modify ModelWithAux for use with custom train steps and multi-task learning.

kauldron/train/train_step.py

@@ -185,14 +185,66 @@ class ModelWithAux(config_util.UpdateFromRootCfg):
   """Wrapper around model which also compute the summaries and metrics."""
 
   model: nn.Module = config_util.ROOT_CFG_REF.model
-  losses: Mapping[str, kd_losses.Loss] = config_util.ROOT_CFG_REF.train_losses
-  metrics: Mapping[str, kd_metrics.Metric] = (
+
+  # These fields are configured via the root config, which is the common
+  # approach.
+  root_losses: Mapping[str, kd_losses.Loss] = (
+      config_util.ROOT_CFG_REF.train_losses
+  )
+  root_metrics: Mapping[str, kd_metrics.Metric] = (
       config_util.ROOT_CFG_REF.train_metrics
   )
-  summaries: Mapping[str, kd_summaries.Summary] = (
+  root_summaries: Mapping[str, kd_summaries.Summary] = (
       config_util.ROOT_CFG_REF.train_summaries
   )
 
+  # These fields are configured via any custom calls to ModelWithAux, e.g. a
+  # multi-task setup where different ModelWithAux may have different losses.
+  # These will override any matching keys in the root.
+  local_losses: Mapping[str, kd_losses.Loss] = dataclasses.field(
+      default_factory=flax.core.FrozenDict
+  )
+  local_metrics: Mapping[str, kd_metrics.Metric] = dataclasses.field(
+      default_factory=flax.core.FrozenDict
+  )
+  local_summaries: Mapping[str, kd_summaries.Summary] = dataclasses.field(
+      default_factory=flax.core.FrozenDict
+  )
+
+  def __init__(
+      self,
+      model: Optional[nn.Module] = None,
+      losses: Optional[Mapping[str, kd_losses.Loss]] = None,
+      metrics: Optional[Mapping[str, kd_metrics.Metric]] = None,
+      summaries: Optional[Mapping[str, kd_summaries.Summary]] = None,
+  ):
+    if model is not None:
+      self.model = model
+    if losses is not None:
+      self.local_losses = flax.core.FrozenDict(losses)
+    if metrics is not None:
+      self.local_metrics = flax.core.FrozenDict(metrics)
+    if summaries is not None:
+      self.local_summaries = flax.core.FrozenDict(summaries)
+
+  @property
+  def losses(self) -> Mapping[str, kd_losses.Loss]:
+    return flax.core.FrozenDict(
+        dict(self.root_losses) | dict(self.local_losses)
+    )
+
+  @property
+  def metrics(self) -> Mapping[str, kd_metrics.Metric]:
+    return flax.core.FrozenDict(
+        dict(self.root_metrics) | dict(self.local_metrics)
+    )
+
+  @property
+  def summaries(self) -> Mapping[str, kd_summaries.Summary]:
+    return flax.core.FrozenDict(
+        dict(self.root_summaries) | dict(self.local_summaries)
+    )
+
   def init(  # pylint:disable=missing-function-docstring
       self,
       init_rngs: rngs_lib.Rngs,