PEX

Regression model-based on-chip parasitic extraction (PEX) at the post-route stage. The tool comprises of two flows:

• Calibration Flow
• Inference Flow

Calibration Flow:

• Inputs:
  • Technology LEF
  • Cell LEF
  • PVT Libraries
  • qrcTech files
  • User-defined environment file
• Training data generation using Cadence Innovus
• Regression model training
• Output files:
  • config_file_{corner_name}.txt

The training data generation involves running a calibration script and a script to train the data. The instruction on how to run the calibration flow can be found here. The output format can be referred here.

Inference Flow:

The tool uses the constructed regression models to estimate parasitics on a given routed design.

• Inputs:
  • Technology LEF
  • Cell LEF
  • PVT Libraries
  • User-defined environment file
  • routed DEF
• Output files:
  • {design_name}.spef

The detailed information about the flow can be found here.

Getting Started

Prerequisite

• python 3.6
• Cadence Innovus 17.1 or newer
• pip 18.1
• python3-venv

Additionally, please refer to requirements.txt file in this repository. The packages in requirements.txt will be installed in a virtual environment during build.

3-party Module

• Tcl v8.4.20

Clone repo and submodules

git clone --recursive https://github.com/The-OpenROAD-Project/PEX.git

Install

cd PEX 
make clean
make build

Usage

Training flow

• This flow must be run only once for a new PDK and corner
• It involves running a tcl script that generates the required data to train the regression model.
• How to run:
  • Point to the paths of the Tech LEF, Cell LEF, qrcTech files, Liberty file, and the user-defined environment file
  • In the terminal: make calibration

Inference Flow

• How to run:
  • Point to the paths of:
    • Tech LEF
    • Cell LEF
    • Liberty file
    • Design layout (DEF)
    • Configuration file (contains regression model data)
  • In the terminal: make inference

License

The PEX repository is licensed under the BSD 3-Clause License. The flow is built and tested using a third party PDK, the Nangate45 PDK, that is licensed under a different license. The license can be found below:

• PEX: Regression model-based on-chip parasitic extraction (PEX)
• NanGate 45nm Library: open-source standard-cell library for testing and exploring EDA flows