pg8.py

# -*- coding: utf-8 -*-
# @Author: Zedong Peng
# @Date:   2019-06-29 00:46:35
# @Last Modified by:   Zedong Peng
# @Last Modified time: 2019-06-29 22:58:27

import numpy as np
import tensorflow as tf
import gym
import logz
import os
import time
import inspect
from multiprocessing import Process
from supply_distribution8 import SupplyDistribution
import pandas as pd

#============================================================================================#
# Utilities
#============================================================================================#


def build_mlp(input_placeholder, output_size, scope, n_layers, size, activation=tf.tanh, output_activation=None):
    """
        Builds a feedforward neural network

        arguments:
            input_placeholder: placeholder variable for the state (batch_size, input_size)
            output_size: size of the output layer
            scope: variable scope of the network
            n_layers: number of hidden layers
            size: dimension of the hidden layer
            activation: activation of the hidden layers
            output_activation: activation of the ouput layers

        returns:
            output placeholder of the network (the result of a forward pass) 

        Hint: use tf.layers.dense    
    """
    with tf.variable_scope(scope):
        layer = input_placeholder
        for i in range(n_layers):
            layer = tf.layers.dense(
                inputs=layer, units=size, activation=activation)
        output_placeholder = tf.layers.dense(
            inputs=layer, units=output_size, activation=output_activation)
    return output_placeholder


def pathlength(path):
    return len(path["reward"])


def setup_logger(logdir, locals_):
    # Configure output directory for logging
    logz.configure_output_dir(logdir)
    # Log experimental parameters
    args = inspect.getargspec(train_PG)[0]
    params = {k: locals_[k] if k in locals_ else None for k in args}
    logz.save_params(params)

#============================================================================================#
# Policy Gradient
#============================================================================================#


class Agent(object):

    def __init__(self, computation_graph_args, sample_trajectory_args, estimate_return_args):
        super(Agent, self).__init__()
        self.ob_dim = computation_graph_args['ob_dim']
        self.ac_dim = computation_graph_args['ac_dim']
        self.discrete = computation_graph_args['discrete']
        self.size = computation_graph_args['size']
        self.n_layers = computation_graph_args['n_layers']
        self.learning_rate = computation_graph_args['learning_rate']

        self.animate = sample_trajectory_args['animate']
        self.max_path_length = sample_trajectory_args['max_path_length']
        self.min_timesteps_per_batch = sample_trajectory_args['min_timesteps_per_batch']

        self.gamma = estimate_return_args['gamma']
        self.reward_to_go = estimate_return_args['reward_to_go']
        self.nn_baseline = estimate_return_args['nn_baseline']
        self.normalize_advantages = estimate_return_args['normalize_advantages']

    def init_tf_sess(self):
        tf_config = tf.ConfigProto(
            inter_op_parallelism_threads=1, intra_op_parallelism_threads=1)
        self.sess = tf.Session(config=tf_config)
        self.sess.__enter__()  # equivalent to `with self.sess:`
        tf.global_variables_initializer().run()  # pylint: disable=E1101

    def define_placeholders(self):
        """
            Placeholders for batch batch observations / actions / advantages in policy gradient 
            loss function.
            See Agent.build_computation_graph for notation

            returns:
                sy_ob_no: placeholder for observations
                sy_ac_na: placeholder for actions
                sy_adv_n: placeholder for advantages
        """
        sy_ob_no = tf.placeholder(
            shape=[None, self.ob_dim], name="ob", dtype=tf.float32)
        if self.discrete:
            sy_ac_na = tf.placeholder(shape=[None], name="ac", dtype=tf.int32)
        else:
            sy_ac_na = tf.placeholder(
                shape=[None, self.ac_dim], name="ac", dtype=tf.float32)
        sy_adv_n = tf.placeholder(name="ad", dtype=tf.float32)
        return sy_ob_no, sy_ac_na, sy_adv_n

    def policy_forward_pass(self, sy_ob_no):
        """ Constructs the symbolic operation for the policy network outputs,
            which are the parameters of the policy distribution p(a|s)

            arguments:
                sy_ob_no: (batch_size, self.ob_dim)

            returns:
                the parameters of the policy.

                if discrete, the parameters are the logits of a categorical distribution
                    over the actions
                    sy_logits_na: (batch_size, self.ac_dim)

                if continuous, the parameters are a tuple (mean, log_std) of a Gaussian
                    distribution over actions. log_std should just be a trainable
                    variable, not a network output.
                    sy_mean: (batch_size, self.ac_dim)
                    sy_logstd: (self.ac_dim,)

            Hint: use the 'build_mlp' function to output the logits (in the discrete case)
                and the mean (in the continuous case).
                Pass in self.n_layers for the 'n_layers' argument, and
                pass in self.size for the 'size' argument.
        """
        if self.discrete:
            sy_logits_na = build_mlp(input_placeholder=sy_ob_no, output_size=self.ac_dim, n_layers=self.n_layers,
                                     size=self.size, scope="logits")  # activation=tf.nn.relu, output_activation=None,
            return sy_logits_na
        else:
            sy_mean = build_mlp(input_placeholder=sy_ob_no, output_size=self.ac_dim, n_layers=self.n_layers, size=self.size,
                                output_activation=None, scope="mean")
            sy_logstd = tf.Variable(
                tf.zeros([1, self.ac_dim]), name='logstd', dtype=tf.float32)
            return (sy_mean, sy_logstd)

    def sample_action(self, policy_parameters):
        """ Constructs a symbolic operation for stochastically sampling from the policy
            distribution

            arguments:
                policy_parameters
                    if discrete: logits of a categorical distribution over actions 
                        sy_logits_na: (batch_size, self.ac_dim)
                    if continuous: (mean, log_std) of a Gaussian distribution over actions
                        sy_mean: (batch_size, self.ac_dim)
                        sy_logstd: (self.ac_dim,)

            returns:
                sy_sampled_ac: 
                    if discrete: (batch_size,)
                    if continuous: (batch_size, self.ac_dim)

            Hint: for the continuous case, use the reparameterization trick:
                 The output from a Gaussian distribution with mean 'mu' and std 'sigma' is

                      mu + sigma * z,         z ~ N(0, I)

                 This reduces the problem to just sampling z. (Hint: use tf.random_normal!)
        """
        if self.discrete:
            sy_logits_na = policy_parameters
            sy_sampled_ac = tf.squeeze(
                tf.multinomial(sy_logits_na, 1), axis=[1])

        else:
            sy_mean, sy_logstd = policy_parameters
            random_normal = tf.random_normal(shape=tf.shape(
                sy_mean), mean=0, stddev=1, dtype=tf.float32, name="random")
            sy_sampled_ac = sy_mean + tf.exp(sy_logstd) * random_normal

        return sy_sampled_ac

    def get_log_prob(self, policy_parameters, sy_ac_na):
        """ Constructs a symbolic operation for computing the log probability of a set of actions
            that were actually taken according to the policy

            arguments:
                policy_parameters
                    if discrete: logits of a categorical distribution over actions 
                        sy_logits_na: (batch_size, self.ac_dim)
                    if continuous: (mean, log_std) of a Gaussian distribution over actions
                        sy_mean: (batch_size, self.ac_dim)
                        sy_logstd: (self.ac_dim,)

                sy_ac_na: 
                    if discrete: (batch_size,)
                    if continuous: (batch_size, self.ac_dim)

            returns:
                sy_logprob_n: (batch_size)

            Hint:
                For the discrete case, use the log probability under a categorical distribution.
                For the continuous case, use the log probability under a multivariate gaussian.
        """
        if self.discrete:
            sy_logits_na = policy_parameters
            sy_logprob_n = - \
                tf.nn.sparse_softmax_cross_entropy_with_logits(
                    logits=sy_logits_na, labels=sy_ac_na)

        else:
            sy_mean, sy_logstd = policy_parameters
            mutltivariate = tf.contrib.distributions.MultivariateNormalDiag(
                loc=sy_mean, scale_diag=tf.exp(sy_logstd))
            sy_logprob_n = mutltivariate.log_prob(
                value=sy_ac_na, name="log_prob")
        return sy_logprob_n

    def build_computation_graph(self):
        """
            Notes on notation:

            Symbolic variables have the prefix sy_, to distinguish them from the numerical values
            that are computed later in the function

            Prefixes and suffixes:
            ob - observation 
            ac - action
            _no - this tensor should have shape (batch self.size /n/, observation dim)
            _na - this tensor should have shape (batch self.size /n/, action dim)
            _n  - this tensor should have shape (batch self.size /n/)

            Note: batch self.size /n/ is defined at runtime, and until then, the shape for that axis
            is None

            ----------------------------------------------------------------------------------
            loss: a function of self.sy_logprob_n and self.sy_adv_n that we will differentiate
                to get the policy gradient.
        """
        self.sy_ob_no, self.sy_ac_na, self.sy_adv_n = self.define_placeholders()

        # The policy takes in an observation and produces a distribution over the action space
        self.policy_parameters = self.policy_forward_pass(self.sy_ob_no)

        # We can sample actions from this action distribution.
        # This will be called in Agent.sample_trajectory() where we generate a rollout.
        self.sy_sampled_ac = self.sample_action(self.policy_parameters)

        # We can also compute the logprob of the actions that were actually taken by the policy
        # This is used in the loss function.
        self.sy_logprob_n = self.get_log_prob(
            self.policy_parameters, self.sy_ac_na)

        #========================================================================================#
        # Loss Function and Training Operation
        #========================================================================================#
        loss = - tf.reduce_mean(self.sy_logprob_n *
                                self.sy_adv_n, name="loss")  # YOUR CODE HERE
        self.update_op = tf.train.AdamOptimizer(
            self.learning_rate).minimize(loss)

        #========================================================================================#
        # Optional Baseline
        #
        # Define placeholders for targets, a loss function and an update op for fitting a
        # neural network baseline. These will be used to fit the neural network baseline.
        #========================================================================================#
        if self.nn_baseline:
            self.baseline_prediction = tf.squeeze(build_mlp(
                self.sy_ob_no,
                1,
                "nn_baseline",
                n_layers=self.n_layers,
                size=self.size))
            # YOUR_CODE_HERE
            self.sy_target_n = tf.placeholder(shape=[None], dtype=tf.float32)
            baseline_loss = tf.nn.l2_loss(
                self.baseline_prediction - self.sy_target_n)
            self.baseline_update_op = tf.train.AdamOptimizer(
                self.learning_rate).minimize(baseline_loss)

    def sample_trajectories(self, itr, env):
        # Collect paths until we have enough timesteps
        timesteps_this_batch = 0
        paths = []
        while True:
            animate_this_episode = (len(paths) == 0 and (
                itr % 10 == 0) and self.animate)
            path = self.sample_trajectory(env, animate_this_episode)
            paths.append(path)
            timesteps_this_batch += pathlength(path)
            if timesteps_this_batch >= self.min_timesteps_per_batch:
                break
        return paths, timesteps_this_batch

    def sample_trajectory(self, env, animate_this_episode):
        ob = env.reset()
        obs, acs, rewards = [], [], []
        steps = 0
        while True:
            if animate_this_episode:
                env.render()
                time.sleep(0.1)
            obs.append(ob)
            ac = tf.get_default_session().run(self.sy_sampled_ac, feed_dict={
                self.sy_ob_no: ob[None]})  # YOUR CODE HERE
            ac = ac[0]
            acs.append(ac)
            ob, rew, done, _ = env.step(ac)
            rewards.append(rew)
            steps += 1
            if done or steps > self.max_path_length:
                break
        path = {"observation": np.array(obs, dtype=np.float32),
                "reward": np.array(rewards, dtype=np.float32),
                "action": np.array(acs, dtype=np.float32)}
        return path

    def sum_of_rewards(self, re_n):
        """
            Monte Carlo estimation of the Q function.

            let sum_of_path_lengths be the sum of the lengths of the paths sampled from 
                Agent.sample_trajectories
            let num_paths be the number of paths sampled from Agent.sample_trajectories

            arguments:
                re_n: length: num_paths. Each element in re_n is a numpy array 
                    containing the rewards for the particular path

            returns:
                q_n: shape: (sum_of_path_lengths). A single vector for the estimated q values 
                    whose length is the sum of the lengths of the paths

            ----------------------------------------------------------------------------------

            Your code should construct numpy arrays for Q-values which will be used to compute
            advantages (which will in turn be fed to the placeholder you defined in 
            Agent.define_placeholders). 

            Recall that the expression for the policy gradient PG is

                  PG = E_{tau} [sum_{t=0}^T grad log pi(a_t|s_t) * (Q_t - b_t )]

            where 

                  tau=(s_0, a_0, ...) is a trajectory,
                  Q_t is the Q-value at time t, Q^{pi}(s_t, a_t),
                  and b_t is a baseline which may depend on s_t. 

            You will write code for two cases, controlled by the flag 'reward_to_go':

              Case 1: trajectory-based PG 

                  (reward_to_go = False)

                  Instead of Q^{pi}(s_t, a_t), we use the total discounted reward summed over 
                  entire trajectory (regardless of which time step the Q-value should be for). 

                  For this case, the policy gradient estimator is

                      E_{tau} [sum_{t=0}^T grad log pi(a_t|s_t) * Ret(tau)]

                  where

                      Ret(tau) = sum_{t'=0}^T gamma^t' r_{t'}.

                  Thus, you should compute

                      Q_t = Ret(tau)

              Case 2: reward-to-go PG 

                  (reward_to_go = True)

                  Here, you estimate Q^{pi}(s_t, a_t) by the discounted sum of rewards starting
                  from time step t. Thus, you should compute

                      Q_t = sum_{t'=t}^T gamma^(t'-t) * r_{t'}


            Store the Q-values for all timesteps and all trajectories in a variable 'q_n',
            like the 'ob_no' and 'ac_na' above. 
        """
        q_n = []
        if self.reward_to_go:
            for path_rewards in re_n:
                discounts = np.power(self.gamma, np.arange(len(path_rewards)))
                for (t, reward) in enumerate(path_rewards):
                    q_n.append(np.sum(path_rewards[t:] * discounts[t:]))

        else:
            for path_rewards in re_n:
                discounts = np.power(self.gamma, np.arange(len(path_rewards)))
                re = np.sum(path_rewards * discounts)
                for i in range(len(path_rewards)):
                    q_n.append(re)
        return q_n

    def compute_advantage(self, ob_no, q_n):
        """
            Computes advantages by (possibly) subtracting a baseline from the estimated Q values

            let sum_of_path_lengths be the sum of the lengths of the paths sampled from 
                Agent.sample_trajectories
            let num_paths be the number of paths sampled from Agent.sample_trajectories

            arguments:
                ob_no: shape: (sum_of_path_lengths, ob_dim)
                q_n: shape: (sum_of_path_lengths). A single vector for the estimated q values 
                    whose length is the sum of the lengths of the paths

            returns:
                adv_n: shape: (sum_of_path_lengths). A single vector for the estimated 
                    advantages whose length is the sum of the lengths of the paths
        """
        #====================================================================================#
        # Computing Baselines
        #====================================================================================#
        if self.nn_baseline:
            # If nn_baseline is True, use your neural network to predict reward-to-go
            # at each timestep for each trajectory, and save the result in a variable 'b_n'
            # like 'ob_no', 'ac_na', and 'q_n'.
            #
            # Hint #bl1: rescale the output from the nn_baseline to match the statistics
            # (mean and std) of the current batch of Q-values. (Goes with Hint
            # #bl2 in Agent.update_parameters.
            eps = 1e-8
            b_n = tf.get_default_session().run(self.baseline_prediction,
                                               feed_dict={self.sy_ob_no: ob_no})
            b_n = (b_n - np.mean(b_n)) / (np.std(b_n) + eps)  # YOUR CODE HERE
            adv_n = q_n - b_n
        else:
            adv_n = q_n.copy()
        return adv_n

    def estimate_return(self, ob_no, re_n):
        """
            Estimates the returns over a set of trajectories.

            let sum_of_path_lengths be the sum of the lengths of the paths sampled from 
                Agent.sample_trajectories
            let num_paths be the number of paths sampled from Agent.sample_trajectories

            arguments:
                ob_no: shape: (sum_of_path_lengths, ob_dim)
                re_n: length: num_paths. Each element in re_n is a numpy array 
                    containing the rewards for the particular path

            returns:
                q_n: shape: (sum_of_path_lengths). A single vector for the estimated q values 
                    whose length is the sum of the lengths of the paths
                adv_n: shape: (sum_of_path_lengths). A single vector for the estimated 
                    advantages whose length is the sum of the lengths of the paths
        """
        q_n = self.sum_of_rewards(re_n)
        adv_n = self.compute_advantage(ob_no, q_n)
        #====================================================================================#
        # Advantage Normalization
        #====================================================================================#
        if self.normalize_advantages:
            # On the next line, implement a trick which is known empirically to reduce variance
            # in policy gradient methods: normalize adv_n to have mean zero and std=1.
            eps = 1e-8
            adv_n = (adv_n - np.mean(adv_n)) / \
                (np.std(adv_n) + eps)
        return q_n, adv_n

    def update_parameters(self, ob_no, ac_na, q_n, adv_n):
        """ 
            Update the parameters of the policy and (possibly) the neural network baseline, 
            which is trained to approximate the value function.

            arguments:
                ob_no: shape: (sum_of_path_lengths, ob_dim)
                ac_na: shape: (sum_of_path_lengths).
                q_n: shape: (sum_of_path_lengths). A single vector for the estimated q values 
                    whose length is the sum of the lengths of the paths
                adv_n: shape: (sum_of_path_lengths). A single vector for the estimated 
                    advantages whose length is the sum of the lengths of the paths

            returns:
                nothing

        """
        #====================================================================================#
        # Optimizing Neural Network Baseline
        #====================================================================================#
        if self.nn_baseline:
            # If a neural network baseline is used, set up the targets and the inputs for the
            # baseline.
            #
            # Fit it to the current batch in order to use for the next iteration. Use the
            # baseline_update_op you defined earlier.
            #
            # Hint #bl2: Instead of trying to target raw Q-values directly, rescale the
            # targets to have mean zero and std=1. (Goes with Hint #bl1 in
            # Agent.compute_advantage.)

            # YOUR_CODE_HERE
            eps = 1e-8
            target_n = (q_n - np.mean(q_n)) / (np.std(q_n) + eps)
            _ = tf.get_default_session().run(self.baseline_update_op, feed_dict={
                self.sy_ob_no: ob_no, self.sy_target_n: target_n})

        #====================================================================================#
        # Performing the Policy Update
        #====================================================================================#

        # Call the update operation necessary to perform the policy gradient update based on
        # the current batch of rollouts.
        #
        # For debug purposes, you may wish to save the value of the loss function before
        # and after an update, and then log them below.

        sess = tf.get_default_session()
        feed_dict = {self.sy_ob_no: ob_no,
                     self.sy_ac_na: ac_na, self.sy_adv_n: q_n}
        sess.run(self.update_op, feed_dict=feed_dict)


def train_PG(
        exp_name,
        # env_name,
        n_iter,
        gamma,
        min_timesteps_per_batch,
        max_path_length,
        learning_rate,
        reward_to_go,
        animate,
        logdir,
        normalize_advantages,
        nn_baseline,
        seed,
        n_layers,
        size):

    start = time.time()

    #========================================================================================#
    # Set Up Logger
    #========================================================================================#
    setup_logger(logdir, locals())

    #========================================================================================#
    # Set Up Env
    #========================================================================================#

    # Make the gym environment
    # env = gym.make(env_name)
    env = SupplyDistribution(n_stores=1,
                             cap_truck=3,
                             prod_cost=1,
                             max_prod=2,
                             store_cost=np.array([0, 0]),
                             truck_cost=np.array([0]),
                             cap_store=np.array([30, 10]),
                             penalty_cost=1,
                             price=1,
                             gamma=1,
                             max_demand=4,
                             episode_length=max_path_length)

    # special_environment
    # env = SupplyDistribution(n_stores=3,
    #                          cap_truck=2,
    #                          prod_cost=1,
    #                          max_prod=3,
    #                          store_cost=np.array([0, 2, 0, 0]),
    #                          truck_cost=np.array([3, 3, 0]),
    #                          cap_store=np.array([50, 10, 10, 10]),
    #                          penalty_cost=1,
    #                          price=2.5,
    #                          gamma=1,
    #                          max_demand=3,
    #                          episode_length=max_path_length)

    # Set random seeds
    tf.set_random_seed(seed)
    np.random.seed(seed)
    # env.seed(seed)

    # Maximum length for episodes
    max_path_length = max_path_length or env.spec.max_episode_steps

    # Is this env continuous, or self.discrete?
    discrete = isinstance(env.action_space, gym.spaces.Discrete)

    # Observation and action sizes
    ob_dim = env.observation_space.shape[0]
    ac_dim = env.action_space.n if discrete else env.action_space.shape[0]

    #========================================================================================#
    # Initialize Agent
    #========================================================================================#
    computation_graph_args = {
        'n_layers': n_layers,
        'ob_dim': ob_dim,
        'ac_dim': ac_dim,
        'discrete': discrete,
        'size': size,
        'learning_rate': learning_rate,
    }

    sample_trajectory_args = {
        'animate': animate,
        'max_path_length': max_path_length,
        'min_timesteps_per_batch': min_timesteps_per_batch,
    }

    estimate_return_args = {
        'gamma': gamma,
        'reward_to_go': reward_to_go,
        'nn_baseline': nn_baseline,
        'normalize_advantages': normalize_advantages,
    }

    agent = Agent(computation_graph_args,
                  sample_trajectory_args, estimate_return_args)

    # build computation graph
    agent.build_computation_graph()

    # tensorflow: config, session, variable initialization
    agent.init_tf_sess()

    #========================================================================================#
    # Training Loop
    #========================================================================================#

    total_timesteps = 0
    for itr in range(n_iter):
        print("********** Iteration %i ************" % itr)
        paths, timesteps_this_batch = agent.sample_trajectories(itr, env)
        total_timesteps += timesteps_this_batch

        # Build arrays for observation, action for the policy gradient update by concatenating
        # across paths
        ob_no = np.concatenate([path["observation"] for path in paths])
        ac_na = np.concatenate([path["action"] for path in paths])
        re_n = [path["reward"] for path in paths]

        q_n, adv_n = agent.estimate_return(ob_no, re_n)
        agent.update_parameters(ob_no, ac_na, q_n, adv_n)

        # Log diagnostics
        # print(paths)
        returns = [path["reward"].sum() for path in paths]
        ep_lengths = [pathlength(path) for path in paths]
        logz.log_tabular("Time", time.time() - start)
        logz.log_tabular("Iteration", itr)
        logz.log_tabular("AverageReturn", np.mean(returns))
        logz.log_tabular("StdReturn", np.std(returns))
        logz.log_tabular("MaxReturn", np.max(returns))
        logz.log_tabular("MinReturn", np.min(returns))
        logz.log_tabular("EpLenMean", np.mean(ep_lengths))
        logz.log_tabular("EpLenStd", np.std(ep_lengths))
        logz.log_tabular("TimestepsThisBatch", timesteps_this_batch)
        logz.log_tabular("TimestepsSoFar", total_timesteps)
        logz.dump_tabular()
        logz.pickle_tf_vars()


def main():
    import argparse
    parser = argparse.ArgumentParser()
    # parser.add_argument('env_name', type=str)
    parser.add_argument('--exp_name', type=str, default='vpg')
    parser.add_argument('--render', action='store_true')
    parser.add_argument('--discount', type=float, default=1.0)
    parser.add_argument('--n_iter', '-n', type=int, default=100)
    parser.add_argument('--batch_size', '-b', type=int, default=1000)
    parser.add_argument('--ep_len', '-ep', type=float, default=-1.)
    parser.add_argument('--learning_rate', '-lr', type=float, default=5e-3)
    parser.add_argument('--reward_to_go', '-rtg', action='store_true')
    parser.add_argument('--dont_normalize_advantages',
                        '-dna', action='store_true')
    parser.add_argument('--nn_baseline', '-bl', action='store_true')
    parser.add_argument('--seed', type=int, default=1)
    parser.add_argument('--n_experiments', '-e', type=int, default=1)
    parser.add_argument('--n_layers', '-l', type=int, default=2)
    parser.add_argument('--size', '-s', type=int, default=64)
    args = parser.parse_args()

    if not(os.path.exists('data')):
        os.makedirs('data')
    logdir = args.exp_name + '_' + time.strftime("%d-%m-%Y_%H-%M-%S")
    logdir = os.path.join('data', logdir)
    if not(os.path.exists(logdir)):
        os.makedirs(logdir)

    max_path_length = args.ep_len if args.ep_len > 0 else None

    processes = []

    for e in range(args.n_experiments):
        seed = args.seed + 10 * e
        print('Running experiment with seed %d' % seed)

        def train_func():
            train_PG(
                exp_name=args.exp_name,
                # env_name=args.env_name,
                n_iter=args.n_iter,
                gamma=args.discount,
                min_timesteps_per_batch=args.batch_size,
                max_path_length=max_path_length,
                learning_rate=args.learning_rate,
                reward_to_go=args.reward_to_go,
                animate=args.render,
                logdir=os.path.join(logdir, '%d' % seed),
                normalize_advantages=not(args.dont_normalize_advantages),
                nn_baseline=args.nn_baseline,
                seed=seed,
                n_layers=args.n_layers,
                size=args.size
            )
        # # Awkward hacky process runs, because Tensorflow does not like
        # # repeatedly calling train_PG in the same thread.
        p = Process(target=train_func, args=tuple())
        p.start()
        processes.append(p)
        # if you comment in the line below, then the loop will block
        # until this process finishes
        # p.join()

    for p in processes:
        p.join()


if __name__ == "__main__":
    main()