CODEWITHSUNDEEP
tensorflow
Pek
Pek

Reputation: 166

Tensorflow: how to create a local variable?

I'm trying to understand how local and global variables are different in tensorflow and what's the right way to initialize the variables.

According to the doc, tf.local_variables_initializer:

Returns an Op that initializes all local variables.

This is just a shortcut for variables_initializer(local_variables())

So the essential part is tf.local_variables. The doc:

Local variables - per process variables, usually not saved/restored to checkpoint and used for temporary or intermediate values. For example, they can be used as counters for metrics computation or number of epochs this machine has read data.

It sounds logical, however, no matter how I tried, I couldn't make any variable local. 

features = 2
hidden = 3

with tf.variable_scope('start'):
  x = tf.placeholder(tf.float32, shape=[None, features], name='x')
  y = tf.placeholder(tf.float32, shape=[None], name='y')

with tf.variable_scope('linear'):
  W = tf.get_variable(name='W', shape=[features, hidden])
  b = tf.get_variable(name='b', shape=[hidden], initializer=tf.zeros_initializer)
  z = tf.matmul(x, W) + b

with tf.variable_scope('optimizer'):
  predict = tf.reduce_sum(z, axis=1)
  loss = tf.reduce_mean(tf.square(y - predict))
  optimizer = tf.train.AdamOptimizer(0.1).minimize(loss)

print(tf.local_variables())

The output is always an empty list. How and should I create local variables?

Upvotes: 1

Views: 620

Answers (2)

Pek
Pek

Reputation: 166

Think I found it. The magic addition to make a variable local is collections=[tf.GraphKeys.LOCAL_VARIABLES] in tf.get_variable. So this way W becomes are local variable:

W = tf.get_variable(name='W', shape=[features, hidden], collections=[tf.GraphKeys.LOCAL_VARIABLES])

The documentation mentions one more possibility that also works:

q = tf.contrib.framework.local_variable(0.0, name='q')

Upvotes: 1

nessuno
nessuno

Reputation: 27042

A local variable is just a regular variable that's added to a "special" collection.

The collection is tf.GraphKeys.LOCAL_VARIABLES.

You can pick any variable definition and just add the parameter collections=[tf.GraphKeys.LOCAL_VARIABLES] to add the variable to the specified collection list.

Upvotes: 1

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