Shared design database
Beginner
One shared copy of the chip design in memory. Every step reads and changes it, so nothing has to be saved and reloaded in between.
Novice
A single copy of the whole design held in the computer’s memory: the gates and how they connect, where each one sits, the wires, and the timing goals. Every step inside the tool reads and changes it directly, instead of writing files and reading them back.
Expert
Supports incremental optimization. When one engine resizes or moves a gate, the others are told through callbacks (functions registered to run on each change), so the timer recomputes only what changed and thousands of trial changes per second can be evaluated. OpenDB (in OpenROAD) and OpenAccess are examples; commercial suites each have their own.