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https://github.com/shnarazk/mios

A SAT solver written in Haskell.
https://github.com/shnarazk/mios

haskell sat-solver

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A SAT solver written in Haskell.

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# Mios -- Minisat-based Implementation and Optimization Study
----

`Mios` is yet another minisat-based SAT solver implementation in Haskell, as
a part of my research theme.

- [ChangeLog](ChangeLog.md)

### > Features

* fundamentally it is developed based on Minisat-1.14 and 2.2.0.
* Firstly, version 1.0 was based on N. Een and N. Sorensson, *“An extensible SAT-solver [extended version 1.2],”* in 6th Int. Conf. on Theory and Applications of Satisfiability Testing (SAT2003), 2003, pp. 502–518.
* Version 1.1 was a *line-to-line* translation of [MiniSat 1.14](http://minisat.se/downloads/MiniSat_v1.14.2006-Aug-29.src.zip).
* Version 1.2 imported some idea used in Glucose 4.0.
* Version 1.5 uses Literal Block Distance (LBD).
* Version 1.6 adopts new ideas: EMA, ACIDS and so on.
* runs in `IO` monad, uses `Data.Primitive.ByteArray` mainly and `reallyUnsafePtrEquality`.
* very fast, compared with other SAT solvers written in Haskell; see below.

#### benchmark results

- SAT-Competition 2017 Main track, running 3 jobs *in parallel* with a 510 second timeout on Intel Core i7-3930K @ 12x 3.8GHz
(Therefore results near the threshold should be affected by other threads more or less.)

![Cactus plot with Mios-1.6.1: SAT Competition 2017 main](https://shujinarazaki.gitlab.io/pages/images/mios-1.6.1.png)

### > Install

##### Requirements

- ghc-8.0.1 or upper (By deleting `default-extensions` from mios.cabal, you can use ghc-7.10.x.)
- [Stack](http://www.haskellstack.org/)
- If you want to build with cabal, please use the cabal file under utils directory.

##### Stack

```
git clone https://github.com/shnarazk/mios
stack init --resolver lts-11.X # for ghc-8.2.X
stack install
```

##### Hackage/Cabal

Mios is registered in [hackage](http://hackage.haskell.org/package/mios) now.

```
cabal install mios
```

### > Usage

##### * As a standalone program

```
$ mios a.cnf
an assignment :: [Int]

$ mios --help
mios 1.6.1 https://github.com/shnarazk/mios/
Usage: mios [OPTIONS] target.cnf
-d 0.95 --variable-decay-rate=0.95 [solver] variable activity decay rate (0.0 - 1.0)
-c 0.999 --clause-decay-rate=0.999 [solver] clause activity decay rate (0.0 - 1.0)
--Rb=1.2 [solver] expansion rate for blocking restart (>= 1.0)
--Rf=1.01 [solver] expansion rate for forcing restart (>= 1.0)
--Rs=100.0 [solver] a fixed number of conflicts between restarts
-: --validate-assignment [solver] read an assignment from STDIN and validate it
--validate [solver] self-check (satisfiable) assignment
-o file --output=file [option] filename to store result
-v --verbose [option] display misc information
-X --hide-solution [option] hide solution
--benchmark=-1/0/N [devel] No/Exhaustive/N-second timeout benchmark
--sequence=NUM [devel] set 2nd field of a CSV generated by benchmark
--dump=0 [devel] dump level; 1:solved, 2:reduction, 3:restart
-h --help [misc] display this message
--version [misc] display program ID
```

If you have GNU parallel, Mios works well with it:

```
parallel "mios --benchmark=0 --sequence={#} -o {.cnf}.result {}" ::: *.cnf
```

##### * In Haskell

```haskell
module Main where -- this is sample.hs in app/
import SAT.Mios (CNFDescription (..), solveSAT)

clauses = [[1, 2], [1, 3], [-1, -2], [1, -2, 3], [-3]] :: [[Int]]
desc = CNFDescription 3 5 Nothing -- #vars, #clauses, Just pathname or Nothing

main = do
asg <- solveSAT desc clauses -- solveSAT :: Traversable m => CNFDescription -> m [Int] -> IO [Int]
putStrLn $ if null asg then "unsatisfiable" else show asg
```

```
$ stack ghc app/sample.hs
$ app/sample
[1,-2,-3]
```

Of course, you can use Mios in ghci similarly.

```
$ stack ghci
...>
```