flow like the river

VISUALIZACION/node_modules/ngraph.forcelayout/lib/codeGenerators/generateQuadTree.js

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+const createPatternBuilder = require('./createPatternBuilder');
+const getVariableName = require('./getVariableName');
+
+module.exports = generateQuadTreeFunction;
+module.exports.generateQuadTreeFunctionBody = generateQuadTreeFunctionBody;
+
+// These exports are for InlineTransform tool.
+// InlineTransform: getInsertStackCode
+module.exports.getInsertStackCode = getInsertStackCode;
+// InlineTransform: getQuadNodeCode
+module.exports.getQuadNodeCode = getQuadNodeCode;
+// InlineTransform: isSamePosition
+module.exports.isSamePosition = isSamePosition;
+// InlineTransform: getChildBodyCode
+module.exports.getChildBodyCode = getChildBodyCode;
+// InlineTransform: setChildBodyCode
+module.exports.setChildBodyCode = setChildBodyCode;
+
+function generateQuadTreeFunction(dimension) {
+  let code = generateQuadTreeFunctionBody(dimension);
+  return (new Function(code))();
+}
+
+function generateQuadTreeFunctionBody(dimension) {
+  let pattern = createPatternBuilder(dimension);
+  let quadCount = Math.pow(2, dimension);
+
+  let code = `
+${getInsertStackCode()}
+${getQuadNodeCode(dimension)}
+${isSamePosition(dimension)}
+${getChildBodyCode(dimension)}
+${setChildBodyCode(dimension)}
+
+function createQuadTree(options, random) {
+  options = options || {};
+  options.gravity = typeof options.gravity === 'number' ? options.gravity : -1;
+  options.theta = typeof options.theta === 'number' ? options.theta : 0.8;
+
+  var gravity = options.gravity;
+  var updateQueue = [];
+  var insertStack = new InsertStack();
+  var theta = options.theta;
+
+  var nodesCache = [];
+  var currentInCache = 0;
+  var root = newNode();
+
+  return {
+    insertBodies: insertBodies,
+
+    /**
+     * Gets root node if it is present
+     */
+    getRoot: function() {
+      return root;
+    },
+
+    updateBodyForce: update,
+
+    options: function(newOptions) {
+      if (newOptions) {
+        if (typeof newOptions.gravity === 'number') {
+          gravity = newOptions.gravity;
+        }
+        if (typeof newOptions.theta === 'number') {
+          theta = newOptions.theta;
+        }
+
+        return this;
+      }
+
+      return {
+        gravity: gravity,
+        theta: theta
+      };
+    }
+  };
+
+  function newNode() {
+    // To avoid pressure on GC we reuse nodes.
+    var node = nodesCache[currentInCache];
+    if (node) {
+${assignQuads('      node.')}
+      node.body = null;
+      node.mass = ${pattern('node.mass_{var} = ', {join: ''})}0;
+      ${pattern('node.min_{var} = node.max_{var} = ', {join: ''})}0;
+    } else {
+      node = new QuadNode();
+      nodesCache[currentInCache] = node;
+    }
+
+    ++currentInCache;
+    return node;
+  }
+
+  function update(sourceBody) {
+    var queue = updateQueue;
+    var v;
+    ${pattern('var d{var};', {indent: 4})}
+    var r; 
+    ${pattern('var f{var} = 0;', {indent: 4})}
+    var queueLength = 1;
+    var shiftIdx = 0;
+    var pushIdx = 1;
+
+    queue[0] = root;
+
+    while (queueLength) {
+      var node = queue[shiftIdx];
+      var body = node.body;
+
+      queueLength -= 1;
+      shiftIdx += 1;
+      var differentBody = (body !== sourceBody);
+      if (body && differentBody) {
+        // If the current node is a leaf node (and it is not source body),
+        // calculate the force exerted by the current node on body, and add this
+        // amount to body's net force.
+        ${pattern('d{var} = body.pos.{var} - sourceBody.pos.{var};', {indent: 8})}
+        r = Math.sqrt(${pattern('d{var} * d{var}', {join: ' + '})});
+
+        if (r === 0) {
+          // Poor man's protection against zero distance.
+          ${pattern('d{var} = (random.nextDouble() - 0.5) / 50;', {indent: 10})}
+          r = Math.sqrt(${pattern('d{var} * d{var}', {join: ' + '})});
+        }
+
+        // This is standard gravitation force calculation but we divide
+        // by r^3 to save two operations when normalizing force vector.
+        v = gravity * body.mass * sourceBody.mass / (r * r * r);
+        ${pattern('f{var} += v * d{var};', {indent: 8})}
+      } else if (differentBody) {
+        // Otherwise, calculate the ratio s / r,  where s is the width of the region
+        // represented by the internal node, and r is the distance between the body
+        // and the node's center-of-mass
+        ${pattern('d{var} = node.mass_{var} / node.mass - sourceBody.pos.{var};', {indent: 8})}
+        r = Math.sqrt(${pattern('d{var} * d{var}', {join: ' + '})});
+
+        if (r === 0) {
+          // Sorry about code duplication. I don't want to create many functions
+          // right away. Just want to see performance first.
+          ${pattern('d{var} = (random.nextDouble() - 0.5) / 50;', {indent: 10})}
+          r = Math.sqrt(${pattern('d{var} * d{var}', {join: ' + '})});
+        }
+        // If s / r < θ, treat this internal node as a single body, and calculate the
+        // force it exerts on sourceBody, and add this amount to sourceBody's net force.
+        if ((node.max_${getVariableName(0)} - node.min_${getVariableName(0)}) / r < theta) {
+          // in the if statement above we consider node's width only
+          // because the region was made into square during tree creation.
+          // Thus there is no difference between using width or height.
+          v = gravity * node.mass * sourceBody.mass / (r * r * r);
+          ${pattern('f{var} += v * d{var};', {indent: 10})}
+        } else {
+          // Otherwise, run the procedure recursively on each of the current node's children.
+
+          // I intentionally unfolded this loop, to save several CPU cycles.
+${runRecursiveOnChildren()}
+        }
+      }
+    }
+
+    ${pattern('sourceBody.force.{var} += f{var};', {indent: 4})}
+  }
+
+  function insertBodies(bodies) {
+    ${pattern('var {var}min = Number.MAX_VALUE;', {indent: 4})}
+    ${pattern('var {var}max = Number.MIN_VALUE;', {indent: 4})}
+    var i = bodies.length;
+
+    // To reduce quad tree depth we are looking for exact bounding box of all particles.
+    while (i--) {
+      var pos = bodies[i].pos;
+      ${pattern('if (pos.{var} < {var}min) {var}min = pos.{var};', {indent: 6})}
+      ${pattern('if (pos.{var} > {var}max) {var}max = pos.{var};', {indent: 6})}
+    }
+
+    // Makes the bounds square.
+    var maxSideLength = -Infinity;
+    ${pattern('if ({var}max - {var}min > maxSideLength) maxSideLength = {var}max - {var}min ;', {indent: 4})}
+
+    currentInCache = 0;
+    root = newNode();
+    ${pattern('root.min_{var} = {var}min;', {indent: 4})}
+    ${pattern('root.max_{var} = {var}min + maxSideLength;', {indent: 4})}
+
+    i = bodies.length - 1;
+    if (i >= 0) {
+      root.body = bodies[i];
+    }
+    while (i--) {
+      insert(bodies[i], root);
+    }
+  }
+
+  function insert(newBody) {
+    insertStack.reset();
+    insertStack.push(root, newBody);
+
+    while (!insertStack.isEmpty()) {
+      var stackItem = insertStack.pop();
+      var node = stackItem.node;
+      var body = stackItem.body;
+
+      if (!node.body) {
+        // This is internal node. Update the total mass of the node and center-of-mass.
+        ${pattern('var {var} = body.pos.{var};', {indent: 8})}
+        node.mass += body.mass;
+        ${pattern('node.mass_{var} += body.mass * {var};', {indent: 8})}
+
+        // Recursively insert the body in the appropriate quadrant.
+        // But first find the appropriate quadrant.
+        var quadIdx = 0; // Assume we are in the 0's quad.
+        ${pattern('var min_{var} = node.min_{var};', {indent: 8})}
+        ${pattern('var max_{var} = (min_{var} + node.max_{var}) / 2;', {indent: 8})}
+
+${assignInsertionQuadIndex(8)}
+
+        var child = getChild(node, quadIdx);
+
+        if (!child) {
+          // The node is internal but this quadrant is not taken. Add
+          // subnode to it.
+          child = newNode();
+          ${pattern('child.min_{var} = min_{var};', {indent: 10})}
+          ${pattern('child.max_{var} = max_{var};', {indent: 10})}
+          child.body = body;
+
+          setChild(node, quadIdx, child);
+        } else {
+          // continue searching in this quadrant.
+          insertStack.push(child, body);
+        }
+      } else {
+        // We are trying to add to the leaf node.
+        // We have to convert current leaf into internal node
+        // and continue adding two nodes.
+        var oldBody = node.body;
+        node.body = null; // internal nodes do not cary bodies
+
+        if (isSamePosition(oldBody.pos, body.pos)) {
+          // Prevent infinite subdivision by bumping one node
+          // anywhere in this quadrant
+          var retriesCount = 3;
+          do {
+            var offset = random.nextDouble();
+            ${pattern('var d{var} = (node.max_{var} - node.min_{var}) * offset;', {indent: 12})}
+
+            ${pattern('oldBody.pos.{var} = node.min_{var} + d{var};', {indent: 12})}
+            retriesCount -= 1;
+            // Make sure we don't bump it out of the box. If we do, next iteration should fix it
+          } while (retriesCount > 0 && isSamePosition(oldBody.pos, body.pos));
+
+          if (retriesCount === 0 && isSamePosition(oldBody.pos, body.pos)) {
+            // This is very bad, we ran out of precision.
+            // if we do not return from the method we'll get into
+            // infinite loop here. So we sacrifice correctness of layout, and keep the app running
+            // Next layout iteration should get larger bounding box in the first step and fix this
+            return;
+          }
+        }
+        // Next iteration should subdivide node further.
+        insertStack.push(node, oldBody);
+        insertStack.push(node, body);
+      }
+    }
+  }
+}
+return createQuadTree;
+
+`;
+  return code;
+
+
+  function assignInsertionQuadIndex(indentCount) {
+    let insertionCode = [];
+    let indent = Array(indentCount + 1).join(' ');
+    for (let i = 0; i < dimension; ++i) {
+      insertionCode.push(indent + `if (${getVariableName(i)} > max_${getVariableName(i)}) {`);
+      insertionCode.push(indent + `  quadIdx = quadIdx + ${Math.pow(2, i)};`);
+      insertionCode.push(indent + `  min_${getVariableName(i)} = max_${getVariableName(i)};`);
+      insertionCode.push(indent + `  max_${getVariableName(i)} = node.max_${getVariableName(i)};`);
+      insertionCode.push(indent + `}`);
+    }
+    return insertionCode.join('\n');
+    // if (x > max_x) { // somewhere in the eastern part.
+    //   quadIdx = quadIdx + 1;
+    //   left = right;
+    //   right = node.right;
+    // }
+  }
+
+  function runRecursiveOnChildren() {
+    let indent = Array(11).join(' ');
+    let recursiveCode = [];
+    for (let i = 0; i < quadCount; ++i) {
+      recursiveCode.push(indent + `if (node.quad${i}) {`);
+      recursiveCode.push(indent + `  queue[pushIdx] = node.quad${i};`);
+      recursiveCode.push(indent + `  queueLength += 1;`);
+      recursiveCode.push(indent + `  pushIdx += 1;`);
+      recursiveCode.push(indent + `}`);
+    }
+    return recursiveCode.join('\n');
+    // if (node.quad0) {
+    //   queue[pushIdx] = node.quad0;
+    //   queueLength += 1;
+    //   pushIdx += 1;
+    // }
+  }
+
+  function assignQuads(indent) {
+    // this.quad0 = null;
+    // this.quad1 = null;
+    // this.quad2 = null;
+    // this.quad3 = null;
+    let quads = [];
+    for (let i = 0; i < quadCount; ++i) {
+      quads.push(`${indent}quad${i} = null;`);
+    }
+    return quads.join('\n');
+  }
+}
+
+function isSamePosition(dimension) {
+  let pattern = createPatternBuilder(dimension);
+  return `
+  function isSamePosition(point1, point2) {
+    ${pattern('var d{var} = Math.abs(point1.{var} - point2.{var});', {indent: 2})}
+  
+    return ${pattern('d{var} < 1e-8', {join: ' && '})};
+  }  
+`;
+}
+
+function setChildBodyCode(dimension) {
+  var quadCount = Math.pow(2, dimension);
+  return `
+function setChild(node, idx, child) {
+  ${setChildBody()}
+}`;
+  function setChildBody() {
+    let childBody = [];
+    for (let i = 0; i < quadCount; ++i) {
+      let prefix = (i === 0) ? '  ' : '  else ';
+      childBody.push(`${prefix}if (idx === ${i}) node.quad${i} = child;`);
+    }
+
+    return childBody.join('\n');
+    // if (idx === 0) node.quad0 = child;
+    // else if (idx === 1) node.quad1 = child;
+    // else if (idx === 2) node.quad2 = child;
+    // else if (idx === 3) node.quad3 = child;
+  }
+}
+
+function getChildBodyCode(dimension) {
+  return `function getChild(node, idx) {
+${getChildBody()}
+  return null;
+}`;
+
+  function getChildBody() {
+    let childBody = [];
+    let quadCount = Math.pow(2, dimension);
+    for (let i = 0; i < quadCount; ++i) {
+      childBody.push(`  if (idx === ${i}) return node.quad${i};`);
+    }
+
+    return childBody.join('\n');
+    // if (idx === 0) return node.quad0;
+    // if (idx === 1) return node.quad1;
+    // if (idx === 2) return node.quad2;
+    // if (idx === 3) return node.quad3;
+  }
+}
+
+function getQuadNodeCode(dimension) {
+  let pattern = createPatternBuilder(dimension);
+  let quadCount = Math.pow(2, dimension);
+  var quadNodeCode = `
+function QuadNode() {
+  // body stored inside this node. In quad tree only leaf nodes (by construction)
+  // contain bodies:
+  this.body = null;
+
+  // Child nodes are stored in quads. Each quad is presented by number:
+  // 0 | 1
+  // -----
+  // 2 | 3
+${assignQuads('  this.')}
+
+  // Total mass of current node
+  this.mass = 0;
+
+  // Center of mass coordinates
+  ${pattern('this.mass_{var} = 0;', {indent: 2})}
+
+  // bounding box coordinates
+  ${pattern('this.min_{var} = 0;', {indent: 2})}
+  ${pattern('this.max_{var} = 0;', {indent: 2})}
+}
+`;
+  return quadNodeCode;
+
+  function assignQuads(indent) {
+    // this.quad0 = null;
+    // this.quad1 = null;
+    // this.quad2 = null;
+    // this.quad3 = null;
+    let quads = [];
+    for (let i = 0; i < quadCount; ++i) {
+      quads.push(`${indent}quad${i} = null;`);
+    }
+    return quads.join('\n');
+  }
+}
+
+function getInsertStackCode() {
+  return `
+/**
+ * Our implementation 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 pressure: 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
+}
+`;
+}