Support explicit_chunk for mode-choice components

activitysim/abm/models/trip_mode_choice.py

@@ -228,6 +228,7 @@ def trip_mode_choice(
             trace_choice_name="trip_mode_choice",
             estimator=estimator,
             compute_settings=model_settings.compute_settings,
+            explicit_chunk_size=model_settings.explicit_chunk,
         )
 
         if state.settings.trace_hh_id:

activitysim/abm/models/util/mode.py

@@ -36,6 +36,7 @@ def mode_choice_simulate(
     trace_column_names=None,
     estimator: Optional[Estimator] = None,
     compute_settings: ComputeSettings | None = None,
+    explicit_chunk_size: float = 0,
 ):
     """
     common method for  both tour_mode_choice and trip_mode_choice
@@ -47,13 +48,15 @@ def mode_choice_simulate(
     nest_spec
     skims
     locals_d
-    chunk_size
     mode_column_name
     logsum_column_name
     trace_label
     trace_choice_name
     estimator
-    compute_settings : ComputeSettings
+    compute_settings : ComputeSettings, optional
+    explicit_chunk_size : float, default 0
+        If > 0, the fixed number of choosers per chunk (explicit chunking); if 0, chunk sizing
+        follows the run's chunk_training_mode / adaptive sizing.
 
     Returns
     -------
@@ -74,6 +77,7 @@ def mode_choice_simulate(
         estimator=estimator,
         trace_column_names=trace_column_names,
         compute_settings=compute_settings,
+        explicit_chunk_size=explicit_chunk_size,
     )
 
     # for consistency, always return dataframe, whether or not logsums were requested
@@ -176,6 +180,7 @@ def run_tour_mode_choice_simulate(
         trace_column_names=trace_column_names,
         estimator=estimator,
         compute_settings=model_settings.compute_settings,
+        explicit_chunk_size=model_settings.explicit_chunk,
     )
 
     return choices

activitysim/core/configuration/logit.py

@@ -200,6 +200,14 @@ class TemplatedLogitComponentSettings(LogitComponentSettings, extra="forbid"):
     segment-specific names.
     """
 
+    explicit_chunk: float = 0
+    """
+    If > 0, use this fixed chunk size (number of chooser rows) instead of adaptive
+    chunking. If less than 1, use this fraction of the total number of rows. Plumbed
+    through mode_choice_simulate -> simple_simulate so mode-choice models can be chunked
+    (default 0 = unchanged chunkless/adaptive behavior).
+    """
+
 
 class LocationComponentSettings(BaseLogitComponentSettings):
     """

activitysim/core/simulate.py

@@ -1846,6 +1846,7 @@ def simple_simulate(
     trace_choice_name=None,
     trace_column_names=None,
     compute_settings: ComputeSettings | None = None,
+    explicit_chunk_size: float = 0,
 ):
     """
     Run an MNL or NL simulation for when the model spec does not involve alternative
@@ -1864,7 +1865,9 @@ def simple_simulate(
         chooser_chunk,
         chunk_trace_label,
         chunk_sizer,
-    ) in chunk.adaptive_chunked_choosers(state, choosers, trace_label):
+    ) in chunk.adaptive_chunked_choosers(
+        state, choosers, trace_label, explicit_chunk_size=explicit_chunk_size
+    ):
         choices = _simple_simulate(
             state,
             chooser_chunk,