Make BeamSearch Registrable (#5231)

* Make BeamSearch Registrable

* Update changelog

* Remove unused import

* Update CHANGELOG.md

Co-authored-by: Pete <petew@allenai.org>
Co-authored-by: Pete <epwalsh10@gmail.com>

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Renamed `sanity_checks` to `confidence_checks` (`sanity_checks` is deprecated and will be removed in AllenNLP 3.0).
 - Trainer callbacks can now store and restore state in case a training run gets interrupted.
 - VilBERT backbone now rolls and unrolls extra dimensions to handle input with > 3 dimensions.
+- `BeamSearch` is now a `Registrable` class.
 
 ### Added
 

allennlp/nn/beam_search.py

@@ -6,7 +6,7 @@
 from overrides import overrides
 import torch
 
-from allennlp.common import FromParams, Registrable
+from allennlp.common import Registrable
 from allennlp.common.checks import ConfigurationError
 from allennlp.nn.util import min_value_of_dtype
 
@@ -683,7 +683,7 @@ def _update_state(
         return state
 
 
-class BeamSearch(FromParams):
+class BeamSearch(Registrable):
     """
     Implements the beam search algorithm for decoding the most likely sequences.
 
@@ -731,6 +731,8 @@ class BeamSearch(FromParams):
         provided, no constraints will be enforced.
     """
 
+    default_implementation = "beam_search"
+
     def __init__(
         self,
         end_index: int,
@@ -1180,3 +1182,6 @@ def _update_state(self, state: StateType, backpointer: torch.Tensor):
                     .gather(1, expanded_backpointer)
                     .reshape(batch_size * self.beam_size, *last_dims)
                 )
+
+
+BeamSearch.register("beam_search")(BeamSearch)