https://github.com/catoverflow/robdd
All-in-one proposition to ROBDD constructor, featured by LALR parsing
https://github.com/catoverflow/robdd
robdd sat-solver
Last synced: 11 months ago
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All-in-one proposition to ROBDD constructor, featured by LALR parsing
- Host: GitHub
- URL: https://github.com/catoverflow/robdd
- Owner: Catoverflow
- License: mit
- Created: 2022-06-19T07:26:10.000Z (almost 4 years ago)
- Default Branch: main
- Last Pushed: 2025-04-01T22:31:03.000Z (about 1 year ago)
- Last Synced: 2025-04-01T23:28:55.544Z (about 1 year ago)
- Topics: robdd, sat-solver
- Language: C++
- Homepage:
- Size: 241 KB
- Stars: 6
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# ROBDD Constructor
**An ROBDD constructor and SAT/unSAT solver** written in C++, featured by **LALR** parsing
Implemented as class project, shared with love
## Requirement
`flex`, `bison` for ROBDD frontend, `graphviz` for image generating.
~~~~mermaid
flowchart LR
subgraph Frontend
Flex--"lexical symbol"-->Bison
end
subgraph Backend
ROBDD
end
subgraph Visualization
Graphviz
end
Bison<--"construct & reduce\nby LALR"-->ROBDD
ROBDD--"format &\noutput"-->Graphviz
~~~~
## Usage
`make ROBDD` compile to binary first.
~~~~
Usage: ROBDD [-SscAa] [-o filename]
-S - Check if the proposition is All-SAT
-s - Check if the proposition is Any-SAT
-A - Construct ROBDD under fixed ASCII order,
smallest variable at top
-a (default) - Construct ROBDD under parsing order
-c - Return SAT count for the proposition
-t - Return ROBDD construction time cost
-o filename - Print ROBDD to filename.svg
~~~~
*Note: `-a` is a heuristic approach, `-A` may result in over-sized ROBDD*
Input your proposition then.
## Syntax
### Variable
For BDD, we take every variables as bool variables, which means they only take 0 or 1 as assignment. Each variable must start with letter (uppercase or lowercase), and can be a mixture of digits of letter, as regex `[a-zA-Z]+[0-9]*` suggests.
### Operator
| Symbol | Corresponding operation | Example | Priority |
| ------ | ----------------------- | ------------------------------ | -------- |
| `~` | $\neg$ not | `~a` for $\neg a$ | 1 |
| `&` | $\wedge$ and | `a&b` for $a\wedge b$ | 2 |
| `\|` | $\vee$ or | `a\|b` for $a\wedge b$ | 2 |
| `=` | $\leftrightarrow$ xnor | `a=b` for $a\leftrightarrow b$ | 2 |
| `!=` | $\neq$ xor | `a!=b` for $a\neq b$ | 2 |
| `->` | $\rightarrow$ infer | `a->b` for $a\rightarrow b$ | 3 |
| `()` | pair of parentheses | `(some formula here)` | 0 |
Smaller number means higher priority.
A valid proposition for example: `Aa&B->C0|h`
## N Queens
There is a script `n_queens_test/nqueens.py`, you can use its output as `ROBDD`'s input to test its correctness:
~~~~bash
python n_queens_test/nqueens.py 6 | ./ROBDD -Ssc
~~~~
Or print the output, an example is as below, for n > 6, visualization will take a long time.
__6 queens__
## Todo
- Short Term
Move print module to visitor pattern, uncouple ROBDD from extensions
- Long Term
Use Bison C++ APIs, introduce `std::shared_ptr` for auto pruning
## Credits
Henrik Reif Andersen, who wrote *[An Introduction to Binary Decision Diagrams](https://www.cs.utexas.edu/~isil/cs389L/bdd.pdf)* and it's my major reference.