javascript-lp-solver/src/Tableau/branchingStrategies.js

Easy to use, JSON oriented Linear Programming and Mixed Int. Programming Solver

/*global require*/
var Tableau = require("./Tableau.js");

function VariableData(index, value) {
    this.index = index;
    this.value = value;
}

//-------------------------------------------------------------------
//-------------------------------------------------------------------
Tableau.prototype.getMostFractionalVar = function () {
    var biggestFraction = 0;
    var selectedVarIndex = null;
    var selectedVarValue = null;
    var mid = 0.5;

    var integerVariables = this.model.integerVariables;
    var nIntegerVars = integerVariables.length;
    for (var v = 0; v < nIntegerVars; v++) {
        var varIndex = integerVariables[v].index;
        var varRow = this.rowByVarIndex[varIndex];
        if (varRow === -1) {
            continue;
        }

        var varValue = this.matrix[varRow][this.rhsColumn];
        var fraction = Math.abs(varValue - Math.round(varValue));
        if (biggestFraction < fraction) {
            biggestFraction = fraction;
            selectedVarIndex = varIndex;
            selectedVarValue = varValue;
        }
    }

    return new VariableData(selectedVarIndex, selectedVarValue);
};

//-------------------------------------------------------------------
//-------------------------------------------------------------------
Tableau.prototype.getFractionalVarWithLowestCost = function () {
    var highestCost = Infinity;
    var selectedVarIndex = null;
    var selectedVarValue = null;

    var integerVariables = this.model.integerVariables;
    var nIntegerVars = integerVariables.length;
    for (var v = 0; v < nIntegerVars; v++) {
        var variable = integerVariables[v];
        var varIndex = variable.index;
        var varRow = this.rowByVarIndex[varIndex];
        if (varRow === -1) {
            // Variable value is non basic
            // its value is 0
            continue;
        }

        var varValue = this.matrix[varRow][this.rhsColumn];
        if (Math.abs(varValue - Math.round(varValue)) > this.precision) {
            var cost = variable.cost;
            if (highestCost > cost) {
                highestCost = cost;
                selectedVarIndex = varIndex;
                selectedVarValue = varValue;
            }
        }
    }

    return new VariableData(selectedVarIndex, selectedVarValue);
};