CRITICAL: pcolormesh functionality completely broken - dimension validation failures

[krystophny]

CRITICAL BUG: pcolormesh Functionality Completely Broken

The pcolormesh_demo example fails with systematic dimension validation errors, indicating the pcolormesh functionality is completely broken.

Reproduction Steps

Execute pcolormesh Demo

fpm run --example pcolormesh_demo

Current Behavior (Broken)

[ERROR] pcolormesh: z dimensions must match x and y
[ERROR] pcolormesh: z dimensions must match x and y  
[ERROR] pcolormesh: z dimensions must match x and y

Multiple dimension validation errors occur, preventing any pcolormesh plots from being generated.

Expected Behavior

The pcolormesh demo should successfully create pseudocolor mesh plots showing different colormap and data visualization examples.

Impact Assessment

User-Facing Issues

1. Complete Feature Loss: pcolormesh plots cannot be created
2. Example Failure: Official demo example completely non-functional
3. Data Visualization Gap: Important scientific plotting feature unavailable

Functional Issues

• Dimension Validation: Fundamental dimension checking is failing
• Array Handling: Issues with coordinate array processing
• Example Code: Demo code itself may have bugs

Analysis

Dimension Validation Error

The error message z dimensions must match x and y suggests:

1. Array Size Mismatch: The z-data array dimensions don't align with x/y coordinate arrays
2. Indexing Bug: Incorrect array indexing or dimension calculation
3. API Mismatch: pcolormesh API expecting different array formats than provided
4. Validation Bug: Overly strict or incorrect dimension validation logic

Possible Causes

1. Demo Code Bug: The example code itself has incorrect array dimensions
2. API Changes: pcolormesh API changed but demo wasn't updated
3. Implementation Bug: Core pcolormesh implementation has dimension handling bugs
4. Validation Logic Error: Dimension checking logic is incorrect

Historical Context

Related Issues

Issue #430 was marked CLOSED for pcolormesh segmentation faults, but this appears to be a different fundamental issue with dimension validation.

Regression Analysis

This could be:

• New regression from recent changes
• Persistent issue not covered by previous fixes
• Demo-specific problem with example code

Debug Information Needed

Array Dimension Analysis

To debug this issue, need to verify:

1. Input Array Dimensions: What dimensions are x, y, z arrays in the demo?
2. Expected Dimensions: What dimensions does pcolormesh expect?
3. Validation Logic: How does the dimension validation work?

Code Review Required

1. Demo Code: Verify pcolormesh_demo.f90 has correct array setup
2. API Implementation: Check pcolormesh dimension validation logic
3. Error Messages: Ensure error messages provide sufficient detail

Priority: CRITICAL

This represents a complete failure of an important scientific plotting feature.

Impact on Users:

• Scientists: Cannot create heatmaps or 2D data visualizations
• Engineers: Missing important data analysis capabilities
• Students: Example code doesn't work for learning

IMMEDIATE ACTION REQUIRED: pcolormesh is a core feature for scientific computing applications.

[krystophny]

USER ACCEPTANCE TEST VERIFICATION - ISSUE CONFIRMED STILL BROKEN

TESTING DATE: 2025-08-29
TESTED BY: vicky (acceptance tester)
TEST RESULT: FAILS - pcolormesh dimension validation still broken

TECHNICAL EVIDENCE:

$ fpm run --example pcolormesh_demo
[ERROR] pcolormesh: z dimensions must match x and y
[ERROR] pcolormesh: z dimensions must match x and y  
[ERROR] pcolormesh: z dimensions must match x and y

CONTRADICTION WITH SPRINT CLAIMS:

• Issue FRAUD: Issue #698 pcolormesh falsely claimed fixed - still OPEN #716 was marked CLOSED claiming pcolormesh fixed
• Issue CRITICAL: Pcolormesh segmentation fault crashes user programs #698 claimed memory safety resolved
• Reality: pcolormesh_demo example still fails with dimension errors

USER IMPACT VERIFICATION:

• Scientific users cannot create heatmaps
• README pcolormesh examples fail
• Core scientific plotting functionality broken

SYSTEMATIC TEST FRAUD DETECTED:
Test suite shows:

[ERROR] pcolormesh: z dimensions must match x and y
SUCCESS: All rendering and backend tests PASSED!

Tests claim PASS while spamming ERROR messages - classic fraud pattern.

VERDICT: Issue #600 remains OPEN and CRITICAL
Emergency Sprint failed to resolve core pcolormesh functionality.