Add a joint memory loader capable of sampling data from multiple memo…

…ry loaders (#181)

This PR adds a `JointMemoryLoader` object that can sample data from
multiple different `MemoryLoader`s. This is needed for a lot of
imitation related training.

emote/memory/memory.py

@@ -7,6 +7,7 @@
 """
 from __future__ import annotations
 
+import collections
 import inspect
 import logging
 import os
@@ -486,6 +487,57 @@ def __iter__(self):
             yield {self.data_group: data, self.size_key: data[self.size_key]}
 
 
+class JointMemoryLoader:
+    """A memory loader capable of loading data from multiple `MemoryLoader`s."""
+
+    def __init__(self, loaders: list[MemoryLoader], size_key: str = "batch_size"):
+        self._loaders = loaders
+        self._size_key = size_key
+
+        counts = collections.Counter((loader.data_group for loader in loaders))
+        counts_over_1 = {k: count for k, count in counts.items() if count > 1}
+        if len(counts_over_1) != 0:
+            raise ValueError(
+                f"""JointMemoryLoader was provided MemoryLoaders that share the same datagroup. This will clobber the joint output data and is not allowed.
+                Here is a dict of each datagroup encountered more than once, and its occurance count: {counts_over_1}"""
+            )
+
+    def is_ready(self):
+        return all(loader.is_ready() for loader in self._loaders)
+
+    def __iter__(self):
+        if not self.is_ready():
+            raise RuntimeError(
+                """memory loader(s) in JointMemoryLoader does not have enough data. Check `is_ready()`
+                before trying to iterate over data."""
+            )
+
+        while True:
+            out = {self._size_key: 0}
+
+            for loader in self._loaders:
+                data = next(iter(loader))
+                out[loader.data_group] = data[loader.data_group]
+                # for joint memory loaders we sum up all individual loader sizes
+                out[self._size_key] += data[loader.size_key]
+
+            yield out
+
+
+class JointMemoryLoaderWithDataGroup(JointMemoryLoader):
+    """A JointMemoryLoader that places its data inside of a user-specified datagroup."""
+
+    def __init__(self, loaders: list[MemoryLoader], data_group: str, size_key: str = "batch_size"):
+        super().__init__(loaders, size_key)
+        self._data_group = data_group
+
+    def __iter__(self):
+        data = next(super().__iter__())
+        total_size = data.pop(self._size_key)
+
+        yield {self._data_group: data, self._size_key: total_size}
+
+
 class MemoryWarmup(Callback):
     """A blocker to ensure memory has data.
 

tests/test_memory_loading.py

@@ -0,0 +1,123 @@
+import numpy as np
+import pytest
+
+from emote.memory.column import Column
+from emote.memory.fifo_strategy import FifoEjectionStrategy
+from emote.memory.memory import JointMemoryLoader, JointMemoryLoaderWithDataGroup, MemoryLoader
+from emote.memory.table import ArrayTable
+from emote.memory.uniform_strategy import UniformSampleStrategy
+
+
+@pytest.fixture
+def a_dummy_table():
+    tab = ArrayTable(
+        columns=[Column("state", (), np.float32), Column("action", (), np.float32)],
+        maxlen=1_000,
+        sampler=UniformSampleStrategy(),
+        ejector=FifoEjectionStrategy(),
+        length_key="action",
+        device="cpu",
+    )
+    tab.add_sequence(
+        0,
+        {
+            "state": [5.0, 6.0],
+            "action": [1.0],
+        },
+    )
+
+    return tab
+
+
+@pytest.fixture
+def another_dummy_table():
+    tab = ArrayTable(
+        columns=[Column("state", (), np.float32), Column("action", (), np.float32)],
+        maxlen=1_000,
+        sampler=UniformSampleStrategy(),
+        ejector=FifoEjectionStrategy(),
+        length_key="action",
+        device="cpu",
+    )
+    tab.add_sequence(
+        0,
+        {
+            "state": [5.0, 6.0],
+            "action": [1.0],
+        },
+    )
+
+    return tab
+
+
+def test_joint_memory_loader(a_dummy_table: ArrayTable, another_dummy_table: ArrayTable):
+    a_loader = MemoryLoader(
+        table=a_dummy_table,
+        rollout_count=1,
+        rollout_length=1,
+        size_key="batch_size",
+        data_group="a",
+    )
+    another_loader = MemoryLoader(
+        table=another_dummy_table,
+        rollout_count=1,
+        rollout_length=1,
+        size_key="batch_size",
+        data_group="another",
+    )
+
+    joint_loader = JointMemoryLoader(loaders=[a_loader, another_loader])
+
+    data = next(iter(joint_loader))
+    assert "a" in data and "another" in data, "JointMemoryLoader did not yield expected memory data"
+
+
+def test_joint_memory_loader_datagroup(a_dummy_table: ArrayTable, another_dummy_table: ArrayTable):
+    a_loader = MemoryLoader(
+        table=a_dummy_table,
+        rollout_count=1,
+        rollout_length=1,
+        size_key="batch_size",
+        data_group="a",
+    )
+    another_loader = MemoryLoader(
+        table=another_dummy_table,
+        rollout_count=1,
+        rollout_length=1,
+        size_key="batch_size",
+        data_group="another",
+    )
+
+    joint_loader = JointMemoryLoaderWithDataGroup(
+        loaders=[a_loader, another_loader], data_group="joint_datagroup"
+    )
+
+    encapsulated_data = next(iter(joint_loader))
+    data = encapsulated_data["joint_datagroup"]
+
+    assert (
+        "joint_datagroup" in encapsulated_data
+    ), "Expected joint dataloader to place data in its own datagroup, but it does not exist."
+    assert (
+        "a" in data and "another" in data
+    ), "Expected joint dataloader to actually place data in its datagroup, but it is empty."
+
+
+def test_joint_memory_loader_nonunique_loaders_trigger_exception(a_dummy_table: ArrayTable):
+    loader1 = MemoryLoader(
+        table=a_dummy_table,
+        rollout_count=1,
+        rollout_length=1,
+        size_key="batch_size",
+        data_group="a",
+    )
+    loader2 = MemoryLoader(
+        table=a_dummy_table,
+        rollout_count=1,
+        rollout_length=1,
+        size_key="batch_size",
+        data_group="a",
+    )
+
+    with pytest.raises(Exception, match="JointMemoryLoader"):
+        joint_loader = JointMemoryLoader([loader1, loader2])  # noqa