MECALS

MECALS: maximum error checking technique for approximate logic synthesis.

This tool synthesizes approximate circuits under the maximum error constraint, such as worst-case error (WCE) and maximum square error (MaxSE) constraint. Its diagram is as follows.

Publication

C. Meng, J. Sun, Y. Mai, W. Qian, “MECALS: a maximum error checking technique for approximate logic synthesis,” in ACM/IEEE Design, Automation & Test in Europe Conference & Exhibition (DATE), Antwerp, Belgium, 2023.

Dependencies

• Reference environment, Ubuntu 20.04 LTS with the following tools and libraries:

  • gcc 10.3.0 & g++ 10.3.0

    You can install these tools with the following command:

    sudo apt install gcc-10
    sudo apt install g++-10

    You also need to check whether the default versions of gcc and g++ are 10.3.0:

    gcc --version
    g++ --version

    If the default versions of gcc and g++ are not 10.3.0, please change them to 10.3.0.

  • cmake 3.16.3

    You can install the tool using the following command:

    sudo apt install cmake

  • yosys

    You can install the tool using the following command:

    sudo apt install yosys

  • abc

    You need to manually compile abc and add the path where the executable program abc locates to the environment variable.

  • libboost 1.75.0

    You can download libboost 1.75.0, manually compile it, and then install it.

  • libreadline 8.0-4

    You can install the library using the following command

    sudo apt install libreadline-dev

• Alternatively, we package a docker image containing the above dependencies:

  https://hub.docker.com/r/changmeng/als_min

How to Download

This project relies on two submodules:

• Open-source logic synthesis and verification tool abc
• Open-source logic synthesis tool espresso

There are two ways of downloading this project:

1. Clone the project, and then update the submodules:

git clone https://github.com/SJTU-ECTL/MECALS.git
git submodule init
git submodule update

2. Alternatively, clone the project as well as the submodules:

git clone --recursive https://github.com/SJTU-ECTL/MECALS.git

How to Build

• To build, go to the root directory of the project, and then execute:

mkdir build
cd build
cmake ..
make
cd ..

An executable program called als.out will be generated at the project root directory.

• To clean up, go to the root directory of the project, and then execute:

rm -r build

How to Run

• Example command:

./als.out -i input/benchmark/aig/mac.aig -m input/miter/width_8_wce_31.aig -l ./input/standard-cell/nangate_45nm_typ.lib -o tmp/ -p 1.0 --fSASIMI 1

In this example,

• The tool inputs the accurate circuit "input/benchmark/aig/mac.aig"

• The error constraint is specified by the error miter "input/miter/width_8_wce_31.aig". A general error miter is shown below.

  

  In the file "input/miter/width_8_wce_31.aig", both the outputs of exact and approximate circuits, $\mathbf y$ and $\mathbf {\hat y}$, have a bit width of 8. The WCE bound $B=31$, which means WCE should not exceed 31.

• It uses the standard cell library "./input/standard-cell/nangate_45nm_typ.lib" for technology mapping.

• The approximate circuits will be outputted to the folder ./tmp

Configurations

Use the following command to get help:

./als.out -h

The following information will be returned:

usage: ./als.out --accCirc=string --mitCirc=string [options] ... 
options:
  -i, --accCirc         path to accurate circuit (string)
  -m, --mitCirc         path to miter circuit (string)
  -a, --appCirc         path to approximate circuit; if this option is not empty, then error checking is performed (string [=])
  -l, --standCell       path to standard cell library (string [=input/standard-cell/nangate_45nm_typ.lib])
  -o, --outpPath        path to approximate circuits (string [=tmp/])
  -s, --seed            seed (unsigned int [=0])
  -f, --nFrame          #simulation patterns (int [=8192])
      --fSASIMI         flag of using SASIMI (int [=1])
  -p, --exactPBDPerc    proportion of exact PBD (double [=1])
  -h, --help            print this message

Long parameter	Short parameter	Default value	Function
--accCirc	-i	None	Path to accurate circuit, e.g., input/benchmark/aig/mac.aig
--mitCirc	-m	None	Path to error miter circuit, e.g., input/miter/width_8_wce_31.aig. You can find more error miters in the folder input/miter/. To specify an arbitrary miter, you can refer to the functions GenWCEMit and GenMaxSEMit in the Python code script/run.py
--appCirc	-a	""	Path to approximate circuit. When "--appCirc" specifies a non-empty string, then the program will iteratively simplify the accurate circuit provided by "--accCirc". Otherwise, if "--appCirc" specifies an empty string "", then the program will check the maximum error of the approximate circuit provided by "--appCirc", compared to the accurate circuit provided by "--accCirc".
--standCell	-l	input/standard-cell/mcnc.genlib	Path to standard cell library, e.g., ./input/standard-cell/nangate_45nm_typ.lib
--outpPath	-o	tmp	Specify the directory where the approximate circuits are outputed.
--seed	-s	0	The seed used for generating random input patterns for logic simulation. When seed "0" is used, then the program randomly picks a seed. Otherwise, the program uses the specified seed.
--nFrame	-f	8192	The number of random input patterns in logic simulation. In our work, simulation is used for quickly filtering some invalid local approximate changes (LACs).
--fSASIMI		1	Whether to use SASIMI LAC or not. If "--fSASIMI" is set to 1, then both SASIMI and CONST LACs will be applied. Otherwise, if "--fSASIMI" is set to 0, then only the CONST LAC will be applied. Please refer to our paper to see the definitions of LACs.
--exactPBDPerc	-p	1	The proportion of nodes using exact partial Boolean difference. This value is a float-point number, ranging from 0.0 to 1.0. Its detailed definition is introduced in our paper.
--help	-h	None	Print help.