From 6a6d433cbed63f83924d5f03810a211a501618d0 Mon Sep 17 00:00:00 2001
From: Yi Wang <yiwang01@baidu.com>
Date: Thu, 7 Dec 2017 16:36:14 -0800
Subject: [PATCH] Update block parent-kid relationship

---
 doc/design/concurrent_programming.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/doc/design/concurrent_programming.md b/doc/design/concurrent_programming.md
index 0fd37bd697..afc65e831d 100644
--- a/doc/design/concurrent_programming.md
+++ b/doc/design/concurrent_programming.md
@@ -83,6 +83,7 @@ message ProgramDesc {
   }
   
   block[1] = Block {
+    parent = 0,
     vars = [x, y, index],
     ops = [
       slice(input = [X, index], output = x) # index is initialized by parallel_for
@@ -121,6 +122,7 @@ An explanation of the above program:
   2. creates `len(L)` threads by calling into the `ThreadPool` singleton, each thread  
      1. creates an Executor instance, and
      2. calls `Executor.Run(block)`, where `block` is block 1 as explained above.
+1. Please be aware that block 1 is a sub-block of block 0, so ops in block 1 could refer to variables defined in block 0.
 
 ### The Worker Program
 
-- 
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