ngraph.quadtreebh/insertStack.js

Quad tree data structure for Barnes-Hut simulation

module.exports = InsertStack;

/**
 * Our implmentation of QuadTree is non-recursive to avoid GC hit
 * This data structure represent stack of elements
 * which we are trying to insert into quad tree.
 */
function InsertStack () {
    this.stack = [];
    this.popIdx = 0;
}

InsertStack.prototype = {
    isEmpty: function() {
        return this.popIdx === 0;
    },
    push: function (node, body) {
        var item = this.stack[this.popIdx];
        if (!item) {
            // we are trying to avoid memory pressue: create new element
            // only when absolutely necessary
            this.stack[this.popIdx] = new InsertStackElement(node, body);
        } else {
            item.node = node;
            item.body = body;
        }
        ++this.popIdx;
    },
    pop: function () {
        if (this.popIdx > 0) {
            return this.stack[--this.popIdx];
        }
    },
    reset: function () {
        this.popIdx = 0;
    }
};

function InsertStackElement(node, body) {
    this.node = node; // QuadTree node
    this.body = body; // physical body which needs to be inserted to node
}