有关tensorflow分布式训练示例的问题

我正在研究分布式tensorflow示例：tensorflow distributed training code template这是一个 between-graph 副本和 asynchronous 训练示例模板 .

我还发现了以下代码示例，它遵循相同的方式（ between-graph, asynchronous ） . 此示例来自murry's answer . 我在下面粘贴它以帮助我表达我的问题：

1，在这个例子中，假设我有两个工作任务和两个ps任务，所有变量： hid_w,hid_b,sm_w,sm_b... 是否放在参数服务器（ps）设备上？如果是，则展示位置是否遵循循环方式（ hid_w 至 ps/task:0 ， hid_b 至 ps/task:1 ， sm_w 至 ps/task:0 ， sm_b 至 ps/task:1 ....）

2，如果我想实现 synchronous replicated training ，我可以使用 tf.train.SyncReplicasOptimizer 作为包装器 . 但是， tf.train.SyncReplicasOptimizer 只能包含基于 Optimizer 的梯度下降，例如 tf.train.AdagradOptimizer 和 tf.train.GradientDescentOptimizer . 我的问题是 how to achieve synchronous training of algorithm like K-means that does not use any Optimizer? ;没有任何方法可以实现同步培训 tf.train.SyncReplicasOptimizer

import tensorflow as tf
from tensorflow.examples.tutorials.mnist import input_data

# Flags for defining the tf.train.ClusterSpec
tf.app.flags.DEFINE_string("ps_hosts", "",
                           "Comma-separated list of hostname:port pairs")
tf.app.flags.DEFINE_string("worker_hosts", "",
                           "Comma-separated list of hostname:port pairs")

# Flags for defining the tf.train.Server
tf.app.flags.DEFINE_string("job_name", "", "One of 'ps', 'worker'")
tf.app.flags.DEFINE_integer("task_index", 0, "Index of task within the job")

FLAGS = tf.app.flags.FLAGS


def main(_):
  ps_hosts = FLAGS.ps_hosts.split(",")
  worker_hosts = FLAGS.worker_hosts.split(",")

  # Create a cluster from the parameter server and worker hosts.
  cluster = tf.train.ClusterSpec({"ps": ps_hosts, "worker": worker_hosts})

  # Create and start a server for the local task.
  server = tf.train.Server(cluster,
                           job_name=FLAGS.job_name,
                           task_index=FLAGS.task_index)

  if FLAGS.job_name == "ps":
    server.join()
  elif FLAGS.job_name == "worker":

    # Assigns ops to the local worker by default.
    with tf.device(tf.train.replica_device_setter(
        worker_device="/job:worker/task:%d" % FLAGS.task_index,
        cluster=cluster)):



      # Variables of the hidden layer
      hid_w = tf.Variable(
          tf.truncated_normal([IMAGE_PIXELS * IMAGE_PIXELS, FLAGS.hidden_units],
                              stddev=1.0 / IMAGE_PIXELS), name="hid_w")
      hid_b = tf.Variable(tf.zeros([FLAGS.hidden_units]), name="hid_b")

      # Variables of the softmax layer
      sm_w = tf.Variable(
          tf.truncated_normal([FLAGS.hidden_units, 10],
                              stddev=1.0 / math.sqrt(FLAGS.hidden_units)),
          name="sm_w")
      sm_b = tf.Variable(tf.zeros([10]), name="sm_b")

      x = tf.placeholder(tf.float32, [None, IMAGE_PIXELS * IMAGE_PIXELS])
      y_ = tf.placeholder(tf.float32, [None, 10])

      hid_lin = tf.nn.xw_plus_b(x, hid_w, hid_b)
      hid = tf.nn.relu(hid_lin)

      y = tf.nn.softmax(tf.nn.xw_plus_b(hid, sm_w, sm_b))
      loss = -tf.reduce_sum(y_ * tf.log(tf.clip_by_value(y, 1e-10, 1.0)))

      global_step = tf.Variable(0)

      train_op = tf.train.AdagradOptimizer(0.01).minimize(
          loss, global_step=global_step)

      saver = tf.train.Saver()
      summary_op = tf.merge_all_summaries()
      init_op = tf.initialize_all_variables()

    # Create a "supervisor", which oversees the training process.
    sv = tf.train.Supervisor(is_chief=(FLAGS.task_index == 0),
                             logdir="/tmp/train_logs",
                             init_op=init_op,
                             summary_op=summary_op,
                             saver=saver,
                             global_step=global_step,
                             save_model_secs=600)

    mnist = input_data.read_data_sets(FLAGS.data_dir, one_hot=True)

    # The supervisor takes care of session initialization, restoring from
    # a checkpoint, and closing when done or an error occurs.
    with sv.managed_session(server.target) as sess:
      # Loop until the supervisor shuts down or 1000000 steps have completed.
      step = 0
      while not sv.should_stop() and step < 1000000:
        # Run a training step asynchronously.
        # See `tf.train.SyncReplicasOptimizer` for additional details on how to
        # perform *synchronous* training.

        batch_xs, batch_ys = mnist.train.next_batch(FLAGS.batch_size)
        train_feed = {x: batch_xs, y_: batch_ys}

        _, step = sess.run([train_op, global_step], feed_dict=train_feed)

    # Ask for all the services to stop.
    sv.stop()

if __name__ == "__main__":
  tf.app.run()