[Docs] Add English document for AdamW Optimizer. (DeepRec-AI#654)

docs/docs_en/AdamW-Optimizer.md

@@ -0,0 +1,54 @@
+# AdamW Optimizer
+## Introduction
+The AdamW optimizer supports EmbeddingVariable, which adds the weight decay function compared to the Adam optimizer.
+
+This is a kind of implementation of the AdamW optimizer which is mentioned in Loshch ilov & Hutter (https://arxiv.org/abs/1711.05101) "Decoupled Weight Decay Regularization".
+
+## User interface
+You need to use the `tf.train.AdamWOptimizer` function interface during training, which is the same as other TF native Optimizers. The specific definition is as follows:
+```python
+class AdamWOptimizer(DecoupledWeightDecayExtension, adam.AdamOptimizer):
+  def __init__(self,
+               weight_decay,
+               learning_rate=0.001,
+               beta1=0.9,
+               beta2=0.999,
+               epsilon=1e-8,
+               use_locking=False,
+               name="AdamW"):
+
+# call function
+optimizer = tf.train.AdamWOptimizer(
+               weight_decay=weight_decay_new
+               learning_rate=learning_rate_new,
+               beta1=0.9,
+               beta2=0.999,
+               epsilon=1e-8)
+```
+## Example
+```python
+import tensorflow as tf
+
+var = tf.get_variable("var_0", shape=[10,16],
+                       initializer=tf.ones_initializer(tf.float32))
+
+emb = tf.nn.embedding_lookup(var, tf.cast([0,1,2,5,6,7], tf.int64))
+fun = tf.multiply(emb, 2.0, name='multiply')
+loss = tf.reduce_sum(fun, name='reduce_sum')
+
+gs= tf.train.get_or_create_global_step()
+opt = tf.train.AdamWOptimizer(weight_decay=0.01, learning_rate=0.1)
+
+g_v = opt.compute_gradients(loss)
+train_op = opt.apply_gradients(g_v)
+
+init = tf.global_variables_initializer()
+
+sess_config = tf.ConfigProto(allow_soft_placement=True, log_device_placement=False)
+with tf.Session(config=sess_config) as sess:
+  sess.run([init])
+  print(sess.run([emb, train_op, loss]))
+  print(sess.run([emb, train_op, loss]))
+  print(sess.run([emb, train_op, loss]))
+```
+

docs/docs_en/index.md

@@ -60,6 +60,7 @@ GPU-MultiStream
 :caption: Optimizer
 
 AdamAsync-Optimizer
+AdamW-Optimizer
 ```
 
 ```{toctree}