Implement GPT2 greedy_until

lm_eval/base.py

@@ -38,9 +38,9 @@ class LM(abc.ABC):
             A list of pairs (context, until)
             context: str
                 Context string
-            until: str
-                The string sequence to generate until. This string sequence may 
-                span across multiple tokens, or may be part of one token.
+            until: [str]
+                The string sequences to generate until. These string sequences 
+                may each span across multiple tokens, or may be part of one token.
         :return: list
             A list of strings continuation
             continuation: str

lm_eval/models/gpt2.py

@@ -7,6 +7,8 @@ from tqdm import tqdm
 
 
 class GPT2LM(LM):
+    MAX_GEN_TOKS = 256
+
     def __init__(self, device="cpu", pretrained='gpt2'):
         self.device = torch.device(device)
         self.gpt2 = transformers.GPT2LMHeadModel.from_pretrained(pretrained).to(self.device)
@@ -23,6 +25,7 @@ class GPT2LM(LM):
         res = []
         with torch.no_grad():
             # TODO: vectorize properly
+            # TODO: automatic batch size detection for vectorization
             for context, continuation in tqdm(requests):
                 # when too long to fit in context, truncate from the left
 
@@ -50,5 +53,29 @@ class GPT2LM(LM):
         return res
     
     def greedy_until(self, requests):
-        # TODO: implement
-        pass
+        # TODO: implement fully general `until` that handles untils that are 
+        # multiple tokens or that span multiple tokens correctly
+        res = []
+
+        for context, until in tqdm(requests):
+            if isinstance(until, str): until = [until]
+
+            context_enc = torch.tensor([self.tokenizer.encode(context)]).to(self.device)
+
+            primary_until, = self.tokenizer.encode(until[0])
+
+            cont = self.gpt2.generate(
+                context_enc,
+                max_length=self.MAX_GEN_TOKS,
+                eos_token_id=primary_until,
+                do_sample=False
+            )
+
+            s = self.tokenizer.decode(cont[0].tolist()[context_enc.shape[1]:])
+
+            for term in until:
+                s = s.split(term)[0]
+            
+            res.append(s)
+        
+        return res

lm_eval/models/gpt3.py

@@ -113,6 +113,7 @@ class GPT3LM(LM):
                 max_tokens=self.MAX_GEN_TOKS, 
                 temperature=0.,
                 logprobs=10,
+                stop=until
             )
 
             res.append(response.choices[0]['text'])

tests/test_models.py

@@ -12,4 +12,10 @@ def test_gpt2():
     assert not ig_cat
 
     # test empty context
-    gpt2.loglikelihood([('', 'test')])
+    gpt2.loglikelihood([('', 'test')])
\ No newline at end of file
+
+    gen, = gpt2.greedy_until([
+        ('The quick brown fox jumps over the lazy', ['.', '\n'])
+    ])
+
+    assert gen == ', lazy fox and they both fall to the ground'
\ No newline at end of file