Support to convert albert tf1 ckpt to tf2's BertPretrainerV2

PiperOrigin-RevId: 335226408

official/nlp/albert/tf2_albert_encoder_checkpoint_converter.py

@@ -17,20 +17,16 @@
 The conversion will yield an object-oriented checkpoint that can be used
 to restore an AlbertEncoder object.
 """
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-
 import os
 
-# Import libraries
 from absl import app
 from absl import flags
 
 import tensorflow as tf
-from official.modeling import activations
+from official.modeling import tf_utils
 from official.nlp.albert import configs
 from official.nlp.bert import tf1_checkpoint_converter_lib
+from official.nlp.modeling import models
 from official.nlp.modeling import networks
 
 FLAGS = flags.FLAGS
@@ -47,6 +43,10 @@ flags.DEFINE_string("checkpoint_model_name", "encoder",
                     "The name of the model when saving the checkpoint, i.e., "
                     "the checkpoint will be saved using: "
                     "tf.train.Checkpoint(FLAGS.checkpoint_model_name=model).")
+flags.DEFINE_enum(
+    "converted_model", "encoder", ["encoder", "pretrainer"],
+    "Whether to convert the checkpoint to a `AlbertEncoder` model or a "
+    "`BertPretrainerV2` model (with mlm but without classification heads).")
 
 
 ALBERT_NAME_REPLACEMENTS = (
@@ -60,10 +60,10 @@ ALBERT_NAME_REPLACEMENTS = (
     ("group_0/inner_group_0/", ""),
     ("attention_1/self", "self_attention"),
     ("attention_1/output/dense", "self_attention/attention_output"),
-    ("LayerNorm/", "self_attention_layer_norm/"),
+    ("transformer/LayerNorm/", "transformer/self_attention_layer_norm/"),
     ("ffn_1/intermediate/dense", "intermediate"),
     ("ffn_1/intermediate/output/dense", "output"),
-    ("LayerNorm_1/", "output_layer_norm/"),
+    ("transformer/LayerNorm_1/", "transformer/output_layer_norm/"),
     ("pooler/dense", "pooler_transform"),
     ("cls/predictions/output_bias", "cls/predictions/output_bias/bias"),
     ("cls/seq_relationship/output_bias", "predictions/transform/logits/bias"),
@@ -73,10 +73,10 @@ ALBERT_NAME_REPLACEMENTS = (
 
 
 def _create_albert_model(cfg):
-  """Creates a BERT keras core model from BERT configuration.
+  """Creates an ALBERT keras core model from BERT configuration.
 
   Args:
-    cfg: A `BertConfig` to create the core model.
+    cfg: A `AlbertConfig` to create the core model.
 
   Returns:
     A keras model.
@@ -88,7 +88,7 @@ def _create_albert_model(cfg):
       num_layers=cfg.num_hidden_layers,
       num_attention_heads=cfg.num_attention_heads,
       intermediate_size=cfg.intermediate_size,
-      activation=activations.gelu,
+      activation=tf_utils.get_activation(cfg.hidden_act),
       dropout_rate=cfg.hidden_dropout_prob,
       attention_dropout_rate=cfg.attention_probs_dropout_prob,
       max_sequence_length=cfg.max_position_embeddings,
@@ -98,8 +98,27 @@ def _create_albert_model(cfg):
   return albert_encoder
 
 
+def _create_pretrainer_model(cfg):
+  """Creates a pretrainer with AlbertEncoder from ALBERT configuration.
+
+  Args:
+    cfg: A `BertConfig` to create the core model.
+
+  Returns:
+    A BertPretrainerV2 model.
+  """
+  albert_encoder = _create_albert_model(cfg)
+  pretrainer = models.BertPretrainerV2(
+      encoder_network=albert_encoder,
+      mlm_activation=tf_utils.get_activation(cfg.hidden_act),
+      mlm_initializer=tf.keras.initializers.TruncatedNormal(
+          stddev=cfg.initializer_range))
+  return pretrainer
+
+
 def convert_checkpoint(bert_config, output_path, v1_checkpoint,
-                       checkpoint_model_name):
+                       checkpoint_model_name,
+                       converted_model="encoder"):
   """Converts a V1 checkpoint into an OO V2 checkpoint."""
   output_dir, _ = os.path.split(output_path)
 
@@ -115,7 +134,13 @@ def convert_checkpoint(bert_config, output_path, v1_checkpoint,
       exclude_patterns=["adam", "Adam"])
 
   # Create a V2 checkpoint from the temporary checkpoint.
+  if converted_model == "encoder":
     model = _create_albert_model(bert_config)
+  elif converted_model == "pretrainer":
+    model = _create_pretrainer_model(bert_config)
+  else:
+    raise ValueError("Unsupported converted_model: %s" % converted_model)
+
   tf1_checkpoint_converter_lib.create_v2_checkpoint(model, temporary_checkpoint,
                                                     output_path,
                                                     checkpoint_model_name)
@@ -132,9 +157,11 @@ def main(_):
   output_path = FLAGS.converted_checkpoint_path
   v1_checkpoint = FLAGS.checkpoint_to_convert
   checkpoint_model_name = FLAGS.checkpoint_model_name
+  converted_model = FLAGS.converted_model
   albert_config = configs.AlbertConfig.from_json_file(FLAGS.albert_config_file)
   convert_checkpoint(albert_config, output_path, v1_checkpoint,
-                     checkpoint_model_name)
+                     checkpoint_model_name,
+                     converted_model=converted_model)
 
 
 if __name__ == "__main__":