Switch to torch SDPA

awq/modules/fused/attn.py

@@ -154,6 +154,28 @@ class QuantAttentionFused(nn.Module):
             self.alibi_slopes = None
             self.is_neox = True
     
+    def _multi_query_attention_torch(self, query, key, value, batch_size, seqlen, use_cache, past_key_value, attention_mask):
+        query = query.view(batch_size, seqlen, self.n_local_heads, self.head_dim).transpose(1, 2)
+        key = key.view(batch_size, seqlen, self.n_local_heads, self.head_dim).transpose(1, 2)
+        value = value.view(batch_size, seqlen, self.n_local_heads, self.head_dim).transpose(1, 2)
+
+        if use_cache:
+            key = key.contiguous()
+            value = value.contiguous()
+            query = query.contiguous()
+
+        output = F.scaled_dot_product_attention(
+            query, key, value, 
+            is_causal=past_key_value is None, 
+            attn_mask=attention_mask)
+        
+
+        del query, key, value
+
+        output = output.transpose(1, 2).reshape(batch_size, seqlen, self.hidden_size)
+
+        return output
+    
     def forward(
         self,
         hidden_states, past_key_value=None, attention_mask=None, position_ids=None, output_attentions=False, use_cache=False
@@ -186,24 +208,12 @@ class QuantAttentionFused(nn.Module):
             self.cache_v[:bsz, :, self.start_pos : self.start_pos + seqlen, :] = values_store
             self.cache_k[:bsz, :, :, self.start_pos : self.start_pos + seqlen, :] = keys_store
 
-            keys = xk
-            values = xv
             past_key_value = (xk, xv) if use_cache else None
-
-            xq = xq.transpose(1, 2)
-            keys = keys.transpose(1, 2)
-            values = values.transpose(1, 2)
-            scores = torch.matmul(xq, keys.transpose(2, 3)) / math.sqrt(self.head_dim)
-            
-            if self.use_alibi:
-                scores += self.alibi_bias[..., :seqlen]
-
-            if attention_mask is not None:
-                scores = scores + attention_mask  # (bs, n_local_heads, slen, cache_len + slen)
-            
-            scores = F.softmax(scores.float(), dim=-1).type_as(xq)
-            output = torch.matmul(scores, values)  # (bs, n_local_heads, slen, head_dim)
-            output = output.transpose(1, 2).contiguous().view(bsz, seqlen, -1)
+            output = self._multi_query_attention_torch(
+                xq, xk, xv, 
+                bsz, seqlen, True, 
+                past_key_value, attention_mask
+            )
         else:
             xq = xq[:, 0, :, :]
             xk = xk[:, 0, :, :]
@@ -231,4 +241,4 @@ class QuantAttentionFused(nn.Module):
         else:
             self.start_pos = 0
 
-        return attn_output, None, past_key_value
+        return attn_output, None, past_key_value
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