverage    49.69%   46.04%   -3.65%     
===========================================
  Files          134      365     +231     
  Lines        33491    51594   +18103     
  Branches      4399     5964    +1565     
===========================================
+ Hits         16641    23752    +7111     
- Misses       15607    24359    +8752     
- Partials      1243     3483    +2240     

Flag	Coverage Δ
hipFFT	?
rocBLAS	46.04% <ø> (?)
rocFFT	?

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[TorreZuk]

I approve but my suggestions I usually want considered to be made before merge :-)
My style is I only don't approve if I think the merge would cause trouble as is.

[TorreZuk]

Looks like you have to run clang format again, otherwise only baseline fails.