Sample Batches¶

SampleBatch (ray.rllib.policy.sample_batch.SampleBatch)¶

Whether running in a single process or large cluster, all data interchange in RLlib happens in the form of RolloutWorker collects batches of size rollout_fragment_length, and RLlib then concatenates one or more of these batches (across different RolloutWorker in subsequent sampling steps) into a batch of size train_batch_size, which then serves as the input to a Policy’s learn_on_batch() method.

A typical sample batch looks something like the following when summarized. Since all values are kept in arrays, this allows for efficient encoding and transmission across the network:

{ 'action_logp': np.ndarray((200,), dtype=float32, min=-0.701, max=-0.685, mean=-0.694),
  'actions': np.ndarray((200,), dtype=int64, min=0.0, max=1.0, mean=0.495),
  'dones': np.ndarray((200,), dtype=bool, min=0.0, max=1.0, mean=0.055),
  'infos': np.ndarray((200,), dtype=object, head={}),
  'new_obs': np.ndarray((200, 4), dtype=float32, min=-2.46, max=2.259, mean=0.018),
  'obs': np.ndarray((200, 4), dtype=float32, min=-2.46, max=2.259, mean=0.016),
  'rewards': np.ndarray((200,), dtype=float32, min=1.0, max=1.0, mean=1.0),
  't': np.ndarray((200,), dtype=int64, min=0.0, max=34.0, mean=9.14)}

class ray.rllib.policy.sample_batch.SampleBatch(*args, **kwargs)[source]¶

Wrapper around a dictionary with string keys and array-like values.

For example, {“obs”: [1, 2, 3], “reward”: [0, -1, 1]} is a batch of three samples, each with an “obs” and “reward” attribute.

agent_steps() → int[source]¶

Returns the same as len(self) (number of steps in this batch).

To make this compatible with MultiAgentBatch.agent_steps().

env_steps() → int[source]¶

Returns the same as len(self) (number of steps in this batch).

To make this compatible with MultiAgentBatch.env_steps().

concat(other: ray.rllib.policy.sample_batch.SampleBatch) → ray.rllib.policy.sample_batch.SampleBatch[source]¶

Concatenates other to this one and returns a new SampleBatch.

Parameters: other – The other SampleBatch object to concat to this one.
Returns: The new SampleBatch, resulting from concating other to self.

Examples

>>> import numpy as np
>>> from ray.rllib.policy.sample_batch import SampleBatch
>>> b1 = SampleBatch({"a": np.array([1, 2])}) 
>>> b2 = SampleBatch({"a": np.array([3, 4, 5])}) 
>>> print(b1.concat(b2)) 
{"a": np.array([1, 2, 3, 4, 5])}

copy(shallow: bool = False) → ray.rllib.policy.sample_batch.SampleBatch[source]¶

Creates a deep or shallow copy of this SampleBatch and returns it.

Parameters: shallow – Whether the copying should be done shallowly.
Returns: A deep or shallow copy of this SampleBatch object.

rows() → Iterator[Dict[str, Any]][source]¶

Returns an iterator over data rows, i.e. dicts with column values.

Note that if seq_lens is set in self, we set it to 1 in the rows.

Yields: The column values of the row in this iteration.

Examples

>>> from ray.rllib.policy.sample_batch import SampleBatch
>>> batch = SampleBatch({ 
...    "a": [1, 2, 3],
...    "b": [4, 5, 6],
...    "seq_lens": [1, 2]
... })
>>> for row in batch.rows(): 
...    print(row) 
{"a": 1, "b": 4, "seq_lens": 1}
{"a": 2, "b": 5, "seq_lens": 1}
{"a": 3, "b": 6, "seq_lens": 1}

columns(keys: List[str]) → List[any][source]¶

Returns a list of the batch-data in the specified columns.

Parameters: keys – List of column names fo which to return the data.
Returns: The list of data items ordered by the order of column names in keys.

Examples

>>> from ray.rllib.policy.sample_batch import SampleBatch
>>> batch = SampleBatch({"a": [1], "b": [2], "c": [3]}) 
>>> print(batch.columns(["a", "b"])) 
[[1], [2]]

shuffle() → ray.rllib.policy.sample_batch.SampleBatch[source]¶

Shuffles the rows of this batch in-place.

Returns: This very (now shuffled) SampleBatch.
Raises: ValueError – If self[SampleBatch.SEQ_LENS] is defined.

Examples

>>> from ray.rllib.policy.sample_batch import SampleBatch
>>> batch = SampleBatch({"a": [1, 2, 3, 4]})  
>>> print(batch.shuffle()) 
{"a": [4, 1, 3, 2]}

split_by_episode() → List[ray.rllib.policy.sample_batch.SampleBatch][source]¶

Splits by eps_id column and returns list of new batches.

Returns: List of batches, one per distinct episode.
Raises: KeyError – If the eps_id AND dones columns are not present.

Examples

>>> from ray.rllib.policy.sample_batch import SampleBatch
>>> batch = SampleBatch( 
...     {"a": [1, 2, 3], "eps_id": [0, 0, 1]})
>>> print(batch.split_by_episode()) 
[{"a": [1, 2], "eps_id": [0, 0]}, {"a": [3], "eps_id": [1]}]

timeslices(size: Optional[int] = None, num_slices: Optional[int] = None, k: Optional[int] = None) → List[ray.rllib.policy.sample_batch.SampleBatch][source]¶

Returns SampleBatches, each one representing a k-slice of this one.

Will start from timestep 0 and produce slices of size=k.

Parameters

size – The size (in timesteps) of each returned SampleBatch.
num_slices – The number of slices to produce.
k – Deprecated: Use size or num_slices instead. The size (in timesteps) of each returned SampleBatch.

Returns

The list of num_slices (new) SampleBatches or n (new) SampleBatches each one of size size.

right_zero_pad(max_seq_len: int, exclude_states: bool = True)[source]¶

Right (adding zeros at end) zero-pads this SampleBatch in-place.

This will set the self.zero_padded flag to True and self.max_seq_len to the given max_seq_len value.

Parameters

max_seq_len – The max (total) length to zero pad to.
exclude_states – If False, also right-zero-pad all state_in_x data. If True, leave state_in_x keys as-is.

Returns

This very (now right-zero-padded) SampleBatch.

Raises

ValueError – If self[SampleBatch.SEQ_LENS] is None (not defined).

Examples

>>> from ray.rllib.policy.sample_batch import SampleBatch
>>> batch = SampleBatch( 
...     {"a": [1, 2, 3], "seq_lens": [1, 2]})
>>> print(batch.right_zero_pad(max_seq_len=4)) 
{"a": [1, 0, 0, 0, 2, 3, 0, 0], "seq_lens": [1, 2]}

>>> batch = SampleBatch({"a": [1, 2, 3], 
...                      "state_in_0": [1.0, 3.0],
...                      "seq_lens": [1, 2]})
>>> print(batch.right_zero_pad(max_seq_len=5)) 
{"a": [1, 0, 0, 0, 0, 2, 3, 0, 0, 0],
 "state_in_0": [1.0, 3.0],  # <- all state-ins remain as-is
 "seq_lens": [1, 2]}

to_device(device, framework='torch')[source]¶: TODO: transfer batch to given device as framework tensor.

size_bytes() → int[source]¶

Returns sum over number of bytes of all data buffers.

For numpy arrays, we use nbytes. For all other value types, we use sys.getsizeof(…).

Returns: The overall size in bytes of the data buffer (all columns).

get(key, default=None)[source]¶: Return the value for key if key is in the dictionary, else default.

as_multi_agent() → ray.rllib.policy.sample_batch.MultiAgentBatch[source]¶

Returns the respective MultiAgentBatch using DEFAULT_POLICY_ID.

Returns: The MultiAgentBatch (using DEFAULT_POLICY_ID) corresponding to this SampleBatch.

compress(bulk: bool = False, columns: Set[str] = frozenset({'new_obs', 'obs'})) → ray.rllib.policy.sample_batch.SampleBatch[source]¶

Compresses the data buffers (by column) in place.

Parameters

bulk – Whether to compress across the batch dimension (0) as well. If False will compress n separate list items, where n is the batch size.
columns – The columns to compress. Default: Only compress the obs and new_obs columns.

Returns

This very (now compressed) SampleBatch.

decompress_if_needed(columns: Set[str] = frozenset({'new_obs', 'obs'})) → ray.rllib.policy.sample_batch.SampleBatch[source]¶

Decompresses data buffers (per column if not compressed) in place.

Parameters: columns – The columns to decompress. Default: Only decompress the obs and new_obs columns.
Returns: This very (now uncompressed) SampleBatch.

get_single_step_input_dict(view_requirements: Dict[str, ViewRequirement], index: Union[str, int] = 'last') → SampleBatch[source]¶

Creates single ts SampleBatch at given index from self.

For usage as input-dict for model (action or value function) calls.

Parameters

view_requirements – A view requirements dict from the model for which to produce the input_dict.
index – An integer index value indicating the position in the trajectory for which to generate the compute_actions input dict. Set to “last” to generate the dict at the very end of the trajectory (e.g. for value estimation). Note that “last” is different from -1, as “last” will use the final NEXT_OBS as observation input.

Returns

The (single-timestep) input dict for ModelV2 calls.

MultiAgentBatch (ray.rllib.policy.sample_batch.MultiAgentBatch)¶

In multi-agent mode, several sample batches may be collected separately for each individual policy and are placed in a container object of type MultiAgentBatch:

class ray.rllib.policy.sample_batch.MultiAgentBatch(policy_batches: Dict[str, ray.rllib.policy.sample_batch.SampleBatch], env_steps: int)[source]¶

A batch of experiences from multiple agents in the environment.

policy_batches¶

Mapping from policy ids to SampleBatches of experiences.

Type: Dict[PolicyID, SampleBatch]

count¶: The number of env steps in this batch.

env_steps() → int[source]¶

The number of env steps (there are >= 1 agent steps per env step).

Returns: The number of environment steps contained in this batch.

agent_steps() → int[source]¶

The number of agent steps (there are >= 1 agent steps per env step).

Returns: The number of agent steps total in this batch.

timeslices(k: int) → List[ray.rllib.policy.sample_batch.MultiAgentBatch][source]¶

Returns k-step batches holding data for each agent at those steps.

For examples, suppose we have agent1 observations [a1t1, a1t2, a1t3], for agent2, [a2t1, a2t3], and for agent3, [a3t3] only.

Calling timeslices(1) would return three MultiAgentBatches containing [a1t1, a2t1], [a1t2], and [a1t3, a2t3, a3t3].

Calling timeslices(2) would return two MultiAgentBatches containing [a1t1, a1t2, a2t1], and [a1t3, a2t3, a3t3].

This method is used to implement “lockstep” replay mode. Note that this method does not guarantee each batch contains only data from a single unroll. Batches might contain data from multiple different envs.

static wrap_as_needed(policy_batches: Dict[str, ray.rllib.policy.sample_batch.SampleBatch], env_steps: int) → Union[ray.rllib.policy.sample_batch.SampleBatch, ray.rllib.policy.sample_batch.MultiAgentBatch][source]¶

Returns SampleBatch or MultiAgentBatch, depending on given policies. If policy_batches is empty (i.e. {}) it returns an empty MultiAgentBatch.

Parameters

policy_batches – Mapping from policy ids to SampleBatch.
env_steps – Number of env steps in the batch.

Returns

The single default policy’s SampleBatch or a MultiAgentBatch (more than one policy).

copy() → ray.rllib.policy.sample_batch.MultiAgentBatch[source]¶

Deep-copies self into a new MultiAgentBatch.

Returns: The copy of self with deep-copied data.

size_bytes() → int[source]¶

Returns: The overall size in bytes of all policy batches (all columns).

compress(bulk: bool = False, columns: Set[str] = frozenset({'new_obs', 'obs'})) → None[source]¶

Compresses each policy batch (per column) in place.

Parameters

bulk – Whether to compress across the batch dimension (0) as well. If False will compress n separate list items, where n is the batch size.
columns – Set of column names to compress.

decompress_if_needed(columns: Set[str] = frozenset({'new_obs', 'obs'})) → ray.rllib.policy.sample_batch.MultiAgentBatch[source]¶

Decompresses each policy batch (per column), if already compressed.

Parameters: columns – Set of column names to decompress.
Returns: Self.

as_multi_agent() → ray.rllib.policy.sample_batch.MultiAgentBatch[source]¶

Simply returns self (already a MultiAgentBatch).

Returns: This very instance of MultiAgentBatch.

Ray 3.0.0.dev0

Sample Batches¶

SampleBatch (ray.rllib.policy.sample_batch.SampleBatch)¶

MultiAgentBatch (ray.rllib.policy.sample_batch.MultiAgentBatch)¶