diff --git a/python/ray/rllib/agents/ddpg/ddpg_policy.py b/python/ray/rllib/agents/ddpg/ddpg_policy.py
index ad9f4baf8..2ddc18950 100644
--- a/python/ray/rllib/agents/ddpg/ddpg_policy.py
+++ b/python/ray/rllib/agents/ddpg/ddpg_policy.py
@@ -75,6 +75,12 @@ class DDPGTFPolicy(DDPGPostprocessing, TFPolicy):
             raise UnsupportedSpaceException(
                 "Action space {} is not supported for DDPG.".format(
                     action_space))
+        if len(action_space.shape) > 1:
+            raise UnsupportedSpaceException(
+                "Action space has multiple dimensions "
+                "{}. ".format(action_space.shape) +
+                "Consider reshaping this into a single dimension, "
+                "using a Tuple action space, or the multi-agent API.")
 
         self.config = config
         self.cur_noise_scale = 1.0
diff --git a/python/ray/rllib/agents/dqn/distributional_q_model.py b/python/ray/rllib/agents/dqn/distributional_q_model.py
index de0c0dbe6..adede90f9 100644
--- a/python/ray/rllib/agents/dqn/distributional_q_model.py
+++ b/python/ray/rllib/agents/dqn/distributional_q_model.py
@@ -166,6 +166,12 @@ class DistributionalQModel(TFModelV2):
             self.state_value_head = tf.keras.Model(self.model_out, state_out)
             self.register_variables(self.state_value_head.variables)
 
+    def forward(self, input_dict, state, seq_lens):
+        """This generates the model_out tensor input.
+
+        You must implement this as documented in modelv2.py."""
+        raise NotImplementedError
+
     def get_q_value_distributions(self, model_out):
         """Returns distributional values for Q(s, a) given a state embedding.
 
diff --git a/python/ray/rllib/agents/dqn/dqn_policy.py b/python/ray/rllib/agents/dqn/dqn_policy.py
index c2e22f721..0865b24d5 100644
--- a/python/ray/rllib/agents/dqn/dqn_policy.py
+++ b/python/ray/rllib/agents/dqn/dqn_policy.py
@@ -191,7 +191,8 @@ def build_q_model(policy, obs_space, action_space, config):
             "Action space {} is not supported for DQN.".format(action_space))
 
     if config["hiddens"]:
-        num_outputs = 256
+        # try to infer the last layer size, otherwise fall back to 256
+        num_outputs = ([256] + config["model"]["fcnet_hiddens"])[-1]
         config["model"]["no_final_linear"] = True
     else:
         num_outputs = action_space.n
diff --git a/python/ray/rllib/agents/dqn/simple_q_model.py b/python/ray/rllib/agents/dqn/simple_q_model.py
index d9815205f..a365af658 100644
--- a/python/ray/rllib/agents/dqn/simple_q_model.py
+++ b/python/ray/rllib/agents/dqn/simple_q_model.py
@@ -54,6 +54,12 @@ class SimpleQModel(TFModelV2):
         self.q_value_head = tf.keras.Model(self.model_out, q_out)
         self.register_variables(self.q_value_head.variables)
 
+    def forward(self, input_dict, state, seq_lens):
+        """This generates the model_out tensor input.
+
+        You must implement this as documented in modelv2.py."""
+        raise NotImplementedError
+
     def get_q_values(self, model_out):
         """Returns Q(s, a) given a feature tensor for the state.
 
diff --git a/python/ray/rllib/agents/impala/vtrace_policy.py b/python/ray/rllib/agents/impala/vtrace_policy.py
index 9b283c717..e3fa88348 100644
--- a/python/ray/rllib/agents/impala/vtrace_policy.py
+++ b/python/ray/rllib/agents/impala/vtrace_policy.py
@@ -6,24 +6,23 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
-import gym
-import ray
 import numpy as np
+import logging
+import gym
+
+import ray
 from ray.rllib.agents.impala import vtrace
-from ray.rllib.evaluation.metrics import LEARNER_STATS_KEY
-from ray.rllib.policy.policy import Policy
-from ray.rllib.policy.sample_batch import SampleBatch
-from ray.rllib.policy.tf_policy import TFPolicy, \
-    LearningRateSchedule
 from ray.rllib.models.action_dist import Categorical
-from ray.rllib.models.catalog import ModelCatalog
-from ray.rllib.utils.annotations import override
+from ray.rllib.policy.sample_batch import SampleBatch
+from ray.rllib.policy.tf_policy_template import build_tf_policy
+from ray.rllib.policy.tf_policy import LearningRateSchedule
 from ray.rllib.utils.explained_variance import explained_variance
 from ray.rllib.utils import try_import_tf
 
 tf = try_import_tf()
 
-# Frozen logits of the policy that computed the action
+logger = logging.getLogger(__name__)
+
 BEHAVIOUR_LOGITS = "behaviour_logits"
 
 
@@ -88,6 +87,7 @@ class VTraceLoss(object):
                 clip_rho_threshold=tf.cast(clip_rho_threshold, tf.float32),
                 clip_pg_rho_threshold=tf.cast(clip_pg_rho_threshold,
                                               tf.float32))
+            self.value_targets = self.vtrace_returns.vs
 
         # The policy gradients loss
         self.pi_loss = -tf.reduce_sum(
@@ -107,237 +107,191 @@ class VTraceLoss(object):
                            self.entropy * entropy_coeff)
 
 
-class VTracePostprocessing(object):
-    """Adds the policy logits to the trajectory."""
+def _make_time_major(policy, tensor, drop_last=False):
+    """Swaps batch and trajectory axis.
 
-    @override(TFPolicy)
-    def extra_compute_action_fetches(self):
-        return dict(
-            TFPolicy.extra_compute_action_fetches(self),
-            **{BEHAVIOUR_LOGITS: self.model.outputs})
+    Arguments:
+        policy: Policy reference
+        tensor: A tensor or list of tensors to reshape.
+        drop_last: A bool indicating whether to drop the last
+        trajectory item.
 
-    @override(Policy)
-    def postprocess_trajectory(self,
-                               sample_batch,
-                               other_agent_batches=None,
-                               episode=None):
-        # not used, so save some bandwidth
-        del sample_batch.data[SampleBatch.NEXT_OBS]
-        return sample_batch
+    Returns:
+        res: A tensor with swapped axes or a list of tensors with
+        swapped axes.
+    """
+    if isinstance(tensor, list):
+        return [_make_time_major(policy, t, drop_last) for t in tensor]
+
+    if policy.state_in:
+        B = tf.shape(policy.seq_lens)[0]
+        T = tf.shape(tensor)[0] // B
+    else:
+        # Important: chop the tensor into batches at known episode cut
+        # boundaries. TODO(ekl) this is kind of a hack
+        T = policy.config["sample_batch_size"]
+        B = tf.shape(tensor)[0] // T
+    rs = tf.reshape(tensor, tf.concat([[B, T], tf.shape(tensor)[1:]], axis=0))
+
+    # swap B and T axes
+    res = tf.transpose(
+        rs, [1, 0] + list(range(2, 1 + int(tf.shape(tensor).shape[0]))))
+
+    if drop_last:
+        return res[:-1]
+    return res
 
 
-class VTraceTFPolicy(LearningRateSchedule, VTracePostprocessing, TFPolicy):
-    def __init__(self,
-                 observation_space,
-                 action_space,
-                 config,
-                 existing_inputs=None):
-        config = dict(ray.rllib.agents.impala.impala.DEFAULT_CONFIG, **config)
-        assert config["batch_mode"] == "truncate_episodes", \
-            "Must use `truncate_episodes` batch mode with V-trace."
-        self.config = config
-        self.sess = tf.get_default_session()
-        self.grads = None
+def build_vtrace_loss(policy, batch_tensors):
+    if isinstance(policy.action_space, gym.spaces.Discrete):
+        is_multidiscrete = False
+        output_hidden_shape = [policy.action_space.n]
+    elif isinstance(policy.action_space,
+                    gym.spaces.multi_discrete.MultiDiscrete):
+        is_multidiscrete = True
+        output_hidden_shape = policy.action_space.nvec.astype(np.int32)
+    else:
+        is_multidiscrete = False
+        output_hidden_shape = 1
 
-        if isinstance(action_space, gym.spaces.Discrete):
-            is_multidiscrete = False
-            output_hidden_shape = [action_space.n]
-        elif isinstance(action_space, gym.spaces.multi_discrete.MultiDiscrete):
-            is_multidiscrete = True
-            output_hidden_shape = action_space.nvec.astype(np.int32)
-        else:
-            is_multidiscrete = False
-            output_hidden_shape = 1
+    def make_time_major(*args, **kw):
+        return _make_time_major(policy, *args, **kw)
 
-        # Create input placeholders
-        dist_class, logit_dim = ModelCatalog.get_action_dist(
-            action_space, self.config["model"])
-        if existing_inputs:
-            actions, dones, behaviour_logits, rewards, observations, \
-                prev_actions, prev_rewards = existing_inputs[:7]
-            existing_state_in = existing_inputs[7:-1]
-            existing_seq_lens = existing_inputs[-1]
-        else:
-            actions = ModelCatalog.get_action_placeholder(action_space)
-            dones = tf.placeholder(tf.bool, [None], name="dones")
-            rewards = tf.placeholder(tf.float32, [None], name="rewards")
-            behaviour_logits = tf.placeholder(
-                tf.float32, [None, logit_dim], name="behaviour_logits")
-            observations = tf.placeholder(
-                tf.float32, [None] + list(observation_space.shape))
-            existing_state_in = None
-            existing_seq_lens = None
+    actions = batch_tensors[SampleBatch.ACTIONS]
+    dones = batch_tensors[SampleBatch.DONES]
+    rewards = batch_tensors[SampleBatch.REWARDS]
+    behaviour_logits = batch_tensors[BEHAVIOUR_LOGITS]
+    unpacked_behaviour_logits = tf.split(
+        behaviour_logits, output_hidden_shape, axis=1)
+    unpacked_outputs = tf.split(policy.model_out, output_hidden_shape, axis=1)
+    action_dist = policy.action_dist
+    values = policy.value_function
 
-        # Unpack behaviour logits
-        unpacked_behaviour_logits = tf.split(
-            behaviour_logits, output_hidden_shape, axis=1)
+    if policy.state_in:
+        max_seq_len = tf.reduce_max(policy.seq_lens) - 1
+        mask = tf.sequence_mask(policy.seq_lens, max_seq_len)
+        mask = tf.reshape(mask, [-1])
+    else:
+        mask = tf.ones_like(rewards)
 
-        # Setup the policy
-        prev_actions = ModelCatalog.get_action_placeholder(action_space)
-        prev_rewards = tf.placeholder(tf.float32, [None], name="prev_reward")
-        self.model = ModelCatalog.get_model(
-            {
-                "obs": observations,
-                "prev_actions": prev_actions,
-                "prev_rewards": prev_rewards,
-                "is_training": self._get_is_training_placeholder(),
-            },
-            observation_space,
-            action_space,
-            logit_dim,
-            self.config["model"],
-            state_in=existing_state_in,
-            seq_lens=existing_seq_lens)
-        unpacked_outputs = tf.split(
-            self.model.outputs, output_hidden_shape, axis=1)
+    # Prepare actions for loss
+    loss_actions = actions if is_multidiscrete else tf.expand_dims(
+        actions, axis=1)
 
-        action_dist = dist_class(self.model.outputs)
+    # Inputs are reshaped from [B * T] => [T - 1, B] for V-trace calc.
+    policy.loss = VTraceLoss(
+        actions=make_time_major(loss_actions, drop_last=True),
+        actions_logp=make_time_major(
+            action_dist.logp(actions), drop_last=True),
+        actions_entropy=make_time_major(action_dist.entropy(), drop_last=True),
+        dones=make_time_major(dones, drop_last=True),
+        behaviour_logits=make_time_major(
+            unpacked_behaviour_logits, drop_last=True),
+        target_logits=make_time_major(unpacked_outputs, drop_last=True),
+        discount=policy.config["gamma"],
+        rewards=make_time_major(rewards, drop_last=True),
+        values=make_time_major(values, drop_last=True),
+        bootstrap_value=make_time_major(values)[-1],
+        dist_class=Categorical if is_multidiscrete else policy.dist_class,
+        valid_mask=make_time_major(mask, drop_last=True),
+        vf_loss_coeff=policy.config["vf_loss_coeff"],
+        entropy_coeff=policy.config["entropy_coeff"],
+        clip_rho_threshold=policy.config["vtrace_clip_rho_threshold"],
+        clip_pg_rho_threshold=policy.config["vtrace_clip_pg_rho_threshold"])
 
-        values = self.model.value_function()
+    return policy.loss.total_loss
+
+
+def stats(policy, batch_tensors):
+    values_batched = _make_time_major(
+        policy, policy.value_function, drop_last=policy.config["vtrace"])
+
+    return {
+        "cur_lr": tf.cast(policy.cur_lr, tf.float64),
+        "policy_loss": policy.loss.pi_loss,
+        "entropy": policy.loss.entropy,
+        "var_gnorm": tf.global_norm(policy.var_list),
+        "vf_loss": policy.loss.vf_loss,
+        "vf_explained_var": explained_variance(
+            tf.reshape(policy.loss.value_targets, [-1]),
+            tf.reshape(values_batched, [-1])),
+    }
+
+
+def grad_stats(policy, grads):
+    return {
+        "grad_gnorm": tf.global_norm(grads),
+    }
+
+
+def postprocess_trajectory(policy,
+                           sample_batch,
+                           other_agent_batches=None,
+                           episode=None):
+    # not used, so save some bandwidth
+    del sample_batch.data[SampleBatch.NEXT_OBS]
+    return sample_batch
+
+
+def add_behaviour_logits(policy):
+    return {BEHAVIOUR_LOGITS: policy.model_out}
+
+
+def validate_config(policy, obs_space, action_space, config):
+    assert config["batch_mode"] == "truncate_episodes", \
+        "Must use `truncate_episodes` batch mode with V-trace."
+
+
+def choose_optimizer(policy, config):
+    if policy.config["opt_type"] == "adam":
+        return tf.train.AdamOptimizer(policy.cur_lr)
+    else:
+        return tf.train.RMSPropOptimizer(policy.cur_lr, config["decay"],
+                                         config["momentum"], config["epsilon"])
+
+
+def clip_gradients(policy, optimizer, loss):
+    grads = tf.gradients(loss, policy.var_list)
+    policy.grads, _ = tf.clip_by_global_norm(grads, policy.config["grad_clip"])
+    clipped_grads = list(zip(policy.grads, policy.var_list))
+    return clipped_grads
+
+
+class ValueNetworkMixin(object):
+    def __init__(self):
+        self.value_function = self.model.value_function()
         self.var_list = tf.get_collection(tf.GraphKeys.TRAINABLE_VARIABLES,
                                           tf.get_variable_scope().name)
 
-        def make_time_major(tensor, drop_last=False):
-            """Swaps batch and trajectory axis.
-            Args:
-                tensor: A tensor or list of tensors to reshape.
-                drop_last: A bool indicating whether to drop the last
-                trajectory item.
-            Returns:
-                res: A tensor with swapped axes or a list of tensors with
-                swapped axes.
-            """
-            if isinstance(tensor, list):
-                return [make_time_major(t, drop_last) for t in tensor]
-
-            if self.model.state_init:
-                B = tf.shape(self.model.seq_lens)[0]
-                T = tf.shape(tensor)[0] // B
-            else:
-                # Important: chop the tensor into batches at known episode cut
-                # boundaries. TODO(ekl) this is kind of a hack
-                T = self.config["sample_batch_size"]
-                B = tf.shape(tensor)[0] // T
-            rs = tf.reshape(tensor,
-                            tf.concat([[B, T], tf.shape(tensor)[1:]], axis=0))
-
-            # swap B and T axes
-            res = tf.transpose(
-                rs,
-                [1, 0] + list(range(2, 1 + int(tf.shape(tensor).shape[0]))))
-
-            if drop_last:
-                return res[:-1]
-            return res
-
-        if self.model.state_in:
-            max_seq_len = tf.reduce_max(self.model.seq_lens) - 1
-            mask = tf.sequence_mask(self.model.seq_lens, max_seq_len)
-            mask = tf.reshape(mask, [-1])
-        else:
-            mask = tf.ones_like(rewards, dtype=tf.bool)
-
-        # Prepare actions for loss
-        loss_actions = actions if is_multidiscrete else tf.expand_dims(
-            actions, axis=1)
-
-        # Inputs are reshaped from [B * T] => [T - 1, B] for V-trace calc.
-        self.loss = VTraceLoss(
-            actions=make_time_major(loss_actions, drop_last=True),
-            actions_logp=make_time_major(
-                action_dist.logp(actions), drop_last=True),
-            actions_entropy=make_time_major(
-                action_dist.entropy(), drop_last=True),
-            dones=make_time_major(dones, drop_last=True),
-            behaviour_logits=make_time_major(
-                unpacked_behaviour_logits, drop_last=True),
-            target_logits=make_time_major(unpacked_outputs, drop_last=True),
-            discount=config["gamma"],
-            rewards=make_time_major(rewards, drop_last=True),
-            values=make_time_major(values, drop_last=True),
-            bootstrap_value=make_time_major(values)[-1],
-            dist_class=Categorical if is_multidiscrete else dist_class,
-            valid_mask=make_time_major(mask, drop_last=True),
-            vf_loss_coeff=self.config["vf_loss_coeff"],
-            entropy_coeff=self.config["entropy_coeff"],
-            clip_rho_threshold=self.config["vtrace_clip_rho_threshold"],
-            clip_pg_rho_threshold=self.config["vtrace_clip_pg_rho_threshold"])
-
-        # Initialize TFPolicy
-        loss_in = [
-            (SampleBatch.ACTIONS, actions),
-            (SampleBatch.DONES, dones),
-            (BEHAVIOUR_LOGITS, behaviour_logits),
-            (SampleBatch.REWARDS, rewards),
-            (SampleBatch.CUR_OBS, observations),
-            (SampleBatch.PREV_ACTIONS, prev_actions),
-            (SampleBatch.PREV_REWARDS, prev_rewards),
-        ]
-        LearningRateSchedule.__init__(self, self.config["lr"],
-                                      self.config["lr_schedule"])
-        TFPolicy.__init__(
-            self,
-            observation_space,
-            action_space,
-            self.sess,
-            obs_input=observations,
-            action_sampler=action_dist.sample(),
-            action_prob=action_dist.sampled_action_prob(),
-            loss=self.loss.total_loss,
-            model=self.model,
-            loss_inputs=loss_in,
-            state_inputs=self.model.state_in,
-            state_outputs=self.model.state_out,
-            prev_action_input=prev_actions,
-            prev_reward_input=prev_rewards,
-            seq_lens=self.model.seq_lens,
-            max_seq_len=self.config["model"]["max_seq_len"],
-            batch_divisibility_req=self.config["sample_batch_size"])
-
-        self.sess.run(tf.global_variables_initializer())
-
-        self.stats_fetches = {
-            LEARNER_STATS_KEY: {
-                "cur_lr": tf.cast(self.cur_lr, tf.float64),
-                "policy_loss": self.loss.pi_loss,
-                "entropy": self.loss.entropy,
-                "grad_gnorm": tf.global_norm(self._grads),
-                "var_gnorm": tf.global_norm(self.var_list),
-                "vf_loss": self.loss.vf_loss,
-                "vf_explained_var": explained_variance(
-                    tf.reshape(self.loss.vtrace_returns.vs, [-1]),
-                    tf.reshape(make_time_major(values, drop_last=True), [-1])),
-            },
+    def value(self, ob, *args):
+        feed_dict = {
+            self.get_placeholder(SampleBatch.CUR_OBS): [ob],
+            self.seq_lens: [1]
         }
+        assert len(args) == len(self.state_in), \
+            (args, self.state_in)
+        for k, v in zip(self.state_in, args):
+            feed_dict[k] = v
+        vf = self.get_session().run(self.value_function, feed_dict)
+        return vf[0]
 
-    @override(TFPolicy)
-    def copy(self, existing_inputs):
-        return VTraceTFPolicy(
-            self.observation_space,
-            self.action_space,
-            self.config,
-            existing_inputs=existing_inputs)
 
-    @override(TFPolicy)
-    def optimizer(self):
-        if self.config["opt_type"] == "adam":
-            return tf.train.AdamOptimizer(self.cur_lr)
-        else:
-            return tf.train.RMSPropOptimizer(self.cur_lr, self.config["decay"],
-                                             self.config["momentum"],
-                                             self.config["epsilon"])
+def setup_mixins(policy, obs_space, action_space, config):
+    LearningRateSchedule.__init__(policy, config["lr"], config["lr_schedule"])
+    ValueNetworkMixin.__init__(policy)
 
-    @override(TFPolicy)
-    def gradients(self, optimizer, loss):
-        grads = tf.gradients(loss, self.var_list)
-        self.grads, _ = tf.clip_by_global_norm(grads, self.config["grad_clip"])
-        clipped_grads = list(zip(self.grads, self.var_list))
-        return clipped_grads
 
-    @override(TFPolicy)
-    def extra_compute_grad_fetches(self):
-        return self.stats_fetches
-
-    @override(Policy)
-    def get_initial_state(self):
-        return self.model.state_init
+VTraceTFPolicy = build_tf_policy(
+    name="VTraceTFPolicy",
+    get_default_config=lambda: ray.rllib.agents.impala.impala.DEFAULT_CONFIG,
+    loss_fn=build_vtrace_loss,
+    stats_fn=stats,
+    grad_stats_fn=grad_stats,
+    postprocess_fn=postprocess_trajectory,
+    optimizer_fn=choose_optimizer,
+    gradients_fn=clip_gradients,
+    extra_action_fetches_fn=add_behaviour_logits,
+    before_init=validate_config,
+    before_loss_init=setup_mixins,
+    mixins=[LearningRateSchedule, ValueNetworkMixin],
+    get_batch_divisibility_req=lambda p: p.config["sample_batch_size"])
diff --git a/python/ray/rllib/agents/ppo/appo_policy.py b/python/ray/rllib/agents/ppo/appo_policy.py
index e5941283e..b6d3378b8 100644
--- a/python/ray/rllib/agents/ppo/appo_policy.py
+++ b/python/ray/rllib/agents/ppo/appo_policy.py
@@ -10,14 +10,12 @@ import numpy as np
 import logging
 import gym
 
-import ray
 from ray.rllib.agents.impala import vtrace
+from ray.rllib.agents.impala.vtrace_policy import _make_time_major, \
+        BEHAVIOUR_LOGITS, VTraceTFPolicy
 from ray.rllib.evaluation.postprocessing import Postprocessing
 from ray.rllib.models.action_dist import Categorical
 from ray.rllib.policy.sample_batch import SampleBatch
-from ray.rllib.policy.tf_policy_template import build_tf_policy
-from ray.rllib.policy.tf_policy import LearningRateSchedule
-from ray.rllib.utils.explained_variance import explained_variance
 from ray.rllib.evaluation.postprocessing import compute_advantages
 from ray.rllib.utils import try_import_tf
 
@@ -25,8 +23,6 @@ tf = try_import_tf()
 
 logger = logging.getLogger(__name__)
 
-BEHAVIOUR_LOGITS = "behaviour_logits"
-
 
 class PPOSurrogateLoss(object):
     """Loss used when V-trace is disabled.
@@ -163,41 +159,6 @@ class VTraceSurrogateLoss(object):
                            self.entropy * entropy_coeff)
 
 
-def _make_time_major(policy, tensor, drop_last=False):
-    """Swaps batch and trajectory axis.
-
-    Arguments:
-        policy: Policy reference
-        tensor: A tensor or list of tensors to reshape.
-        drop_last: A bool indicating whether to drop the last
-        trajectory item.
-
-    Returns:
-        res: A tensor with swapped axes or a list of tensors with
-        swapped axes.
-    """
-    if isinstance(tensor, list):
-        return [_make_time_major(policy, t, drop_last) for t in tensor]
-
-    if policy.state_in:
-        B = tf.shape(policy.seq_lens)[0]
-        T = tf.shape(tensor)[0] // B
-    else:
-        # Important: chop the tensor into batches at known episode cut
-        # boundaries. TODO(ekl) this is kind of a hack
-        T = policy.config["sample_batch_size"]
-        B = tf.shape(tensor)[0] // T
-    rs = tf.reshape(tensor, tf.concat([[B, T], tf.shape(tensor)[1:]], axis=0))
-
-    # swap B and T axes
-    res = tf.transpose(
-        rs, [1, 0] + list(range(2, 1 + int(tf.shape(tensor).shape[0]))))
-
-    if drop_last:
-        return res[:-1]
-    return res
-
-
 def build_appo_surrogate_loss(policy, batch_tensors):
     if isinstance(policy.action_space, gym.spaces.Discrete):
         is_multidiscrete = False
@@ -283,28 +244,6 @@ def build_appo_surrogate_loss(policy, batch_tensors):
     return policy.loss.total_loss
 
 
-def stats(policy, batch_tensors):
-    values_batched = _make_time_major(
-        policy, policy.value_function, drop_last=policy.config["vtrace"])
-
-    return {
-        "cur_lr": tf.cast(policy.cur_lr, tf.float64),
-        "policy_loss": policy.loss.pi_loss,
-        "entropy": policy.loss.entropy,
-        "var_gnorm": tf.global_norm(policy.var_list),
-        "vf_loss": policy.loss.vf_loss,
-        "vf_explained_var": explained_variance(
-            tf.reshape(policy.loss.value_targets, [-1]),
-            tf.reshape(values_batched, [-1])),
-    }
-
-
-def grad_stats(policy, grads):
-    return {
-        "grad_gnorm": tf.global_norm(grads),
-    }
-
-
 def postprocess_trajectory(policy,
                            sample_batch,
                            other_agent_batches=None,
@@ -337,61 +276,8 @@ def add_values_and_logits(policy):
     return out
 
 
-def validate_config(policy, obs_space, action_space, config):
-    assert config["batch_mode"] == "truncate_episodes", \
-        "Must use `truncate_episodes` batch mode with V-trace."
-
-
-def choose_optimizer(policy, config):
-    if policy.config["opt_type"] == "adam":
-        return tf.train.AdamOptimizer(policy.cur_lr)
-    else:
-        return tf.train.RMSPropOptimizer(policy.cur_lr, config["decay"],
-                                         config["momentum"], config["epsilon"])
-
-
-def clip_gradients(policy, optimizer, loss):
-    grads = tf.gradients(loss, policy.var_list)
-    policy.grads, _ = tf.clip_by_global_norm(grads, policy.config["grad_clip"])
-    clipped_grads = list(zip(policy.grads, policy.var_list))
-    return clipped_grads
-
-
-class ValueNetworkMixin(object):
-    def __init__(self):
-        self.value_function = self.model.value_function()
-        self.var_list = tf.get_collection(tf.GraphKeys.TRAINABLE_VARIABLES,
-                                          tf.get_variable_scope().name)
-
-    def value(self, ob, *args):
-        feed_dict = {
-            self.get_placeholder(SampleBatch.CUR_OBS): [ob],
-            self.seq_lens: [1]
-        }
-        assert len(args) == len(self.state_in), \
-            (args, self.state_in)
-        for k, v in zip(self.state_in, args):
-            feed_dict[k] = v
-        vf = self.get_session().run(self.value_function, feed_dict)
-        return vf[0]
-
-
-def setup_mixins(policy, obs_space, action_space, config):
-    LearningRateSchedule.__init__(policy, config["lr"], config["lr_schedule"])
-    ValueNetworkMixin.__init__(policy)
-
-
-AsyncPPOTFPolicy = build_tf_policy(
+AsyncPPOTFPolicy = VTraceTFPolicy.with_updates(
     name="AsyncPPOTFPolicy",
-    get_default_config=lambda: ray.rllib.agents.impala.impala.DEFAULT_CONFIG,
     loss_fn=build_appo_surrogate_loss,
-    stats_fn=stats,
-    grad_stats_fn=grad_stats,
     postprocess_fn=postprocess_trajectory,
-    optimizer_fn=choose_optimizer,
-    gradients_fn=clip_gradients,
-    extra_action_fetches_fn=add_values_and_logits,
-    before_init=validate_config,
-    before_loss_init=setup_mixins,
-    mixins=[LearningRateSchedule, ValueNetworkMixin],
-    get_batch_divisibility_req=lambda p: p.config["sample_batch_size"])
+    extra_action_fetches_fn=add_values_and_logits)
diff --git a/python/ray/rllib/agents/ppo/ppo.py b/python/ray/rllib/agents/ppo/ppo.py
index 6fd725a37..eea1c5361 100644
--- a/python/ray/rllib/agents/ppo/ppo.py
+++ b/python/ray/rllib/agents/ppo/ppo.py
@@ -154,9 +154,6 @@ def validate_config(config):
             "FYI: By default, the value function will not share layers "
             "with the policy model ('vf_share_layers': False).")
 
-    # auto set the model option for layer sharing
-    config["model"]["vf_share_layers"] = config["vf_share_layers"]
-
 
 PPOTrainer = build_trainer(
     name="PPO",
diff --git a/python/ray/rllib/agents/ppo/ppo_policy.py b/python/ray/rllib/agents/ppo/ppo_policy.py
index e12da8e70..1ca54d900 100644
--- a/python/ray/rllib/agents/ppo/ppo_policy.py
+++ b/python/ray/rllib/agents/ppo/ppo_policy.py
@@ -241,6 +241,11 @@ class ValueNetworkMixin(object):
         return vf[0]
 
 
+def setup_config(policy, obs_space, action_space, config):
+    # auto set the model option for layer sharing
+    config["model"]["vf_share_layers"] = config["vf_share_layers"]
+
+
 def setup_mixins(policy, obs_space, action_space, config):
     ValueNetworkMixin.__init__(policy, obs_space, action_space, config)
     KLCoeffMixin.__init__(policy, config)
@@ -255,5 +260,6 @@ PPOTFPolicy = build_tf_policy(
     extra_action_fetches_fn=vf_preds_and_logits_fetches,
     postprocess_fn=postprocess_ppo_gae,
     gradients_fn=clip_gradients,
+    before_init=setup_config,
     before_loss_init=setup_mixins,
     mixins=[LearningRateSchedule, KLCoeffMixin, ValueNetworkMixin])
diff --git a/python/ray/rllib/examples/custom_keras_model.py b/python/ray/rllib/examples/custom_keras_model.py
index ea1c5d8ff..e82dee966 100644
--- a/python/ray/rllib/examples/custom_keras_model.py
+++ b/python/ray/rllib/examples/custom_keras_model.py
@@ -93,7 +93,7 @@ class MyKerasQModel(DistributionalQModel):
 
 
 if __name__ == "__main__":
-    ray.init(local_mode=True)
+    ray.init()
     args = parser.parse_args()
     ModelCatalog.register_custom_model("keras_model", MyKerasModel)
     ModelCatalog.register_custom_model("keras_q_model", MyKerasQModel)
@@ -102,6 +102,7 @@ if __name__ == "__main__":
         stop={"episode_reward_mean": args.stop},
         config={
             "env": "CartPole-v0",
+            "num_gpus": 0,
             "model": {
                 "custom_model": "keras_q_model"
                 if args.run == "DQN" else "keras_model"
diff --git a/python/ray/rllib/models/catalog.py b/python/ray/rllib/models/catalog.py
index 62ebb691c..4d3723c82 100644
--- a/python/ray/rllib/models/catalog.py
+++ b/python/ray/rllib/models/catalog.py
@@ -23,8 +23,9 @@ from ray.rllib.models.visionnet import VisionNetwork
 from ray.rllib.models.lstm import LSTM
 from ray.rllib.models.modelv2 import ModelV2
 from ray.rllib.models.tf.tf_modelv2 import TFModelV2
-from ray.rllib.utils.annotations import DeveloperAPI, PublicAPI
 from ray.rllib.utils import try_import_tf
+from ray.rllib.utils.annotations import DeveloperAPI, PublicAPI
+from ray.rllib.utils.error import UnsupportedSpaceException
 
 tf = try_import_tf()
 
@@ -49,7 +50,7 @@ MODEL_DEFAULTS = {
     # should already match num_outputs.
     "no_final_linear": False,
     # Whether layers should be shared for the value function.
-    "vf_share_layers": False,
+    "vf_share_layers": True,
 
     # == LSTM ==
     # Whether to wrap the model with a LSTM
@@ -120,7 +121,7 @@ class ModelCatalog(object):
         config = config or MODEL_DEFAULTS
         if isinstance(action_space, gym.spaces.Box):
             if len(action_space.shape) > 1:
-                raise ValueError(
+                raise UnsupportedSpaceException(
                     "Action space has multiple dimensions "
                     "{}. ".format(action_space.shape) +
                     "Consider reshaping this into a single dimension, "
diff --git a/python/ray/rllib/policy/tf_policy_template.py b/python/ray/rllib/policy/tf_policy_template.py
index 7419240f4..fde6cefb3 100644
--- a/python/ray/rllib/policy/tf_policy_template.py
+++ b/python/ray/rllib/policy/tf_policy_template.py
@@ -140,6 +140,7 @@ def build_tf_policy(name,
                 action_sampler_fn=action_sampler_fn,
                 existing_model=existing_model,
                 existing_inputs=existing_inputs,
+                get_batch_divisibility_req=get_batch_divisibility_req,
                 obs_include_prev_action_reward=obs_include_prev_action_reward)
 
             if after_init:
diff --git a/python/ray/rllib/tests/test_supported_spaces.py b/python/ray/rllib/tests/test_supported_spaces.py
index a7f4976ef..b091776fa 100644
--- a/python/ray/rllib/tests/test_supported_spaces.py
+++ b/python/ray/rllib/tests/test_supported_spaces.py
@@ -17,6 +17,10 @@ from ray.tune.registry import register_env
 ACTION_SPACES_TO_TEST = {
     "discrete": Discrete(5),
     "vector": Box(-1.0, 1.0, (5, ), dtype=np.float32),
+    "vector2": Box(-1.0, 1.0, (
+        5,
+        5,
+    ), dtype=np.float32),
     "multidiscrete": MultiDiscrete([1, 2, 3, 4]),
     "tuple": Tuple(
         [Discrete(2),
@@ -63,6 +67,8 @@ def make_stub_env(action_space, obs_space, check_action_bounds):
 
 
 def check_support(alg, config, stats, check_bounds=False, name=None):
+    covered_a = set()
+    covered_o = set()
     for a_name, action_space in ACTION_SPACES_TO_TEST.items():
         for o_name, obs_space in OBSERVATION_SPACES_TO_TEST.items():
             print("=== Testing", alg, action_space, obs_space, "===")
@@ -71,8 +77,13 @@ def check_support(alg, config, stats, check_bounds=False, name=None):
             stat = "ok"
             a = None
             try:
-                a = get_agent_class(alg)(config=config, env="stub_env")
-                a.train()
+                if a_name in covered_a and o_name in covered_o:
+                    stat = "skip"  # speed up tests by avoiding full grid
+                else:
+                    a = get_agent_class(alg)(config=config, env="stub_env")
+                    a.train()
+                    covered_a.add(a_name)
+                    covered_o.add(o_name)
             except UnsupportedSpaceException:
                 stat = "unsupported"
             except Exception as e:
@@ -171,7 +182,7 @@ class ModelSupportedSpaces(unittest.TestCase):
             check_bounds=True)
         num_unexpected_errors = 0
         for (alg, a_name, o_name), stat in sorted(stats.items()):
-            if stat not in ["ok", "unsupported"]:
+            if stat not in ["ok", "unsupported", "skip"]:
                 num_unexpected_errors += 1
             print(alg, "action_space", a_name, "obs_space", o_name, "result",
                   stat)
diff --git a/python/ray/rllib/tuned_examples/atari-dist-dqn.yaml b/python/ray/rllib/tuned_examples/atari-dist-dqn.yaml
index d351e403f..94f5783ed 100644
--- a/python/ray/rllib/tuned_examples/atari-dist-dqn.yaml
+++ b/python/ray/rllib/tuned_examples/atari-dist-dqn.yaml
@@ -1,4 +1,4 @@
-basic-dqn:
+atari-dist-dqn:
     env:
         grid_search:
             - BreakoutNoFrameskip-v4