binary-decision-diagram

binary decision diagram

A library to create, minimize and optimize binary decision diagrams in JavaScript.

A binary decision diagram is a data structure that represents a set of boolean function in an efficient way. To learn more about it, follow these links:

• Introduction on BDDs
• Presentation on BDDs
• Implementation of ROBDD

Installation

npm install binary-decision-diagram --save

createBddFromTruthTable()

Creates a BDD from a truth table. The Truth-Table is a Map<string, number> where the string is a truth-set like 1101 and the number is the value.

const truthTable = new Map();
truthTable.add('00', 1);
truthTable.add('01', 3);
truthTable.add('10', 2);
truthTable.add('11', 1);

const bdd = createBddFromTruthTable(
    truthTable
);

minimize()

Reduces the nodes of a BDD by applying the reduction- and elimination rules.

bdd.minimize(
    false // if true, logs stuff (optional)
);

countNodes()

Returns the amount of nodes of the BDD.

bdd.countNodes(); // returns a number

removeIrrelevantLeafNodes()

Removes all irrelevant leaf-nodes with the given value.

// this will remove all leaf-nodes with the value of 5
bdd.removeIrrelevantLeafNodes(5);

resolve()

Resolves a state by calling the boolean functions through the nodes.

The resolve-functions is an object with the truth-table-value as key and a boolean function as value.

const resolvers: ResolverFunctions = {
    1: (i) => true,
    2: (i) => true,
    3: (i) => false
};

const bddValue = bdd.resolve(
    resolvers, 
    i // input that is passed to the resolvers
); // returns a value from the truth table

bddToMinimalString()

Returns a string-representation of the BDD which can be used in the client side to have a small javascript-bundle. BDDs can be very big so an effective storage format was needed.

const minimalString = bddToMinimalString(bdd)

minimalStringToSimpleBdd()

Parses the minimal string into an SimpleBdd. The SimpleBdd very small and only can resolve stuff.

const simpleBdd = minimalStringToSimpleBdd(str);

resolveWithMinimalBdd()

Resolves a value with the SimpleBdd and the ResolverFunctions.

resolveWithSimpleBdd(
    simpleBdd,
    resolvers,
    key
);

optimizeBruteForce()

Optimizes the sorting of the boolean functions to get an optimal BDD. Returns a promise with the best found BDD.

const optimizedResult = await optimizeBruteForce({
    truthTable,
    iterations: 10000,
    // hook that runs whenever a bdd is created (optional)
    afterBddCreation: (bdd: RootNode) => {
        bdd.removeIrrelevantLeafNodes(unknownValueActionId);
    },
    // hook that is triggered whenever a better bdd was found (optional)
    onBetterBdd: (res: OptimisationResult) => {
        const bddMinimalString = bddToMinimalString(res.bdd);
        console.log('new string: ' + bddMinimalString);
        console.log('value mapping:');
        console.dir(res.mapping);
    },
    // (optional) start with this BDD to optimize. If not set, will create an own one.
    initialBdd: myBdd
});