Add possibility to evaluate every epoch (#7302)

* Add possibility to evaluate every epoch

* Remove multitype arg

* Remove needless import

* Use a proper enum

* Apply suggestions from @LysandreJik

Co-authored-by: Lysandre Debut <lysandre@huggingface.co>

* One else and formatting

Co-authored-by: Lysandre Debut <lysandre@huggingface.co>

src/transformers/training_args.py

@@ -1,10 +1,13 @@
 import dataclasses
 import json
 import os
+import warnings
 from dataclasses import dataclass, field
+from enum import Enum
 from typing import Any, Dict, List, Optional, Tuple
 
 from .file_utils import cached_property, is_torch_available, is_torch_tpu_available, torch_required
+from .trainer_utils import EvaluationStrategy
 from .utils import logging
 
 
@@ -50,8 +53,13 @@ class TrainingArguments:
             Whether to run evaluation on the dev set or not.
         do_predict (:obj:`bool`, `optional`, defaults to :obj:`False`):
             Whether to run predictions on the test set or not.
-        evaluate_during_training (:obj:`bool`, `optional`, defaults to :obj:`False`):
-            Whether to run evaluation during training at each logging step or not.
+        evaluation_strategy(:obj:`str` or :class:`~transformers.trainer_utils.EvaluationStrategy`, `optional`, defaults to :obj:`"no"`):
+            The evaluation strategy to adopt during training. Possible values are:
+
+                * :obj:`"no"`: No evaluation is done during training.
+                * :obj:`"steps"`: Evaluation is done (and logged) every :obj:`eval_steps`.
+                * :obj:`"epoch"`: Evaluation is done at the end of each epoch.
+
         prediction_loss_only (:obj:`bool`, `optional`, defaults to `False`):
             When performing evaluation and predictions, only returns the loss.
         per_device_train_batch_size (:obj:`int`, `optional`, defaults to 8):
@@ -111,8 +119,9 @@ class TrainingArguments:
         dataloader_drop_last (:obj:`bool`, `optional`, defaults to :obj:`False`):
             Whether to drop the last incomplete batch (if the length of the dataset is not divisible by the batch size)
             or not.
-        eval_steps (:obj:`int`, `optional`, defaults to 1000):
-            Number of update steps between two evaluations.
+        eval_steps (:obj:`int`, `optional`):
+            Number of update steps between two evaluations if :obj:`evaluation_strategy="steps"`. Will default to the
+            same value as :obj:`logging_steps` if not set.
         past_index (:obj:`int`, `optional`, defaults to -1):
             Some models like :doc:`TransformerXL <../model_doc/transformerxl>` or :doc`XLNet <../model_doc/xlnet>` can
             make use of the past hidden states for their predictions. If this argument is set to a positive int, the
@@ -153,7 +162,11 @@ class TrainingArguments:
     do_eval: bool = field(default=False, metadata={"help": "Whether to run eval on the dev set."})
     do_predict: bool = field(default=False, metadata={"help": "Whether to run predictions on the test set."})
     evaluate_during_training: bool = field(
-        default=False,
+        default=None,
+        metadata={"help": "Run evaluation during training at each logging step."},
+    )
+    evaluation_strategy: EvaluationStrategy = field(
+        default="no",
         metadata={"help": "Run evaluation during training at each logging step."},
     )
     prediction_loss_only: bool = field(
@@ -245,7 +258,7 @@ class TrainingArguments:
     dataloader_drop_last: bool = field(
         default=False, metadata={"help": "Drop the last incomplete batch if it is not divisible by the batch size."}
     )
-    eval_steps: int = field(default=1000, metadata={"help": "Run an evaluation every X steps."})
+    eval_steps: int = field(default=None, metadata={"help": "Run an evaluation every X steps."})
 
     past_index: int = field(
         default=-1,
@@ -269,6 +282,19 @@ class TrainingArguments:
     def __post_init__(self):
         if self.disable_tqdm is None:
             self.disable_tqdm = logger.getEffectiveLevel() > logging.WARN
+        if self.evaluate_during_training is not None:
+            self.evaluation_strategy = (
+                EvaluationStrategy.STEPS if self.evaluate_during_training else EvaluationStrategy.NO
+            )
+            warnings.warn(
+                "The `evaluate_during_training` argument is deprecated in favor of `evaluation_strategy` (which has more options)",
+                FutureWarning,
+            )
+        else:
+            self.evaluation_strategy = EvaluationStrategy(self.evaluation_strategy)
+
+        if self.eval_steps is None:
+            self.eval_steps = self.logging_steps
 
     @property
     def train_batch_size(self) -> int:
@@ -347,17 +373,27 @@ class TrainingArguments:
         """
         return self._setup_devices[1]
 
+    def to_dict(self):
+        """
+        Serializes this instance while replace `Enum` by their values (for JSON serialization support).
+        """
+        d = dataclasses.asdict(self)
+        for k, v in d.items():
+            if isinstance(v, Enum):
+                d[k] = v.value
+        return d
+
     def to_json_string(self):
         """
         Serializes this instance to a JSON string.
         """
-        return json.dumps(dataclasses.asdict(self), indent=2)
+        return json.dumps(self.to_dict(), indent=2)
 
     def to_sanitized_dict(self) -> Dict[str, Any]:
         """
         Sanitized serialization to use with TensorBoard’s hparams
         """
-        d = dataclasses.asdict(self)
+        d = self.to_dict()
         d = {**d, **{"train_batch_size": self.train_batch_size, "eval_batch_size": self.eval_batch_size}}
 
         valid_types = [bool, int, float, str]