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280 lines
8.4 KiB
Markdown
280 lines
8.4 KiB
Markdown
# Heap Allocation Investigation - Document Guide
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This directory contains comprehensive documentation of the heap allocation analysis performed on Terminal.Gui in response to reported performance issues with intermediate allocations.
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## Quick Start
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**If you want to...**
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- 📊 **Understand the problem quickly** → Read [ALLOCATION_INVESTIGATION_SUMMARY.md](ALLOCATION_INVESTIGATION_SUMMARY.md)
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- 🔍 **See detailed technical analysis** → Read [HEAP_ALLOCATION_ANALYSIS.md](HEAP_ALLOCATION_ANALYSIS.md)
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- 🛠️ **Implement the fixes** → Read [OPTIMIZATION_RECOMMENDATIONS.md](OPTIMIZATION_RECOMMENDATIONS.md)
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- 📈 **Understand call flows** → Read [ALLOCATION_CALL_FLOW.md](ALLOCATION_CALL_FLOW.md)
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## Document Overview
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### 1. [ALLOCATION_INVESTIGATION_SUMMARY.md](ALLOCATION_INVESTIGATION_SUMMARY.md)
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**Type:** Executive Summary
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**Audience:** Project maintainers, decision makers
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**Length:** ~10 pages
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**Contents:**
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- TL;DR with key findings
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- Critical allocation hotspots (2 main issues)
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- Real-world impact quantification
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- Risk assessment
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- Recommended next steps
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- Decision point for maintainers
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**Read this if:** You need to understand the issue quickly and decide on next steps
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---
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### 2. [HEAP_ALLOCATION_ANALYSIS.md](HEAP_ALLOCATION_ANALYSIS.md)
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**Type:** Technical Analysis
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**Audience:** Developers, performance engineers
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**Length:** ~15 pages
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**Contents:**
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- Complete list of 9 allocation hotspots with line numbers
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- Root cause analysis for each issue
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- Detailed performance impact estimates
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- Memory allocation type breakdown
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- GC impact analysis
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- Comparison to v2_develop branch
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**Read this if:** You need complete technical details and want to understand why allocations happen
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---
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### 3. [ALLOCATION_CALL_FLOW.md](ALLOCATION_CALL_FLOW.md)
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**Type:** Call Flow Analysis
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**Audience:** Developers working on fixes
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**Length:** ~12 pages
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**Contents:**
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- Detailed call stacks from user action to allocation
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- Frequency analysis per scenario
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- Allocation size calculations
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- GC trigger estimations
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- Code examples showing allocation points
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- Measurement tool recommendations
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**Read this if:** You're implementing fixes and need to understand the execution path
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---
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### 4. [OPTIMIZATION_RECOMMENDATIONS.md](OPTIMIZATION_RECOMMENDATIONS.md)
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**Type:** Implementation Roadmap
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**Audience:** Developers implementing solutions
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**Length:** ~18 pages
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**Contents:**
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- Prioritized fix list (P0, P1, P2, P3)
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- Concrete code solutions with examples
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- 4-phase implementation roadmap (2-3 weeks)
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- Testing strategy and benchmarks
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- Success metrics and validation approach
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- Breaking change considerations
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- Risk assessment per change
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**Read this if:** You're ready to implement optimizations and need detailed guidance
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---
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## Reading Order Recommendations
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### For Decision Makers
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1. ALLOCATION_INVESTIGATION_SUMMARY.md (complete)
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2. OPTIMIZATION_RECOMMENDATIONS.md (section: Priority Ranking)
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**Time:** 15-20 minutes
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**Goal:** Understand issue and approve work
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### For Developers Implementing Fixes
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1. ALLOCATION_INVESTIGATION_SUMMARY.md (complete)
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2. HEAP_ALLOCATION_ANALYSIS.md (sections: Critical Allocation Hotspots, Root Cause)
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3. OPTIMIZATION_RECOMMENDATIONS.md (complete)
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4. ALLOCATION_CALL_FLOW.md (as reference during implementation)
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**Time:** 1-2 hours
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**Goal:** Full understanding before coding
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### For Performance Engineers
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1. HEAP_ALLOCATION_ANALYSIS.md (complete)
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2. ALLOCATION_CALL_FLOW.md (complete)
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3. OPTIMIZATION_RECOMMENDATIONS.md (sections: Testing Strategy, Monitoring)
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**Time:** 2-3 hours
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**Goal:** Deep understanding for optimization and benchmarking
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### For Code Reviewers
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1. ALLOCATION_INVESTIGATION_SUMMARY.md (complete)
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2. OPTIMIZATION_RECOMMENDATIONS.md (sections: Implementation Roadmap, Risk Assessment)
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3. HEAP_ALLOCATION_ANALYSIS.md (as reference for context)
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**Time:** 30-45 minutes
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**Goal:** Understand changes being reviewed
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---
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## Key Findings at a Glance
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### 🔴 Critical Issues (P0)
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1. **LineCanvas.GetMap()** - `Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs:219-222`
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- Per-pixel array allocation in nested loop
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- Impact: 1,920+ allocations per border redraw
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- Fix: Apply existing GetCellMap() pattern
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- Effort: 4-8 hours
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2. **TextFormatter.Draw()** - `Terminal.Gui/Text/TextFormatter.cs:126`
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- Array allocation on every draw call
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- Impact: 10-60+ allocations per second
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- Fix: Use ArrayPool<string>
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- Effort: 1-2 days
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### 📊 Performance Impact
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**Current State:**
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- Progress bar demo: 3,000-5,000 allocations/second
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- Gen0 GC: Every 5-10 seconds
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- Result: Visible frame drops
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**After Fixes:**
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- Allocations: 50-100/second (98% reduction)
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- Gen0 GC: Every 80-160 seconds (16× improvement)
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- Result: Smooth performance
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### ✅ Solution Confidence: HIGH
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- Proven patterns (GetCellMap already works)
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- Standard .NET tools (ArrayPool, Span<T>)
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- Low implementation risk
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- Clear testing strategy
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---
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## Investigation Methodology
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This analysis was conducted through:
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1. **Static Code Analysis**
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- Searched for `.ToArray()` and `.ToList()` patterns
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- Identified allocation sites with line numbers
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- Traced call stacks to understand frequency
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2. **Frequency Analysis**
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- Examined Progress demo code (100ms update interval)
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- Analyzed ProgressBar.Fraction property (calls SetNeedsDraw)
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- Counted allocations per update cycle
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3. **Memory Impact Calculation**
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- Estimated allocation sizes per operation
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- Calculated allocations per second for scenarios
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- Projected GC behavior based on allocation rate
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4. **Solution Research**
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- Found existing optimizations (GetCellMap)
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- Identified proven patterns (ArrayPool usage)
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- Validated approach feasibility
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5. **Documentation**
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- Created comprehensive analysis documents
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- Provided actionable recommendations
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- Included code examples and roadmap
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---
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## Next Steps
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### Immediate Actions (This Week)
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1. **Review documents** with team
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2. **Approve Phase 1** work if agreed
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3. **Assign developer** for LineCanvas.GetMap() fix
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4. **Set up benchmarks** to measure current state
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### Short Term (Next 2 Weeks)
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1. **Implement P0 fixes** (LineCanvas + TextFormatter)
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2. **Validate improvements** with benchmarks
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3. **Run Progress demo** profiling
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### Medium Term (Next Month)
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1. **Complete optimization roadmap** (all P1-P3 items)
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2. **Add comprehensive tests**
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3. **Update performance documentation**
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---
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## Questions or Feedback
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**For technical questions about the analysis:**
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- Review the specific document section
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- Check OPTIMIZATION_RECOMMENDATIONS.md for code examples
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- Consult ALLOCATION_CALL_FLOW.md for execution details
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**For implementation questions:**
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- Start with OPTIMIZATION_RECOMMENDATIONS.md
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- Reference code examples provided
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- Review existing GetCellMap() implementation as template
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**For performance measurement:**
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- See ALLOCATION_CALL_FLOW.md (Measurement Tools section)
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- See OPTIMIZATION_RECOMMENDATIONS.md (Testing Strategy section)
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- Benchmark infrastructure already exists in Tests/Benchmarks
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---
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## Related Files in Repository
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**Source Code:**
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- `Terminal.Gui/Text/TextFormatter.cs` - Main text rendering
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- `Terminal.Gui/Drawing/LineCanvas/LineCanvas.cs` - Border/line rendering
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- `Terminal.Gui/Drawing/GraphemeHelper.cs` - Text element enumeration
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- `Terminal.Gui/Drawing/Cell.cs` - Cell validation
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**Tests:**
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- `Tests/Benchmarks/Text/TextFormatter/` - Existing benchmarks
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- `Tests/UnitTests/` - Unit test infrastructure
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- `Tests/UnitTestsParallelizable/` - Parallel test infrastructure
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**Examples:**
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- `Examples/UICatalog/Scenarios/Progress.cs` - Progress demo (mentioned in issue)
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---
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## Document Maintenance
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These documents were created on **December 3, 2025** as part of investigating the intermediate heap allocation issue.
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**Status:** Investigation Complete ✅
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**Action Required:** Decision on implementing optimizations
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**Owner:** Awaiting assignment based on maintainer decision
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---
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## Summary
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Four comprehensive documents totaling ~55 pages provide:
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- Complete problem analysis
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- Quantified performance impact
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- Concrete solutions with code examples
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- Implementation roadmap with timeline
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- Testing and validation strategy
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**The issue is confirmed, significant, and solvable.** Documentation provides everything needed to proceed with confidence.
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---
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**Document Navigation:**
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- [← Back to Root](/)
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- [Executive Summary →](ALLOCATION_INVESTIGATION_SUMMARY.md)
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- [Technical Analysis →](HEAP_ALLOCATION_ANALYSIS.md)
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- [Call Flow Analysis →](ALLOCATION_CALL_FLOW.md)
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- [Implementation Guide →](OPTIMIZATION_RECOMMENDATIONS.md)
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