ZlibBoost

Introduction

ZlibBoost is an open-source framework designed for standard cell library characterization.It offers multi-threaded simulation capabilities for both sequential and combinational cells, supporting industry-standard simulators like Spectre and HSPICE, as well as the open-source simulator Ngspice. The tool uses separate TCL files for configuration parameters and template parameters, providing a structured and organized approach. Examples of library characterization are provided using the open-source FreePDK45 technology nodes.

Quickstart (Python 3.13 required)

Dependencies

Runtime Python dependencies (from pyproject.toml):

• numpy>=1.26
• ttable>=0.7.0

Option A: uv (recommended)

This repository includes a pyproject.toml for uv. From the repo root:

uv python install 3.13
uv sync
uv run zlibboost -c examples/config_f45.tcl

Option B: Python 3.13

If you prefer a direct Python setup, install the minimal dependencies and run the module:

python3.13 -m pip install -U numpy ttable
python3.13 -m zlibboost.cli.main -c examples/config_f45.tcl

Usage & Example

To run a simulation, specify the necessary parameters according to your simulation requirements. The parameters can be provided in a configuration file or directly on the command line, depending on the implementation of your simulation framework.

❯ python -m zlibboost.cli.main -h                        

  ______ _ _     ____                  _   
 |__  / (_) |__ | __ )  ___   ___  ___| |_ 
   / /| | | '_ \|  _ \ / _ \ / _ \/ __| __|
  / /_| | | |_) | |_) | (_) | (_) \__ \ |_ 
 /____|_|_|_.__/|____/ \___/ \___/|___/\__|                                  

usage: zlibboost [-h] [-c CONFIG] [--simulate | --no-simulate]

options:
  -h, --help            show this help message and exit
  -c, --config CONFIG   Config TCL file (repeatable). Template files referenced inside the config will be auto-detected.
  --simulate, --no-simulate
                        Run simulations after deck generation. Use --no-simulate to skip.

python -m zlibboost.cli.main -c examples/config_f45.tcl

Configuration Parameters

Configuration parameters are provided via set_var <name> <value> in the config TCL files passed to -c/--config. The refactored CLI merges config files in order and auto-detects the timing TCL from template_file. Required by the pipeline: extsim_deck_dir, template_file, spicefiles, and report_path.

Command	Example	Description
extsim_deck_dir	./spice_deck	Output directory for generated SPICE decks.
template_file	./t65.tcl	Timing/characterization TCL file (auto-detected by CLI).
spicefiles	./examples/sky130/netlist	Directory containing cell netlists.
spicefiles_format	sp	Netlist file extension (sp/spi/scs/spice); defaults by simulator.
modelfiles	./models/tt.scs	Model include path; used with .inc or .lib directives.
lib_corner	tt	Optional corner name for .lib; omit to use .inc.
report_path	./report	Output directory for JSON/Liberty exports and pipeline reports.
simulate_out_dir	./t65_spectre	Optional simulation output root; defaults to deck output directory.
simulate_types	hidden,leakage,delay	Optional sim type filter (comma/space separated; hidden/leakage/delay/setup/hold/recovery/removal/mpw).
spice_simulator	spectre	SPICE engine: spectre, hspice, ngspice.
voltage	1.2	Supply voltage (V).
temp	25	Temperature (C).
threads	4	Worker threads for simulation scheduler.
vdd_name	VDD	VDD net name in decks.
gnd_name	VSS	Ground net name in decks.
vpw_name	VPB	Optional p-well net name (set with vnw_name).
vnw_name	VNB	Optional n-well net name (set with vpw_name).
gnw_name	VNB	Sky130 n-well net name (stored for compatibility).
delay_inp_rise	0.5	Input rise threshold for delay measurement.
delay_inp_fall	0.5	Input fall threshold for delay measurement.
delay_out_rise	0.5	Output rise threshold for delay measurement.
delay_out_fall	0.5	Output fall threshold for delay measurement.
measure_slew_lower_rise	0.3	Lower threshold for rise slew measurement.
measure_slew_upper_rise	0.7	Upper threshold for rise slew measurement.
measure_slew_lower_fall	0.3	Lower threshold for fall slew measurement.
measure_slew_upper_fall	0.7	Upper threshold for fall slew measurement.
measure_cap_lower_rise	0.2	Lower threshold for rise capacitance measurement.
measure_cap_upper_rise	0.8	Upper threshold for rise capacitance measurement.
measure_cap_lower_fall	0.2	Lower threshold for fall capacitance measurement.
measure_cap_upper_fall	0.8	Upper threshold for fall capacitance measurement.
mpw_search_bound	5e-9	Initial search bound for min pulse width measurements.
driver_waveform	2	Driver waveform type: 1=linear, 2=exp, 3=mixed.
subtract_hidden_power	0	Legacy switch for hidden-power subtraction (stored in config).
arc_mode	1	Legacy arc flag; auto-arc is controlled by ZLIBBOOST_AUTO_ARC.

Template Parameters

The template (timing/characterization) TCL defines cells, templates, arcs, and waveforms. These commands are parsed after the config files and can be mixed with set_var if needed.

Command	Description
set cells	Specify the cells to be characterized.
define_driver_waveform	Defines the input waveform used to stimulate the cell during characterization.
define_template	Defines a template to be used for characterization.
define_cell	Defines how a cell is to be characterized.
define_function	Defines the logical function of the cell.
define_leakage	Defines the logic conditions under which leakage power is calculated for the selected cells.
define_arc	Specify a user-defined arc to override automatic arc determination

Note: waveform shape selection uses driver_waveform (config) or DRIVER_WAVEFORM_TYPE (env); the -type field in define_driver_waveform is preserved as metadata.

Environment Variables

The refactored CLI also accepts environment variables:

Variable	Example	Description
ZLIBBOOST_LOG_LEVEL	DEBUG	Logging level (DEBUG/INFO/WARNING/ERROR/CRITICAL).
ZLIBBOOST_SIM_ENGINE	spectre	Simulation engine override (spectre/hspice/ngspice/mock).
ZLIBBOOST_SIMULATE	0	Default for simulation when --simulate/--no-simulate is not set.
ZLIBBOOST_AUTO_ARC	1	Enable/disable auto arc generation (default on).
ZLIBBOOST_SIM_TYPES	hidden,leakage,delay	Fallback sim type filter if simulate_types is not set in config.
DRIVER_WAVEFORM_TYPE	2	Driver waveform shape (1=linear, 2=exp, 3=mixed); usually set via config.

Related Project

• ZlibValidation — Command line tool to validate standard cell libraries in .lib format.

Citation

If you use ZlibBoost for your research or industrial applications, please cite the following paper and our project：

@article{10.1145/3747182,
author = {Chen, Zhengrui and Guo, Chengjun and Wang, Shizhang and Feng, Guozhu and Song, Zixuan and Wu, Zhenhua and Yin, Xunzhao and Song, Weiquan and Zhang, Li and Yan, Zheyu and Zhuo, Cheng},
title = {ZlibBoost: An Efficient and Flexible Open-Source Framework for Standard Cell Characterization},
year = {2025},
publisher = {Association for Computing Machinery},
address = {New York, NY, USA},
issn = {1084-4309},
url = {https://doi.org/10.1145/3747182},
doi = {10.1145/3747182},
note = {Just Accepted},
journal = {ACM Trans. Des. Autom. Electron. Syst.},
month = jul,
keywords = {Standard cell, Library characterization, Machine learning}
}

Note: This codebase is an improved version of the one discussed in our paper, while the underlying logic remains consistent.