What is path grouping, and how does it help organize timing reports and optimization?
From PDVerse STA Mentor Guide · pdVerse Mentor Guide
Explanation
group_path organizes timing paths into named groups — by clock, by endpoint type, or by custom criteria — so that reporting and optimization tools can treat different classes of paths distinctly rather than lumping everything together. Common groupings by startpoint/endpoint type include reg2reg, in2reg, reg2out, and in2out.
Timing-path Walkthrough
In a triage example, 1200 raw violating endpoints were narrowed down to 340 real violations after pessimism recovery. Categorizing those by path group revealed 210 were reg2reg setup violations traceable to one root cause, 80 were hold violations driven by skew, and 50 were in2reg violations caused by tight input delays — a breakdown only possible because the paths were organized into distinguishable groups rather than treated as one undifferentiated pile. UNEXPECTED VIOLATION Is the clock/mode correct? Is the SDC constraint correct? (check_timing) Is the library/PVT corner correct? Are parasitics (SPEF) loaded and current? Now inspect the report_timing increments
Command
group_pathExpected Report Behavior
Timing reports and optimization runs can be scoped or summarized per path group (reg2reg, in2reg, reg2out, in2out, or custom groups), making it possible to see, for example, that most violations cluster in one group with a shared root cause.
Mentor Note — Common Mistake
Treating all violating endpoints as one undifferentiated list, missing that most of them share a single root cause traceable through path grouping (as in the reg2reg cluster in the triage example).
How To Debug
Use path groups to categorize a large batch of violations by startpoint/endpoint type or clock, then look for clusters that share a root cause rather than debugging each violation individually.
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