From 4da48edb2b3b7d56ad154f667dc05bcd1bf7390a Mon Sep 17 00:00:00 2001
From: Leon Chen <leon@md.ai>
Date: Mon, 19 Sep 2016 11:36:58 -0400
Subject: [PATCH] add comments to Model traverseDAG generator function

---
 src/Model.js | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/Model.js b/src/Model.js
index a0615d0..3716267 100644
--- a/src/Model.js
+++ b/src/Model.js
@@ -249,8 +249,17 @@ export default class Model {
    */
   * traverseDAG (nodes) {
     if (nodes.length === 0) {
+      // Stopping criterion:
+      // an output node will have 0 outbound nodes.
       return true
     } else if (nodes.length === 1) {
+      // Where computational logic lives for a given layer node
+      // - Makes sure results are available from inbound layer nodes
+      // - Keeps generator going until results are available from inbound layer nodes
+      //   (important for Merge layer nodes where multiple inbound nodes may
+      //    complete asynchronously)
+      // - Runs computation for current layer node: .call()
+      // - Starts new generator function for outbound nodes
       const node = nodes[0]
       const { layerClass, inbound, outbound } = this.modelDAG[node]
       if (layerClass !== 'Input') {