gluoncv 训练速度慢慢变慢


#1
poch[0] Batch [199]    Speed: 5069.164103 samples/sec  rmse=0.026370   lr=0.012792
poch[0] Batch [249]    Speed: 5043.046216 samples/sec  rmse=0.026357   lr=0.015990
poch[0] Batch [299]    Speed: 4974.609027 samples/sec  rmse=0.026421   lr=0.019188
poch[0] Batch [349]    Speed: 5019.370472 samples/sec  rmse=0.026435   lr=0.022386
poch[0] Batch [399]    Speed: 4978.102321 samples/sec  rmse=0.026300   lr=0.025584
poch[0] Batch [449]    Speed: 4836.921195 samples/sec  rmse=0.026334   lr=0.028782
poch[0] Batch [499]    Speed: 4817.141158 samples/sec  rmse=0.026299   lr=0.031980
poch[0] Batch [549]    Speed: 4774.665527 samples/sec  rmse=0.026318   lr=0.035177
poch[0] Batch [599]    Speed: 4796.575619 samples/sec  rmse=0.026293   lr=0.038375
poch[0] Batch [649]    Speed: 4792.456164 samples/sec  rmse=0.026319   lr=0.041573
poch[0] Batch [699]    Speed: 4776.245693 samples/sec  rmse=0.026324   lr=0.044771
poch[0] Batch [749]    Speed: 4798.449612 samples/sec  rmse=0.026309   lr=0.047969
poch[0] Batch [799]    Speed: 4782.119303 samples/sec  rmse=0.026338   lr=0.051167
poch[0] Batch [849]    Speed: 4767.269982 samples/sec  rmse=0.026294   lr=0.054365
poch[0] Batch [899]    Speed: 4777.752497 samples/sec  rmse=0.026250   lr=0.057563
poch[0] Batch [949]    Speed: 4763.056904 samples/sec  rmse=0.026246   lr=0.060761

...............


Epoch[1] Batch [99]     Speed: 4788.660366 samples/sec  rmse=0.025799   lr=0.086473
Epoch[1] Batch [149]    Speed: 4759.630192 samples/sec  rmse=0.026007   lr=0.089671
Epoch[1] Batch [199]    Speed: 4773.491487 samples/sec  rmse=0.026060   lr=0.092869
Epoch[1] Batch [249]    Speed: 4785.585737 samples/sec  rmse=0.025986   lr=0.096067
Epoch[1] Batch [299]    Speed: 4765.650166 samples/sec  rmse=0.025863   lr=0.099264

log如上面所示,训练的Mobilenet1.0 , 为什么速度会降下来呢?

谢谢!