We used 双败淘汰赛 in 1964 school competition too, i.e. with 1 负 you still can continue with the game until final unless having 2 负. For 双败淘汰赛 with 8 players, we need 4 rounds or 5 rounds depending on the result of Round 4. 棋手 with 3 胜 cannot be given 冠军 yet as minimum number of rounds is 4, i.e. he still need to play one more round with the only player having 1 负, if he fails in Round 4, Round 5 is needed again for the same two players as both players having 1 负 now.