Library Set & Opcond Mapping: Reports & Metrics

Reports and metrics

Reports & Metrics for Library Set & Opcond Mapping focuses on library mismatch count, opcond alignment errors, derate mapping gaps. The goal is to connect the observable symptom to timing mechanism, ownership, and regression risk.

The job of a report is to turn library mismatch count, opcond alignment errors, derate mapping gaps into a closure decision. A single WNS number is almost never enough; you need path group breakdown, cell vs net split, and a clear gap between current slack and signoff target.

Metric movement

METRIC GRAPH — library mismatch count, opcond alignment errors, derate mapping gaps

WNS (ps)
  ^
  |                         target (0)
  |                       - - - - - - -
  |                  o after ECO + hold check
  |              o
  |         o baseline run
  |    o failing regression
  +--------------------------------------> closure iteration
    view audit     path group fix     MMMC signoff

Readout:
  - explain why WNS/TNS moved and which path group drove the change

Slack distribution

SLACK HISTOGRAM — Library Set & Opcond Mapping

path count
  |      ***
  |    *******
  |  ***********
  |*************  <- WNS (worst path)
  +--------------------> slack (ns)
  -0.15  0.0  0.10

Fix the left tail first; average slack misleads.

• Track library mismatch count, opcond alignment errors, derate mapping gaps by path group, corner, and analysis view.

• Report WNS/TNS and failing endpoint count together.

• Include setup and hold splits; they often diverge after ECO.

• Always store the metric next to the artifact that produced it.

STA deep dive

Signoff WNS is the minimum across the full scenario matrix.

Concept diagram

MMMC

corners (ss/tt/ff) x modes (func/test) x views (signoff RC)
= scenario set -> min(WNS) is signoff

Metric graph

WNS HEATMAP BY CORNER

        ss    tt    ff
setup  -80   +10   +5
hold   -15   -2    -8

Reports and artifacts

• per-corner WNS

• mode summary

• lib map audit

• view delta

Mini case study

Passed TT typical but failed SS hold — signoff matrix was incomplete; added low-voltage mode.

Debug branches

• Isolate failing scenario first

• Never compare unlike SPEF tags

Senior review question

Ask: what corner/mode/view proves this topic is closed or failing?

Key takeaways

• State corner, mode, view, and database tag with every slack claim.

• Run setup and hold plus MMMC regression after every ECO.

Common pitfalls

• Comparing STA runs with different SPEF or SDC tags.

• Broad false_path to green-wash violations.

• Setup-only ECO without hold check.

Reading reports