MinAC Overview

Given any input distribution and error bound, this project implements the exact-synthesis method to automatically produce minimal-area approximate 4-2 compressors. To directly obtain an area-optimal circuit using an industrial gate library, gates with multiple outputs are taken into account during the exact synthesis.

Requirements

OS: 64-bit Linux
gcc
g++
EDA logic synthesis tools: ABC executable file
SMT Solver: Z3

Important Notes

Since the program requires the EDA tools ABC,MVSIS, and SMT Solver Z3, please download the appropriate executable files or compile the source codes in your OS.
For ABC, suppose the absolute directory containing the executable file abc is <abc_exe_absolute_directory>. Then, before compiling the MinSC program, please execute command: cp abc_exe_absolute_directory /usr/bin/abc, which ensures ABC can run in an arbitrary path.

Getting Started

Configuration in Project

Install Z3 at a self-defined path Z3_Path
Set up a C++ project;
Add the source files and header files in the folder src/;
Configure the library path of Z3 for this project:

Project->Property->
- GCC C++ Complier->Includes->Include paths->Add->: Z3_Path\src\api;
- GCC C++ Complier->Includes->Include paths->Add->: Z3_Path\src\api\c++;
- GCC C++ Linker->Library search path(-L)->Add： Z3_Path\build;
- GCC C++ Linker->Libraries(-l)->Add： z3;

Input Format

errorBound e_b : the MED error bound of the approximate 4-2 compressors.
In our experiment, the inputs are set as uniformly distributed. Thus, the error bound errorBound e_b is represented as e_b/256, where the numerator is an integer. For each existing design, we calculate its MED e_b. Then, MinAC is applied to synthesize approximate 4-2 compressors with MED no more than e_b. Below is the MED of approximate 4-2 compressors from Reference papers.
```
approximate 4-2 compressors    MED `e_b`
 -------------------------------------
 Momeni[3]                    100
 Venka[4]                     37
 Yang1[5]                     1
 Yang2[5]                     10
 Yang3[5]                     16
 Lin[2]                       2
 Ha[6]                        16
 Akbar1[7]                    116
 Akbar2[7]                    38
 Ahma[8]                      55
 Strollo[9]                   4
```

Program Organization

<program_dir>
| readme.md
|----src
|     |----(source files)
|----gate_library_MinAC
|     |----nangate_45nm_typ.lib
|     |----gate_multiple_output.txt(the gate library after extending nangate_45nm_typ.lib)
|----input_dir
|     |----vector42.txt (the PO number, PI number-PO number, and the truth table of the exact 4-2 compressor)
|----temp_dir
|     |----(temporary files)
|----output_MinAC
|     |----medBound116
|     |     |----solution0.v
|     |     |----summary0.txt
|     |     |----solution1.v
|     |     |----summary1.txt
|     |     |----bestSol_summary.txt
|     |----(and so on)
|----examples_demo_results
|     |----medBound116
|     |     |----solution0.v
|     |     |----summary0.txt
|     |     |----solution1.v
|     |     |----summary1.txt
|     |     |----bestSol_summary.txt
|     |----(and so on)

src: contains all source files and header files.
gate_library_MinAC: contains the nangate_45nm_typ.lib and gate_multiple_output.txt. The file gate_multiple_output.txt is the gate library after extending nangate_45nm_typ.lib. For a gate with the input number less than 4 or the output number less than 2, it is extended to a 4-input 2-output gate.
input_dir: contains the input file called vector42.txt. Format of each row in the vector42.txt file:

   First row: (PI number) (PO number)
   Second row: the truth table of the exact 4-2 compressor, which is represented as the binary encoded number of all PO values.

temp_dir: contains temporary files generated during the running of the program.
output_MinAC: contains ten sub-folders with different MED bound e_b. For each sub-folder, it contains the following files:
- bestSol_summary.txt: the overall summary of the best solution with minimal area.
- solution<num>.v: the gate-level Verilog file for the solution with number <num>.
- summary<num>.txt: the summary of the solution with number <num>.
  Different solution<num>.v are the solution Verilog files with different gate numbers. solution0.v is the verilog file with the smallest gate number r_min which satisfies the error requirement. Other verilog files solution<num>.v are the circuit with gate number r_min+num which satisfy the error requirement. For these Verilog files, we choose the circuit with the smallest area as the best solution, and the summary of the best solution is stored in bestSol_summary.txt.
examples_demo_results: contains ten sub-folders with different MED bound e_b. The MED bound e_b is set as our paper [1]. For each sub-folder, it contains the following files:
- bestSol_summary.txt: the overall summary of the best solution with minimal area.
- solution<num>.v: the gate-level Verilog file for the solution with number <num>.
- summary<num>.txt: the summary of the solution with number <num>.

If you have any questions or suggestions, please feel free to eamil to xuan.wang@sjtu.edu.cn, thanks!

SJTU-ECTL / MinAC