fix example - masking

examples/run_gpt2_interactive_conditional_samples.py → examples/run_gpt2.py

@@ -22,7 +22,7 @@ def top_k_logits(logits, k):
     min_values = values[:, -1]
     return torch.where(logits < min_values, torch.ones_like(logits, dtype=logits.dtype) * -1e10, logits)
 
-def sample_sequence(model, length, start_token=None, batch_size=None, context=None, temperature=1, top_k=0, device='cuda'):
+def sample_sequence(model, length, start_token=None, batch_size=None, context=None, temperature=1, top_k=0, device='cuda', sample=True):
     if start_token is None:
         assert context is not None, 'Specify exactly one of start_token and context!'
         context = torch.tensor(context, device=device, dtype=torch.long).unsqueeze(0).repeat(batch_size, 1)
@@ -38,11 +38,14 @@ def sample_sequence(model, length, start_token=None, batch_size=None, context=No
             logits = logits[:, -1, :] / temperature
             logits = top_k_logits(logits, k=top_k)
             log_probs = F.softmax(logits, dim=-1)
+            if sample:
                 prev = torch.multinomial(log_probs, num_samples=1)
+            else:
+                _, prev = torch.topk(log_probs, k=1, dim=-1)
             output = torch.cat((output, prev), dim=1)
     return output
 
-def interact_model():
+def run_model():
     parser = argparse.ArgumentParser()
     parser.add_argument('--model_name_or_path', type=str, default='gpt2', help='pretrained model name or path to local checkpoint')
     parser.add_argument("--seed", type=int, default=0)
@@ -51,6 +54,7 @@ def interact_model():
     parser.add_argument("--length", type=int, default=-1)
     parser.add_argument("--temperature", type=int, default=1)
     parser.add_argument("--top_k", type=int, default=0)
+    parser.add_argument('--unconditional', action='store_true', help='If true, unconditional generation.')
     args = parser.parse_args()
     print(args)
 
@@ -73,7 +77,8 @@ def interact_model():
     elif args.length > model.config.n_ctx:
         raise ValueError("Can't get samples longer than window size: %s" % model.config.n_ctx)
 
-    while True:
+    while not args.unconditional:
+        if not args.unconditional:
             raw_text = input("Model prompt >>> ")
             while not raw_text:
                 print('Prompt should not be empty!')
@@ -83,7 +88,8 @@ def interact_model():
         for _ in range(args.nsamples // args.batch_size):
             out = sample_sequence(
                 model=model, length=args.length,
-                context=context_tokens,
+                context=context_tokens if not args.unconditional else None,
+                start_token=enc.encoder['<|endoftext|>'] if args.unconditional else None,
                 batch_size=args.batch_size,
                 temperature=args.temperature, top_k=args.top_k, device=device
             )
@@ -96,5 +102,4 @@ def interact_model():
         print("=" * 80)
 
 if __name__ == '__main__':
-    interact_model()
-
+    run_model()

pytorch_pretrained_bert/modeling_gpt2.py

@@ -87,10 +87,6 @@ def load_tf_weights_in_gpt2(model, gpt2_checkpoint_path):
             if len(l) >= 2:
                 num = int(l[1])
                 pointer = pointer[num]
-        if m_name[-11:] == '_embeddings':
-            pointer = getattr(pointer, 'weight')
-        elif m_name == 'kernel':
-            array = np.transpose(array)
         try:
             assert pointer.shape == array.shape
         except AssertionError as e:
@@ -216,10 +212,9 @@ class Attention(nn.Module):
         w = torch.matmul(q, k)
         if self.scale:
             w = w / math.sqrt(v.size(-1))
-        # w = w * self.bias + -1e9 * (1 - self.bias)  # TF implem method: mask_attn_weights
-        # XD: self.b may be larger than w, so we need to crop it
-        b = self.bias[:, :, : w.size(-2), : w.size(-1)]
-        w = w * b + -1e10 * (1 - b)
+        nd, ns = w.size(-2), w.size(-1)
+        b = self.bias[:, :, ns-nd:ns, :ns]
+        w = w * b - 1e10 * (1 - b)
 
         w = nn.Softmax(dim=-1)(w)
         return torch.matmul(w, v)
@@ -233,9 +228,9 @@ class Attention(nn.Module):
         new_x_shape = x.size()[:-1] + (self.n_head, x.size(-1) // self.n_head)
         x = x.view(*new_x_shape)  # in Tensorflow implem: fct split_states
         if k:
-            return x.permute(0, 2, 3, 1)
+            return x.permute(0, 2, 3, 1)  # (batch, head, head_features, seq_length)
         else:
-            return x.permute(0, 2, 1, 3)
+            return x.permute(0, 2, 1, 3)  # (batch, head, seq_length, head_features)
 
     def forward(self, x, layer_past=None):
         x = self.c_attn(x)
@@ -244,10 +239,10 @@ class Attention(nn.Module):
         key = self.split_heads(key, k=True)
         value = self.split_heads(value)
         if layer_past is not None:
-            past_key, past_value = layer_past[0].transpose(-2, -1), layer_past[1]  # transpose to have same shapes
+            past_key, past_value = layer_past[0].transpose(-2, -1), layer_past[1]  # transpose back cf below
             key = torch.cat((past_key, key), dim=-1)
             value = torch.cat((past_value, value), dim=-2)
-        present = torch.stack((key.transpose(-2, -1), value))
+        present = torch.stack((key.transpose(-2, -1), value))  # transpose to have same shapes for stacking
         a = self._attn(query, key, value)
         a = self.merge_heads(a)
         a = self.c_proj(a)
@@ -522,7 +517,7 @@ class GPT2Model(GPT2PreTrainedModel):
         self.wpe = nn.Embedding(config.n_positions, config.n_embd)
         block = Block(config.n_ctx, config, scale=True)
         self.h = nn.ModuleList([copy.deepcopy(block) for _ in range(config.n_layer)])
-        self.ln_f = LayerNorm(config.n_embd)
+        self.ln_f = LayerNorm(config.n_embd, eps=config.layer_norm_epsilon)
 
         self.apply(self.init_weights)