gp-append-nil-slice — append on nil slice vs make(...,0,len)
Claim
Measured on this machine: primary hot case append_grow ratio before/after ~7.28× (faster after). Default severity stays hint. Do not escalate to error from this fill alone — ratio is strong but policy/default and G3 OK-idiom history keep severity unchanged.
How measured
- Harness:
packages/goperf/examples/bench/evidence_gp.go - Protocol: warm=3; median of 9 rounds; GC/collect where applicable
- Raw lines:
gp-append-nil-slice.jsonl
Runtime (this evidence file)
| Field | Value |
|---|---|
| When | 2026-10-23 Asia/Shanghai (machine clock; JSONL ts is UTC) |
| Toolchain | go1.27.3 |
Median after (presize_make) | 0.336292 ms (ops=500000, ratio=1.000000) |
Median before (append_grow) | 2.448459 ms (ops=500000, ratio=7.280753) |
Median after (small_presize) | 0.000167 ms (ops=100, ratio=1.000000) |
Median before (small_append_grow) | 0.000166 ms (ops=100, ratio=0.994012) |
| Primary ratio before/after | ~7.28× (append_grow) |
Direction and absolute ms are N/machine/opt-sensitive. Re-run the harness after toolchain or machine changes.
Lint mapping
goperf-lint gp-append-nil-slice default stays hint. Escalate recommended: no.
Limits
- Microbench; not an app profile.
- Small-N rows may sit near timer noise; prefer hot (non-small) cases for ratio claims.
- I/O rules (print/echo/puts/writeln) discard to
/dev/null— env-dependent.