perf: cache traced field conversion

[yaugenst-flex]

Greptile Overview

Updated On: 2025-11-07 12:55:45 UTC

Greptile Summary

Adds _has_tracers cache to optimize tracer field conversion by short-circuiting when objects have no autograd tracers.

Major changes:

• Added _has_tracers private attribute to cache tracer presence status
• Modified _strip_traced_fields() to set cache and return early when no tracers exist
• Updated to_static() to leverage cache for performance
• Fixed type hint for starting_path parameter (tuple[str, ...] instead of tuple[str])
• Cache is properly invalidated in copy() method

Critical issue found:

• The _has_tracers cache is object-level but _strip_traced_fields() accepts a starting_path parameter to check only a subset of the object
• Early return at line 1079 incorrectly uses the global cache even when checking a specific path
• This can cause incorrect results: if full object has no tracers but a specific path does (or vice versa), the cached value will give wrong results for path-specific queries

Confidence Score: 1/5

• This PR contains a critical logic bug that will cause incorrect behavior when checking for tracers in specific paths
• The caching mechanism has a fundamental design flaw where an object-level cache is used for path-specific queries. This will definitely cause incorrect results in production when _strip_traced_fields() is called with different starting_path values, which happens in the autograd workflow (e.g., starting_path=("structures",) and starting_path=("data",)). The bug is deterministic and will affect correctness of autograd operations.
• The caching logic in tidy3d/components/base.py needs to be redesigned to either track cache per-path or avoid caching for path-specific queries

Important Files Changed

File Analysis

Filename	Score	Overview
tidy3d/components/base.py	1/5	adds _has_tracers cache for performance but has critical logic bug where object-level cache is used incorrectly for path-specific queries, causing incorrect results when different starting_path values are used

Sequence Diagram

sequenceDiagram
    participant Client
    participant BaseModel as Tidy3dBaseModel
    participant Cache as _has_tracers cache
    
    Note over Client,Cache: Scenario 1: Initial check with no path
    Client->>BaseModel: to_static()
    BaseModel->>BaseModel: _strip_traced_fields()
    BaseModel->>BaseModel: handle_value() recursively
    alt No tracers found
        BaseModel->>Cache: _has_tracers = False
        BaseModel->>Client: return self (early exit)
    else Tracers found
        BaseModel->>Cache: _has_tracers = True
        BaseModel->>BaseModel: get_static() on fields
        BaseModel->>BaseModel: _insert_traced_fields()
        BaseModel->>Cache: static_self._has_tracers = False
        BaseModel->>Client: return static_self
    end
    
    Note over Client,Cache: Scenario 2: Check with starting_path
    Client->>BaseModel: _strip_traced_fields(starting_path=("structures",))
    alt _has_tracers is False
        Note over BaseModel,Cache: BUG: Returns early even though<br/>cache is for full object, not this path
        BaseModel->>Client: return dict_ag() (incorrect!)
    else _has_tracers is None or True
        BaseModel->>BaseModel: self.dict()[starting_path]
        BaseModel->>BaseModel: handle_value() on subset
        alt Field mapping found
            BaseModel->>Cache: _has_tracers = True (incorrect for path-specific!)
            BaseModel->>Client: return dict_ag(field_mapping)
        else No mapping
            Note over BaseModel,Cache: Cache not updated for path-specific check
            BaseModel->>Client: return dict_ag()
        end
    end

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[momchil-flex]

Thanks, just wondering if adding another cache is worth it as just the _has_tracers already solves the original problem. Not sure e.g. how fast cache is compared to doing the actual field mapping.

[greptile-apps]

_{1 file reviewed, 2 comments}

_{Edit Code Review Agent Settings | Greptile}

[github-actions]

Diff Coverage

Diff: origin/develop...HEAD, staged and unstaged changes

• tidy3d/components/base.py (100%)

Summary

• Total: 21 lines
• Missing: 0 lines
• Coverage: 100%