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https://github.com/stanford-centaur/pono

Pono: A flexible and extensible SMT-based model checker
https://github.com/stanford-centaur/pono

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Pono: A flexible and extensible SMT-based model checker

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README 

        
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# Pono: A Flexible and Extensible SMT-Based Model Checker

Pono is a performant, adaptable, and extensible SMT-based model checker implemented in C++. It leverages [Smt-Switch](https://github.com/stanford-centaur/smt-switch), a generic C++ API for SMT solving. Pono was developed as the next

generation of [CoSA](https://github.com/cristian-mattarei/CoSA) and thus was originally named _cosa2_.



[Pono](http://wehewehe.org/gsdl2.85/cgi-bin/hdict?e=q-11000-00---off-0hdict--00-1----0-10-0---0---0direct-10-ED--4--textpukuielbert%2ctextmamaka-----0-1l--11-en-Zz-1---Zz-1-home-pono--00-3-1-00-0--4----0-0-11-10-0utfZz-8-00&a=d&d=D18537) is the Hawaiian word for proper, correct, or goodness. It is often used colloquially in the moral sense of "goodness" or "rightness," but also refers to "proper procedure" or "correctness." We use the word for multiple meanings. Our goal is that Pono can be a useful tool for people to verify the _correctness_ of systems, which is surely the _right_ thing to do.



## Publications



* Makai Mann, Ahmed Irfan, Florian Lonsing, Yahan Yang, Hongce Zhang, Kristopher Brown, Aarti Gupta, Clark W. Barrett: [Pono: A Flexible and Extensible SMT-Based Model Checker](https://link.springer.com/chapter/10.1007/978-3-030-81688-9_22). CAV 2021.

  * Evaluated [software artifact](https://figshare.com/articles/software/CAV_2021_Artifact_Pono_Model_Checker/14479542).

* Makai Mann, Amalee Wilson, Yoni Zohar, Lindsey Stuntz, Ahmed Irfan, Kristopher Brown, Caleb Donovick, Allison Guman, Cesare Tinelli, Clark W. Barrett: [Smt-Switch: A Solver-Agnostic C++ API for SMT Solving](https://link.springer.com/chapter/10.1007/978-3-030-80223-3_26). SAT 2021.

* Makai Mann: [Augmenting transition systems for scalable symbolic model checking](https://searchworks.stanford.edu/view/13972018). PhD thesis, Stanford University, 2021.



## Awards



Pono was awarded the Oski Award under its original name _cosa2_ at [HWMCC'19](http://fmv.jku.at/hwmcc19/) for solving the largest number of benchmarks overall.



## Setup



* [optional] Install bison and flex

  * If you don't have bison and flex installed globally, run `./contrib/setup-bison.sh` and `./contrib/setup-flex.sh`

  * Even if you do have bison, you might get errors about not being able to load `-ly`. In such a case, run the bison setup script.

* Run `./contrib/setup-smt-switch.sh` -- it will build smt-switch with boolector

  * [optional] to build with MathSAT (required for interpolant-based model checking) you need to obtain the libraries yourself

    * note that MathSAT is under a custom non-BSD compliant license and you must assume all responsibility for meeting the conditions

    * download the solver from https://mathsat.fbk.eu/download.html, unpack it and rename the directory to `./deps/mathsat`

    * then add the `--with-msat` flag to the `setup-smt-switch.sh` command.

* Run `./contrib/setup-btor2tools.sh`.

* Run `./configure.sh`.

  * if building with mathsat, also include `--with-msat` as an option to `configure.sh`

* Run `cd build`.

* Run `make`.



### Dependencies



* Please see the [README of smt-switch](https://github.com/stanford-centaur/smt-switch#dependencies) for required dependencies.

* Note to Arch Linux users: building Pono will fail if the static library of [GMP](https://gmplib.org/), which is required by [cvc5](https://github.com/cvc5/cvc5/blob/main/INSTALL.rst), is not installed on your system. You can fix it by installing `libgmp-static` from [AUR](https://aur.archlinux.org/packages/libgmp-static).



### Profiling



We link against the [gperftools library](https://github.com/gperftools/gperftools)

to generate profiling data. To enable profiling, run `./configure.sh`

with flag `--with-profiling` and recompile Pono by running `make` in

the `build` directory. This assumes that you have installed the

gperftools library before, e.g., on Ubuntu, run `sudo apt-get install

google-perftools libgoogle-perftools-dev`.



To profile, run `./pono --profiling-log= ...` where

`` is the path to a file where profiling data is

written. After normal or abnormal (e.g. via sending a signal)

termination of Pono, the collected profile data can be analyzed by

running, e.g., `google-pprof --text ./pono ` to produce a

textual profile. See `man google-pprof` for further options.



In general, see

[https://github.com/gperftools/gperftools/tree/master/docs](https://github.com/gperftools/gperftools/tree/master/docs)

for further information about gperftools.



gperftools is licensed under a BSD 3-clause license, see

[https://github.com/gperftools/gperftools/blob/master/COPYING](https://github.com/gperftools/gperftools/blob/master/COPYING).



## Existing code



### Transition Systems

There are two Transition System interfaces:

* FunctionalTransitionSystem in fts.*

* TransitionSystem in rts.*



### Smt-Switch

[Smt-switch](https://github.com/stanford-centaur/smt-switch) is a C++ solver-agnostic API for SMT solvers. The main thing to remember is that everything is a pointer. Objects might be "typedef-ed" with `using` statements, but they're still `shared_ptr`s. Thus, when using a solver or a term, you need to use `->` accesses.



For more information, see the example usage in the [smt-switch tests](https://github.com/stanford-centaur/smt-switch/tree/master/tests/btor).

Other useful files to visit include:

* `smt-switch/include/solver.h`: this is the main interface you will be using

* `smt-switch/include/ops.h`: this contains all the ops you might need

  * Note: create indexed ops like `Op(Extract, 7, 4)`



## Python bindings

To build the `pono` python bindings, first make sure that you have [Cython](https://cython.org/) version >= 0.29 installed. Then ensure that `smt-switch` and its python bindings are installed. Finally, you can configure with `./configure.sh --python` and then build normally. The sequence of commands would be as follows:

```

# Optional recommended step: start a python virtualenv

# If you install in the virtualenv, you will need to activate it each time before using pono

# and deactivate the virtualenv with: deactivate

python3 -m venv env

source ./env/bin/activate

pip install Cython==0.29 pytest

./contrib/setup-smt-switch.sh --python

./contrib/setup-btor2tools.sh

pip install -e ./deps/smt-switch/build/python

./configure.sh --python

cd build

make -j4

pip install -e ./python

cd ../

# Test the bindings

pytest ./tests

```



## Generating BTOR2 from Verilog



The best tool for creating BTOR2 from Verilog is [Yosys](https://github.com/YosysHQ/yosys). Yosys has an excellent manual [here](http://www.clifford.at/yosys/files/yosys_manual.pdf). 

You can also run yosys interactively by running yosys with no arguments. Then you can view help messages for each command with: `help `. Running `help` with no arguments lists all commands.



A particularly useful command if you're having trouble is `show`, which can show the current state of the circuit in Yosys.



### Yosys Quick Start



Below is an example file with comments explaining each command that produces a BTOR2 file for [./samples/counter-false.v](./samples/counter-false.v). This should be enough for most use cases.



Once you have `yosys` installed, copy the text below into `gen-btor.ys` in the top-level of this repository. Then, running `yosys -s gen-btor.ys` will produce the BTOR2 file.



```

# read in the file(s) -- there can be multiple

# whitespace separated files, and you can

# escape new lines if necessary

read -formal ./samples/counter-false.v;



# prep does a conservative elaboration

# of the top module provided

prep -top counter;



# this command just does a sanity check

# of the hierarchy

hierarchy -check;



# If an assumption is flopped, you might

# see strange behavior at the last state

# (because the clock hasn't toggled)

# this command ensures that assumptions

# hold at every state

chformal -assume -early;



# this processes memories

# nomap means it will keep them as arrays

memory -nomap;



# flatten the design hierarchy

flatten;



# (optional) uncomment and set values to simulate reset signal

# use -resetn for an active low pin

# -n configures the number of cycles to simulate

# -rstlen configures how long the reset is active (recommended to keep it active for the whole simulation)

# -w tells it to write back the final state of the simulation as the initial state in the btor2 file

# another useful option is -zinit which zero initializes any uninitialized state

# sim -clock  -reset  -n  -rstlen  -w 



# (optional) use an "explicit" clock

# e.g. every state is a half cycle of the

# fastest clock

# use this option if you see errors that

# refer to "adff" or asynchronous components

# IMPORTANT NOTE: the clocks are not

# automatically toggled if you use this option

# clk2fflogic;



# This turns all undriven signals into

# inputs

setundef -undriven -expose;



# This writes to a file in BTOR2 format

write_btor counter-false.btor2

```