From 6b762f65192ae8a3c35a9a01a1719c3e9402225f Mon Sep 17 00:00:00 2001
From: Xin Pan <panxin.grad@gmail.com>
Date: Tue, 15 Jan 2019 15:52:39 +0800
Subject: [PATCH] add doc

test=develop
---
 paddle/fluid/imperative/README.md | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/paddle/fluid/imperative/README.md b/paddle/fluid/imperative/README.md
index c23a779048..4c4d619b35 100644
--- a/paddle/fluid/imperative/README.md
+++ b/paddle/fluid/imperative/README.md
@@ -91,7 +91,7 @@ class Tracer {
 ```
 
 * Trace forward operations
-* Perform simple python level infer and return to user.
+* Perform quick shape/type infer, push kernel execution engine and return to user.
 * Perform autograd to generate gradients.
 * Clear trace.
 * Apply gradients with optimizers
@@ -113,6 +113,20 @@ when needed.
 
 Lazy execution of pushed C++ operations.
 
+## Device Placement
+
+* Operator executes on the inputs' device.
+* All inputs should live on the same device.
+* use `Var.to()` to explicitly move var to a device.
+
+## Save/Load Models
+
+TODO
+
+## I/O
+
+TODO
+
 ## Refactor
 
 * All function layers with parameters converted to class Layers.
@@ -181,15 +195,6 @@ class MLP(fluid.imperative.Layer):
      out._backward()
 ```
 
-
-## Save/Load Models
-
-TODO
-
-## I/O
-
-TODO
-
 # Plan
 
 2.1，3 fulltime, Can run a few simple models. (Currently, 2 20% engs)
-- 
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