Blocks deletion from already deleted heads. Necessary integration test.

Now raises a warning when a head to be deleted already has been deleted. An integration test verifying the total pipeline (-> from config -> save model -> load model -> additional head pruning) has been added.

pytorch_transformers/modeling_bert.py

@@ -651,6 +651,7 @@ class BertModel(BertPreTrainedModel):
 
         if hasattr(config, "pruned_heads"):
             pruned_heads = config.pruned_heads.copy().items()
+            config.pruned_heads = {}
             for layer, heads in pruned_heads:
                 if self.encoder.layer[int(layer)].attention.self.num_attention_heads == config.num_attention_heads:
                     self.prune_heads({int(layer): list(map(int, heads))})

pytorch_transformers/modeling_gpt2.py

@@ -455,6 +455,7 @@ class GPT2Model(GPT2PreTrainedModel):
 
         if hasattr(config, "pruned_heads"):
             pruned_heads = config.pruned_heads.copy().items()
+            config.pruned_heads = {}
             for layer, heads in pruned_heads:
                 if self.h[int(layer)].attn.n_head == config.n_head:
                     self.prune_heads({int(layer): list(map(int, heads))})

pytorch_transformers/modeling_openai.py

@@ -458,6 +458,7 @@ class OpenAIGPTModel(OpenAIGPTPreTrainedModel):
 
         if hasattr(config, "pruned_heads"):
             pruned_heads = config.pruned_heads.copy().items()
+            config.pruned_heads = {}
             for layer, heads in pruned_heads:
                 if self.h[int(layer)].attn.n_head == config.n_head:
                     self.prune_heads({int(layer): list(map(int, heads))})

pytorch_transformers/modeling_utils.py

@@ -201,6 +201,10 @@ class PretrainedConfig(object):
         # Load config
         config = cls.from_json_file(resolved_config_file)
 
+        if hasattr(config, 'pruned_heads'):
+            config.pruned_heads = {int(key): value for key, value in config.pruned_heads.items()}
+
+
         # Update config with kwargs if needed
         to_remove = []
         for key, value in kwargs.items():
@@ -365,15 +369,22 @@ class PreTrainedModel(nn.Module):
         """
         base_model = getattr(self, self.base_model_prefix, self)  # get the base model if needed
 
+        to_be_pruned = {}
+
         for layer, heads in heads_to_prune.items():
-            if str(layer) not in self.config.pruned_heads:
-                self.config.pruned_heads[str(layer)] = heads
+            if int(layer) not in self.config.pruned_heads:
+                self.config.pruned_heads[int(layer)] = heads
+                to_be_pruned[int(layer)] = heads
             else:
                 for head in heads:
-                    if head not in self.config.pruned_heads[str(layer)]:
-                        self.config.pruned_heads[str(layer)].append(head)
+                    if head not in self.config.pruned_heads[int(layer)]:
+                        self.config.pruned_heads[int(layer)].append(head)
+                        to_be_pruned[int(layer)].append(head)
+                    else:
+                        logger.warning(f"Tried to remove head {head} of layer {layer} but it was already removed. "
+                                       f"The removed heads are {heads_to_prune}")
 
-        base_model._prune_heads(heads_to_prune)
+        base_model._prune_heads(to_be_pruned)
 
     def save_pretrained(self, save_directory):
         """ Save a model and its configuration file to a directory, so that it

pytorch_transformers/modeling_xlm.py

@@ -561,6 +561,7 @@ class XLMModel(XLMPreTrainedModel):
 
         if hasattr(config, "pruned_heads"):
             pruned_heads = config.pruned_heads.copy().items()
+            config.pruned_heads = {}
             for layer, heads in pruned_heads:
                 if self.attentions[int(layer)].n_heads == config.n_heads:
                     self.prune_heads({int(layer): list(map(int, heads))})

pytorch_transformers/tests/modeling_common_test.py

@@ -262,12 +262,9 @@ class CommonTestCases:
 
                 outputs = model(**inputs_dict)
                 attentions = outputs[-1]
-                self.assertEqual(
-                    attentions[0].shape[-3], 1)
-                self.assertEqual(
-                    attentions[1].shape[-3], self.model_tester.num_attention_heads)
-                self.assertEqual(
-                    attentions[-1].shape[-3], self.model_tester.num_attention_heads - 1)
+                self.assertEqual(attentions[0].shape[-3], 1)
+                self.assertEqual(attentions[1].shape[-3], self.model_tester.num_attention_heads)
+                self.assertEqual(attentions[-1].shape[-3], self.model_tester.num_attention_heads - 1)
 
                 shutil.rmtree(directory)
 
@@ -293,12 +290,67 @@ class CommonTestCases:
 
                 outputs = model(**inputs_dict)
                 attentions = outputs[-1]
-                self.assertEqual(
-                    attentions[0].shape[-3], 1)
-                self.assertEqual(
-                    attentions[1].shape[-3], self.model_tester.num_attention_heads)
-                self.assertEqual(
-                    attentions[-1].shape[-3], self.model_tester.num_attention_heads - 1)
+
+                self.assertEqual(attentions[0].shape[-3], 1)
+                self.assertEqual(attentions[1].shape[-3], self.model_tester.num_attention_heads)
+                self.assertEqual(attentions[-1].shape[-3], self.model_tester.num_attention_heads - 1)
+
+        def test_head_pruning_integration(self):
+            if not self.test_pruning:
+                return
+
+            for model_class in self.all_model_classes:
+                config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
+
+                if "head_mask" in inputs_dict:
+                    del inputs_dict["head_mask"]
+
+                config.output_attentions = True
+                config.output_hidden_states = False
+
+                heads_to_prune = {0: [0], 1: [1, 2]}
+                config.pruned_heads = heads_to_prune
+
+                model = model_class(config=config)
+                model.eval()
+
+                outputs = model(**inputs_dict)
+                attentions = outputs[-1]
+
+                self.assertEqual(attentions[0].shape[-3], self.model_tester.num_attention_heads - 1)
+                self.assertEqual(attentions[1].shape[-3], self.model_tester.num_attention_heads - 2)
+                self.assertEqual(attentions[2].shape[-3], self.model_tester.num_attention_heads)
+                self.assertEqual(attentions[3].shape[-3], self.model_tester.num_attention_heads)
+
+                directory = "pruned_model"
+
+                if not os.path.exists(directory):
+                    os.makedirs(directory)
+                model.save_pretrained(directory)
+                model = model_class.from_pretrained(directory)
+                shutil.rmtree(directory)
+
+                outputs = model(**inputs_dict)
+                attentions = outputs[-1]
+
+                self.assertEqual(attentions[0].shape[-3], self.model_tester.num_attention_heads - 1)
+                self.assertEqual(attentions[1].shape[-3], self.model_tester.num_attention_heads - 2)
+                self.assertEqual(attentions[2].shape[-3], self.model_tester.num_attention_heads)
+                self.assertEqual(attentions[3].shape[-3], self.model_tester.num_attention_heads)
+
+                heads_to_prune = {0: [0], 2: [1, 2]}
+                model.prune_heads(heads_to_prune)
+
+                outputs = model(**inputs_dict)
+                attentions = outputs[-1]
+
+                self.assertEqual(attentions[0].shape[-3], self.model_tester.num_attention_heads -1)
+                self.assertEqual(attentions[1].shape[-3], self.model_tester.num_attention_heads - 2)
+                self.assertEqual(attentions[2].shape[-3], self.model_tester.num_attention_heads - 2)
+                self.assertEqual(attentions[3].shape[-3], self.model_tester.num_attention_heads)
+
+                self.assertDictEqual(model.config.pruned_heads, {0: [0], 1: [1, 2], 2: [1, 2]})
+
 
         def test_hidden_states_output(self):
             config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()