Skip to content

ADR-0480: Bootstrap Score Name-Builder Deduplication

  • Status: Accepted
  • Date: 2026-05-16
  • Deciders: lusoris, Claude (Anthropic)
  • Tags: refactor, predict, libvmaf

Context

Two functions in the libvmaf core engine each construct the same four bootstrap score-name strings (suffix _bagging, _stddev, _ci_p95_lo, _ci_p95_hi) appended to a model-collection name:

  • bootstrap_append_named_scores() in core/src/predict.c (per-frame path)
  • vmaf_score_pooled_model_collection() in core/src/libvmaf.c (pooling path)

Both functions duplicate the same literal suffix strings and the same name-buffer size formula (strlen(name) + strlen(longest_suffix) + 1). Both left //TODO: dedupe comments referencing each other. The duplication was noted during the TODO/FIXME audit of 2026-05-16.

Deduplication carries a real correctness benefit: if a new suffix is ever added or an existing one is renamed, both call sites must be updated. A single shared header closes that divergence window.

Decision

Extract the four suffix string constants and the BOOTSTRAP_NAME_BUF_SZ() macro into a new internal-only header core/src/bootstrap_names.h. Both predict.c and libvmaf.c include this header; the TODO comments are replaced with a citation to this ADR. The underlying loops cannot be merged further because the callee functions differ (vmaf_feature_collector_append vs vmaf_feature_score_pooled); introducing a function-pointer indirection for two call sites would add more complexity than it removes.

Alternatives considered

Option Pros Cons Why not chosen
Full helper function (function-pointer callback) Single loop body Adds typedef/callback indirection; reduces readability; more code than it replaces Complexity exceeds benefit for two call sites
Leave TODOs as-is Zero change Divergence risk grows as new suffixes are added Does not close the audit finding
Inline the suffix constants as named #define in each .c No new file Still duplicated across two translation units Does not close the divergence window

Consequences

  • Positive: suffix constants are now a single source of truth; the BOOTSTRAP_NAME_BUF_SZ() formula is defined once; the two //TODO markers are removed.
  • Negative: one new internal header file to maintain.
  • Neutral: no ABI or behaviour change; no test regeneration required.

References

  • core/src/bootstrap_names.h (new file)
  • core/src/predict.c — bootstrap_append_named_scores()
  • core/src/libvmaf.c — vmaf_score_pooled_model_collection()
  • TODO/FIXME audit: .workingdir/audit-todo-fixme-2026-05-16.md items #1 and #2