ngraph.path/a-star/makeSearchStatePool.js

/**
 * This class represents a single search node in the exploration tree for
 * A* algorithm.
 * 
 * @param {Object} node  original node in the graph
 */
function NodeSearchState(node) {
  this.node = node;

  // How we came to this node?
  this.parent = null;

  this.closed = false;
  this.open = 0;

  this.distanceToSource = Number.POSITIVE_INFINITY;
  // the f(n) = g(n) + h(n) value
  this.fScore = Number.POSITIVE_INFINITY;

  // used to reconstruct heap when fScore is updated.
  this.heapIndex = -1;
};

export default function makeSearchStatePool() {
  var currentInCache = 0;
  var nodeCache = [];

  return {
    createNewState: createNewState,
    reset: reset
  };

  function reset() {
    currentInCache = 0;
  }

  function createNewState(node) {
    var cached = nodeCache[currentInCache];
    if (cached) {
      // TODO: This almost duplicates constructor code. Not sure if
      // it would impact performance if I move this code into a function
      cached.node = node;
      // How we came to this node?
      cached.parent = null;

      cached.closed = false;
      cached.open = 0;

      cached.distanceToSource = Number.POSITIVE_INFINITY;
      // the f(n) = g(n) + h(n) value
      cached.fScore = Number.POSITIVE_INFINITY;

      // used to reconstruct heap when fScore is updated.
      cached.heapIndex = -1;

    } else {
      cached = new NodeSearchState(node);
      nodeCache[currentInCache] = cached;
    }
    currentInCache++;
    return cached;
  }
}