update alibi

csrc/attention/attention_kernels_opt_tc.cu

@@ -281,7 +281,7 @@ __device__ void paged_attention_kernel_TC(
         const int token_idx = block_idx * BLOCK_SIZE+rowid;
         if(alibi_slope[i] != 0){
           float alibi=alibi_slope[i]* (token_idx - seq_len + 1);
-          qk_vec[i] = alibi;
+          qk_vec[i] += alibi;
         }
 
         const bool mask = (token_idx >= seq_len);