model <> node 2/n: Add transition edges property to GenerationNode (#…

…2446)

Summary:
Pull Request resolved: #2446

As part of modifying the generation node dag we want to support multiple transition edges now (meaning one node x could transition either to node y or node z depending on what criterion are met). This property creates a dict with {'next_node_name': [tc]} where tc is the transition criterion to move the gs from the current node to the `next node`

The reason we need this, is currently and in any future i can envision, to transition to another node all criterion for that edge that are transition blocking must be met. In the next diff I modify the should_transition method. I just like bite sized diffs :)

Reviewed By: lena-kashtelyan

Differential Revision: D57127974

fbshipit-source-id: 198f8cc4a4875a36100a2d8561bdc9d9c4ac0e1f

ax/modelbridge/generation_node.py

@@ -8,6 +8,8 @@
 
 from __future__ import annotations
 
+from collections import defaultdict
+
 from dataclasses import dataclass, field
 from logging import Logger
 from typing import Any, Callable, Dict, List, Optional, Sequence, Set, Tuple, Union
@@ -153,7 +155,7 @@ def generation_strategy(self) -> modelbridge.generation_strategy.GenerationStrat
         """Returns a backpointer to the GenerationStrategy, useful for obtaining the
         experiment associated with this GenerationStrategy"""
         # TODO: @mgarrard remove this property once we make experiment a required
-        # arguement on GenerationStrategy
+        # argument on GenerationStrategy
         if self._generation_strategy is None:
             raise ValueError(
                 "Generation strategy has not been initialized on this node."
@@ -296,7 +298,7 @@ def gen(
                     )
         assert generator_run is not None, (
             "The GeneratorRun is None which is an unexpected state of this"
-            " GenerationStrategy. This occured on GenerationNode: {self.node_name}."
+            " GenerationStrategy. This occurred on GenerationNode: {self.node_name}."
         )
         generator_run._generation_node_name = self.node_name
         return generator_run
@@ -397,6 +399,27 @@ def node_that_generated_last_gr(self) -> Optional[str]:
             else None
         )
 
+    @property
+    def transition_edges(self) -> Dict[str, List[TransitionCriterion]]:
+        """Returns a dictionary mapping the next ```GenerationNode``` to the
+        TransitionCriteria that define the transition that that node.
+
+        Ex: if the transition from the current node to node x is defined by MaxTrials
+        and MinTrials criterion then the return would be {'x': [MaxTrials, MinTrials]}.
+
+        Returns:
+            Dict[str, List[TransitionCriterion]]: A dictionary mapping the next
+            ```GenerationNode``` to the ```TransitionCriterion``` that are associated
+            with it.
+        """
+        if self.transition_criteria is None:
+            return {}
+
+        tc_edges = defaultdict(list)
+        for tc in self.transition_criteria:
+            tc_edges[tc.transition_to].append(tc)
+        return tc_edges
+
     def should_transition_to_next_node(
         self, raise_data_required_error: bool = True
     ) -> Tuple[bool, Optional[str]]:
@@ -409,7 +432,8 @@ def should_transition_to_next_node(
                 check how many generator runs (to be made into trials) can be produced,
                 but not actually producing them yet.
         Returns:
-            bool: Whether we should transition to the next node.
+            Tuple[bool, Optional[str]]: Whether we should transition to the next node
+                and the name of the next node.
         """
         # if no transition criteria are defined, this node can generate unlimited trials
         if len(self.transition_criteria) == 0:

ax/modelbridge/tests/test_generation_strategy.py

@@ -1029,7 +1029,7 @@ def test_gen_for_multiple_trials_with_multiple_models_with_fixed_features(
 
     # ---------- Tests for GenerationStrategies composed of GenerationNodes --------
     def test_gs_setup_with_nodes(self) -> None:
-        """Test GS initalization and validation with nodes"""
+        """Test GS initialization and validation with nodes"""
         node_1_criterion = [
             MaxTrials(
                 threshold=4,
@@ -1280,6 +1280,61 @@ def test_generation_strategy_eq_no_print(self) -> None:
         gs2 = self.basic_sobol_gpei_gs
         self.assertEqual(gs1, gs2)
 
+    def test_transition_edges(self) -> None:
+        """Test transition_edges property of ``GenerationNode``"""
+        # this gs has a single sobol node which transitions to gpei. If the MaxTrials
+        # and MinTrials criterion are met, the transition to sobol_2 should occur,
+        # otherwise, should transition back to sobol.
+        gpei_to_sobol2_max = MaxTrials(
+            threshold=2,
+            transition_to="sobol_2",
+            block_transition_if_unmet=True,
+            only_in_statuses=[TrialStatus.RUNNING],
+        )
+        gpei_to_sobol2_min = MinTrials(
+            threshold=1,
+            transition_to="sobol_2",
+            block_transition_if_unmet=True,
+            only_in_statuses=[TrialStatus.COMPLETED],
+        )
+        gpei_to_sobol_auto = AutoTransitionAfterGenCriterion(transition_to="sobol")
+        gs = GenerationStrategy(
+            nodes=[
+                GenerationNode(
+                    node_name="sobol",
+                    model_specs=[self.sobol_model_spec],
+                    transition_criteria=self.single_running_trial_criterion,
+                ),
+                GenerationNode(
+                    node_name="gpei",
+                    model_specs=[self.gpei_model_spec],
+                    transition_criteria=[
+                        gpei_to_sobol2_max,
+                        gpei_to_sobol2_min,
+                        gpei_to_sobol_auto,
+                    ],
+                ),
+                GenerationNode(
+                    node_name="sobol_2",
+                    model_specs=[self.sobol_model_spec],
+                ),
+            ],
+        )
+        exp = get_branin_experiment()
+        self.assertEqual(
+            gs._curr.transition_edges, {"gpei": self.single_running_trial_criterion}
+        )
+        exp.new_trial(generator_run=gs.gen(exp)).run()
+        gs.gen(exp)
+        self.assertEqual(gs.current_node_name, "gpei")
+        self.assertEqual(
+            gs._curr.transition_edges,
+            {
+                "sobol_2": [gpei_to_sobol2_max, gpei_to_sobol2_min],
+                "sobol": [gpei_to_sobol_auto],
+            },
+        )
+
     def test_node_gs_with_auto_transitions(self) -> None:
         """Test that node-based generation strategies which leverage
         AutoTransitionAfterGen criterion correctly transition and create trials.