Seq2Seq support (including FLAN-T5) (#1535)

---------

Co-authored-by: oobabooga <112222186+oobabooga@users.noreply.github.com>

modules/models.py

@@ -11,7 +11,8 @@ import torch
 import transformers
 from accelerate import infer_auto_device_map, init_empty_weights
 from transformers import (AutoConfig, AutoModel, AutoModelForCausalLM,
-                          AutoTokenizer, BitsAndBytesConfig, LlamaTokenizer)
+                          AutoModelForSeq2SeqLM, AutoTokenizer,
+                          BitsAndBytesConfig, LlamaTokenizer)
 
 import modules.shared as shared
 from modules import llama_attn_hijack
@@ -55,7 +56,12 @@ def find_model_type(model_name):
     elif any((k in model_name for k in ['gpt4chan', 'gpt-4chan'])):
         return 'gpt4chan'
     else:
-        return 'HF_generic'
+        config = AutoConfig.from_pretrained(f"{shared.args.model_dir}/{model_name}")
+        # Not a "catch all", but fairly accurate
+        if config.to_dict().get("is_encoder_decoder", False):
+            return 'HF_seq2seq'
+        else:
+            return 'HF_generic'
 
 
 def load_model(model_name):
@@ -66,6 +72,9 @@ def load_model(model_name):
     if shared.model_type == 'chatglm':
         LoaderClass = AutoModel
         trust_remote_code = shared.args.trust_remote_code
+    elif shared.model_type == 'HF_seq2seq':
+        LoaderClass = AutoModelForSeq2SeqLM
+        trust_remote_code = False
     else:
         LoaderClass = AutoModelForCausalLM
         trust_remote_code = False

modules/text_generation.py

@@ -58,12 +58,21 @@ def encode(prompt, add_special_tokens=True, add_bos_token=True, truncation_lengt
 
 
 def decode(output_ids, skip_special_tokens=True):
-    if skip_special_tokens:
-        reply = shared.tokenizer.decode(output_ids, skip_special_tokens=True)
-        reply = reply.replace(r'<|endoftext|>', '')
-        return reply
+    return shared.tokenizer.decode(output_ids, skip_special_tokens)
+
+
+def get_reply_from_output_ids(output_ids, input_ids, original_question, state):
+    if shared.model_type == 'HF_seq2seq':
+        reply = decode(output_ids, state['skip_special_tokens'])
+        if not shared.is_chat():
+            reply = apply_extensions('output', reply)
     else:
-        return shared.tokenizer.decode(output_ids, skip_special_tokens=False)
+        new_tokens = len(output_ids) - len(input_ids[0])
+        reply = decode(output_ids[-new_tokens:], state['skip_special_tokens'])
+        if not shared.is_chat():
+            reply = original_question + apply_extensions('output', reply)
+
+    return reply
 
 
 def generate_softprompt_input_tensors(input_ids):
@@ -262,11 +271,7 @@ def generate_reply(question, state, eos_token=None, stopping_strings=[]):
             if shared.soft_prompt:
                 output = torch.cat((input_ids[0], output[filler_input_ids.shape[1]:]))
 
-            new_tokens = len(output) - len(input_ids[0])
-            reply = decode(output[-new_tokens:], state['skip_special_tokens'])
-            if not shared.is_chat():
-                reply = original_question + apply_extensions('output', reply)
-
+            reply = get_reply_from_output_ids(output, input_ids, original_question, state)
             yield formatted_outputs(reply, shared.model_name)
 
         # Stream the reply 1 token at a time.
@@ -282,7 +287,7 @@ def generate_reply(question, state, eos_token=None, stopping_strings=[]):
             def generate_with_streaming(**kwargs):
                 return Iteratorize(generate_with_callback, kwargs, callback=None)
 
-            if not shared.is_chat():
+            if not shared.is_chat() and shared.model_type != 'HF_seq2seq':
                 yield formatted_outputs(original_question, shared.model_name)
 
             with generate_with_streaming(**generate_params) as generator:
@@ -290,11 +295,7 @@ def generate_reply(question, state, eos_token=None, stopping_strings=[]):
                     if shared.soft_prompt:
                         output = torch.cat((input_ids[0], output[filler_input_ids.shape[1]:]))
 
-                    new_tokens = len(output) - len(input_ids[0])
-                    reply = decode(output[-new_tokens:], state['skip_special_tokens'])
-                    if not shared.is_chat():
-                        reply = original_question + apply_extensions('output', reply)
-
+                    reply = get_reply_from_output_ids(output, input_ids, original_question, state)
                     if output[-1] in eos_token_ids:
                         break
 
@@ -310,11 +311,7 @@ def generate_reply(question, state, eos_token=None, stopping_strings=[]):
                 if shared.soft_prompt:
                     output = torch.cat((input_ids[0], output[filler_input_ids.shape[1]:]))
 
-                new_tokens = len(output) - len(original_input_ids[0])
-                reply = decode(output[-new_tokens:], state['skip_special_tokens'])
-                if not shared.is_chat():
-                    reply = original_question + apply_extensions('output', reply)
-
+                reply = get_reply_from_output_ids(output, input_ids, original_question, state)
                 if np.count_nonzero(np.isin(input_ids[0], eos_token_ids)) < np.count_nonzero(np.isin(output, eos_token_ids)):
                     break
 
@@ -334,6 +331,6 @@ def generate_reply(question, state, eos_token=None, stopping_strings=[]):
     finally:
         t1 = time.time()
         original_tokens = len(original_input_ids[0])
-        new_tokens = len(output) - original_tokens
+        new_tokens = len(output) - (original_tokens if shared.model_type != 'HF_seq2seq' else 0)
         print(f'Output generated in {(t1-t0):.2f} seconds ({new_tokens/(t1-t0):.2f} tokens/s, {new_tokens} tokens, context {original_tokens}, seed {seed})')
         return