Added SFT Pre-Processing for Grain Input Pipeline

src/maxtext/input_pipeline/data_processing_utils.py

@@ -0,0 +1,146 @@
+# Copyright 2023–2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utility functions for data processing pipelines."""
+
+import functools
+
+import jax
+from grain.experimental import BestFitPackIterDataset, pick_performance_config
+import grain.python as grain
+
+from maxtext.input_pipeline import input_pipeline_utils
+from maxtext.input_pipeline import tokenizer
+
+
+def parse_and_keep_features(dataset, config, data_columns, tokenize):
+  """Parse arrayrecord features or keep specified columns for other formats."""
+  if config.grain_file_type == "arrayrecord":
+    dataset = dataset.map(input_pipeline_utils.ParseFeatures(data_columns, tokenize))
+    dataset = dataset.map(input_pipeline_utils.NormalizeFeatures(data_columns, tokenize))
+  else:
+    dataset = dataset.map(input_pipeline_utils.KeepFeatures(feature_names=data_columns))
+  return dataset
+
+
+def get_tokenizer_and_pad_id(config):
+  """Builds tokenizer and extracts pad_id safely."""
+  tokenizer_model = tokenizer.build_tokenizer(
+      config.tokenizer_path,
+      config.tokenizer_type,
+      config.add_bos,
+      config.add_eos,
+      config.hf_access_token,
+  )
+  if tokenizer_model.pad_id is not None:
+    pad_id = tokenizer_model.pad_id
+  elif tokenizer_model.unk_id is not None:
+    pad_id = tokenizer_model.unk_id
+  else:
+    pad_id = 0
+  return tokenizer_model, pad_id
+
+
+def validate_and_configure_sft_columns(data_columns, tokenizer_model, chat_template=None):
+  """Validates SFT data columns and configures the tokenizer chat template."""
+  if chat_template and hasattr(tokenizer_model, "chat_template"):
+    tokenizer_model.chat_template = chat_template
+
+  supported_columns = [["prompt", "completion"], ["messages"], ["question", "answer"]]
+  assert any(
+      set(data_columns) == set(supported) for supported in supported_columns
+  ), f"Dataset column names mismatch. Expected columns to match one of {supported_columns}, but got {data_columns}"
+
+
+def get_local_batch_size(config):
+  """Computes local batch size based on process count and expansion factor."""
+  batch_size = config.global_batch_size_to_load // jax.process_count()
+  if config.expansion_factor_real_data > 1:
+    # global_batch_size_to_load has been expanded in pyconfig.py when expansion_factor_real_data > 1.
+    # But when using Grain, we want to keep the batch_size consistent with that in the checkpoint.
+    # We revert the batch_size expansion here, but load multiple batches per step in multihost_dataloading.py.
+    batch_size = int(batch_size // config.expansion_factor_real_data)
+  return batch_size
+
+
+def format_and_batch(dataset, config, batch_size, pad_id, data_columns, tokenizer_model):
+  """Packs or pads the dataset according to config and batches it."""
+  if config.packing:
+    length_struct = {col: config.max_target_length for col in data_columns}
+    max_segments = config.max_segments_per_seq
+    if max_segments is not None and max_segments <= 0:
+      max_segments = None
+    if config.grain_packing_type == "first_fit":
+      dataset = grain.experimental.FirstFitPackIterDataset(
+          dataset,
+          length_struct=length_struct,
+          num_packing_bins=batch_size,
+          max_sequences_per_bin=max_segments,
+      )
+    elif config.grain_packing_type == "best_fit":
+      dataset = BestFitPackIterDataset(dataset, length_struct=length_struct, num_packing_bins=batch_size)
+    elif config.grain_packing_type == "concat_then_split":
+      if config.add_bos and hasattr(tokenizer_model, "bos_id"):
+        dataset = grain.experimental.ConcatThenSplitIterDataset(
+            dataset,
+            length_struct=length_struct,
+            bos_handling=grain.experimental.BOSHandling.REPLACE_FIRST_TOKEN_WITH_BOS,
+            bos_token_id=tokenizer_model.bos_id,
+        )
+      else:
+        dataset = grain.experimental.ConcatThenSplitIterDataset(dataset, length_struct=length_struct)
+    else:
+      raise ValueError(f"Unknown packing type: {config.packing}")
+
+    rekey_dict = {
+        "targets_segmentation": "targets_segment_ids",
+        "inputs_segmentation": "inputs_segment_ids",
+        "targets_position": "targets_positions",
+        "inputs_position": "inputs_positions",
+    }
+    dataset = dataset.map(input_pipeline_utils.Rekey(rekey_dict))
+  else:
+    dataset = dataset.map(input_pipeline_utils.PadOrTrimToMaxLength(config.max_target_length, pad_id))
+
+  batch_fn = functools.partial(grain.experimental.batch_and_pad, batch_size=batch_size, pad_value=pad_id)
+  dataset = dataset.batch(batch_size, batch_fn=batch_fn)
+  return dataset
+
+
+def shift_dataset(dataset, pad_id):
+  """Shift tokens to create inputs and targets for standard next-token prediction."""
+  return dataset.map(
+      input_pipeline_utils.ShiftData(
+          ignored_ids=[pad_id],
+          axis=1,
+      )
+  )
+
+
+def apply_multiprocessing_and_prefetch(dataset, config, grain_worker_count, grain_per_worker_buffer_size):
+  """Applies multiprocessing and prefetching configurations to the dataset."""
+  multiprocessing_options = (
+      pick_performance_config(
+          ds=dataset,
+          ram_budget_mb=config.grain_ram_budget_mb,
+          max_workers=None,
+          max_buffer_size=None,
+      ).multiprocessing_options
+      if grain_worker_count == -1
+      else grain.MultiprocessingOptions(
+          num_workers=grain_worker_count,
+          per_worker_buffer_size=grain_per_worker_buffer_size,
+      )
+  )
+  return dataset.mp_prefetch(multiprocessing_options)