测试结果：
tanh前向 7x5 70x50 700x500 7000x5000
default 253.9 289.46 3545.26 317929.42
lsx 329.99 336.24 1441.16 117446.49
boost ratio -30.0% -16.2% 59.3% 63.1%
tanh反向 7x5 70x50 700x500 7000x5000
default 253.34 279.61 1439.92 160105.65
lsx 212.86 222.05 871.89 133979.51
boost ratio 16.0% 20.6% 39.4% 16.3%
