[Examples] create model with custom config on the fly (#11798)

* create custom model on the flight

* better wording

* add update_from_string

* cleanup

* cleanup

* Update src/transformers/configuration_utils.py
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* more bool options

* style

* fix logger

* add test

* add the doc

* assert on conflict of options
Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

examples/pytorch/language-modeling/README.md

@@ -161,3 +161,21 @@ concatenates all texts and then splits them in blocks of the same length).
 
 **Note:** On TPU, you should use the flag `--pad_to_max_length` in conjunction with the `--line_by_line` flag to make
 sure all your batches have the same length.
+
+
+## Creating a model on the fly
+
+When training a model from scratch, configuration values may be overridden with the help of `--config_overrides`:
+
+
+```bash
+python run_clm.py --model_type gpt2 --tokenizer_name gpt2 \ --config_overrides="n_embd=1024,n_head=16,n_layer=48,n_positions=102" \
+[...]
+```
+
+At the moment this is only available in `run_clm.py` but eventually should be copied to all other LM examples.
+
+This feature can also be used to activate gradient checkpointing by passing:
+```
+--config_overrides "gradient_checkpointing=true,use_cache=False"
+```

examples/pytorch/language-modeling/run_clm.py

@@ -75,6 +75,13 @@ class ModelArguments:
         default=None,
         metadata={"help": "If training from scratch, pass a model type from the list: " + ", ".join(MODEL_TYPES)},
     )
+    config_overrides: Optional[str] = field(
+        default=None,
+        metadata={
+            "help": "Override some existing default config settings when a model is trained from scratch. Example: "
+            "n_embd=10,resid_pdrop=0.2,scale_attn_weights=false,summary_type=cls_index"
+        },
+    )
     config_name: Optional[str] = field(
         default=None, metadata={"help": "Pretrained config name or path if not the same as model_name"}
     )
@@ -101,6 +108,12 @@ class ModelArguments:
         },
     )
 
+    def __post_init__(self):
+        if self.config_overrides is not None and (self.config_name is not None or self.model_name_or_path is not None):
+            raise ValueError(
+                "--config_overrides can't be used in combination with --config_name or --model_name_or_path"
+            )
+
 
 @dataclass
 class DataTrainingArguments:
@@ -279,6 +292,9 @@ def main():
     else:
         config = CONFIG_MAPPING[model_args.model_type]()
         logger.warning("You are instantiating a new config instance from scratch.")
+        if model_args.config_overrides is not None:
+            logger.info(f"Overriding config: {model_args.config_overrides}")
+            config.update_from_string(model_args.config_overrides)
 
     tokenizer_kwargs = {
         "cache_dir": model_args.cache_dir,
@@ -306,8 +322,9 @@ def main():
             use_auth_token=True if model_args.use_auth_token else None,
         )
     else:
-        logger.info("Training new model from scratch")
         model = AutoModelForCausalLM.from_config(config)
+        n_params = sum(dict((p.data_ptr(), p.numel()) for p in model.parameters()).values())
+        logger.info(f"Training new model from scratch - Total size={n_params/2**20:.2f}M params")
 
     model.resize_token_embeddings(len(tokenizer))
 

src/transformers/configuration_utils.py

@@ -667,7 +667,45 @@ class PretrainedConfig(PushToHubMixin):
         Updates attributes of this class with attributes from ``config_dict``.
 
         Args:
-            config_dict (:obj:`Dict[str, Any]`): Dictionary of attributes that shall be updated for this class.
+            config_dict (:obj:`Dict[str, Any]`): Dictionary of attributes that should be updated for this class.
         """
         for key, value in config_dict.items():
             setattr(self, key, value)
+
+    def update_from_string(self, update_str: str):
+        """
+        Updates attributes of this class with attributes from ``update_str``.
+
+        The expected format is ints, floats and strings as is, and for booleans use ``true`` or ``false``. For example:
+        "n_embd=10,resid_pdrop=0.2,scale_attn_weights=false,summary_type=cls_index"
+
+        The keys to change have to already exist in the config object.
+
+        Args:
+            update_str (:obj:`str`): String with attributes that should be updated for this class.
+
+        """
+
+        d = dict(x.split("=") for x in update_str.split(","))
+        for k, v in d.items():
+            if not hasattr(self, k):
+                raise ValueError(f"key {k} isn't in the original config dict")
+
+            old_v = getattr(self, k)
+            if isinstance(old_v, bool):
+                if v.lower() in ["true", "1", "y", "yes"]:
+                    v = True
+                elif v.lower() in ["false", "0", "n", "no"]:
+                    v = False
+                else:
+                    raise ValueError(f"can't derive true or false from {v} (key {k})")
+            elif isinstance(old_v, int):
+                v = int(v)
+            elif isinstance(old_v, float):
+                v = float(v)
+            elif not isinstance(old_v, str):
+                raise ValueError(
+                    f"You can only update int, float, bool or string values in the config, got {v} for key {k}"
+                )
+
+            setattr(self, k, v)

tests/test_configuration_common.py

@@ -21,7 +21,7 @@ import unittest
 
 from huggingface_hub import HfApi
 from requests.exceptions import HTTPError
-from transformers import BertConfig
+from transformers import BertConfig, GPT2Config
 from transformers.testing_utils import ENDPOINT_STAGING, PASS, USER, is_staging_test
 
 
@@ -138,3 +138,21 @@ class ConfigPushToHubTester(unittest.TestCase):
             for k, v in config.__dict__.items():
                 if k != "transformers_version":
                     self.assertEqual(v, getattr(new_config, k))
+
+
+class ConfigTestUtils(unittest.TestCase):
+    def test_config_from_string(self):
+        c = GPT2Config()
+
+        # attempt to modify each of int/float/bool/str config records and verify they were updated
+        n_embd = c.n_embd + 1  # int
+        resid_pdrop = c.resid_pdrop + 1.0  # float
+        scale_attn_weights = not c.scale_attn_weights  # bool
+        summary_type = c.summary_type + "foo"  # str
+        c.update_from_string(
+            f"n_embd={n_embd},resid_pdrop={resid_pdrop},scale_attn_weights={scale_attn_weights},summary_type={summary_type}"
+        )
+        self.assertEqual(n_embd, c.n_embd, "mismatch for key: n_embd")
+        self.assertEqual(resid_pdrop, c.resid_pdrop, "mismatch for key: resid_pdrop")
+        self.assertEqual(scale_attn_weights, c.scale_attn_weights, "mismatch for key: scale_attn_weights")
+        self.assertEqual(summary_type, c.summary_type, "mismatch for key: summary_type")