mobilenet train speed is slow than full convolution?

[qingzhouzhen]

Is there something wrong with your symbol_mobilenet.py in line 22?
I fixed it in my repository in https://github.com/qingzhouzhen/mobilenet-mxnet,
And I both trained mobilenet with https://github.com/qingzhouzhen/mobilenet-mxnet/blob/master/mobilenet.py and https://github.com/qingzhouzhen/mobilenet-mxnet/blob/master/mobilenet_normal.py
Unfortunately, mobilenet is slower, mobilenet is about 50 samples/second, normal convolution is about 98 sample/second, why?

mobilenet tarin speed:
INFO:root:Epoch[0] Batch [20] Speed: 56.48 samples/sec accuracy=0.000744
INFO:root:Epoch[0] Batch [40] Speed: 56.53 samples/sec accuracy=0.000781
INFO:root:Epoch[0] Batch [60] Speed: 56.53 samples/sec accuracy=0.000000
INFO:root:Epoch[0] Batch [80] Speed: 56.55 samples/sec accuracy=0.001563
INFO:root:Epoch[0] Batch [100] Speed: 56.55 samples/sec accuracy=0.002344
INFO:root:Epoch[0] Batch [120] Speed: 56.55 samples/sec accuracy=0.002734
INFO:root:Epoch[0] Batch [140] Speed: 56.53 samples/sec accuracy=0.001563
INFO:root:Epoch[0] Batch [160] Speed: 56.53 samples/sec accuracy=0.002734
INFO:root:Epoch[0] Batch [180] Speed: 56.54 samples/sec accuracy=0.001172
INFO:root:Epoch[0] Batch [200] Speed: 56.50 samples/sec accuracy=0.002734
INFO:root:Epoch[0] Batch [220] Speed: 56.53 samples/sec accuracy=0.001953
INFO:root:Epoch[0] Batch [240] Speed: 56.55 samples/sec accuracy=0.003516
INFO:root:Epoch[0] Batch [260] Speed: 56.54 samples/sec accuracy=0.001953
INFO:root:Epoch[0] Batch [280] Speed: 56.55 samples/sec accuracy=0.005078
INFO:root:Epoch[0] Batch [300] Speed: 56.54 samples/sec accuracy=0.004297

the counterpart is:
INFO:root:Epoch[0] Batch [20] Speed: 92.89 samples/sec accuracy=0.002604
INFO:root:Epoch[0] Batch [40] Speed: 93.21 samples/sec accuracy=0.002344
INFO:root:Epoch[0] Batch [60] Speed: 93.19 samples/sec accuracy=0.003516
INFO:root:Epoch[0] Batch [80] Speed: 93.09 samples/sec accuracy=0.000781
INFO:root:Epoch[0] Batch [100] Speed: 93.11 samples/sec accuracy=0.001953
INFO:root:Epoch[0] Batch [120] Speed: 93.16 samples/sec accuracy=0.002344
INFO:root:Epoch[0] Batch [140] Speed: 93.16 samples/sec accuracy=0.001563
INFO:root:Epoch[0] Batch [160] Speed: 93.20 samples/sec accuracy=0.003906
INFO:root:Epoch[0] Batch [180] Speed: 93.35 samples/sec accuracy=0.003125
INFO:root:Epoch[0] Batch [200] Speed: 93.74 samples/sec accuracy=0.001953
INFO:root:Epoch[0] Batch [220] Speed: 93.65 samples/sec accuracy=0.002344
INFO:root:Epoch[0] Batch [240] Speed: 93.72 samples/sec accuracy=0.002344
INFO:root:Epoch[0] Batch [260] Speed: 93.62 samples/sec accuracy=0.002734
INFO:root:Epoch[0] Batch [280] Speed: 93.59 samples/sec accuracy=0.003125
INFO:root:Epoch[0] Batch [300] Speed: 93.51 samples/sec accuracy=0.002344
INFO:root:Epoch[0] Batch [320] Speed: 93.52 samples/sec accuracy=0.002344
INFO:root:Epoch[0] Batch [340] Speed: 93.59 samples/sec accuracy=0.003906
INFO:root:Epoch[0] Batch [360] Speed: 93.72 samples/sec accuracy=0.001953
INFO:root:Epoch[0] Batch [380] Speed: 93.47 samples/sec accuracy=0.002344
INFO:root:Epoch[0] Batch [400] Speed: 93.45 samples/sec accuracy=0.003516
INFO:root:Epoch[0] Batch [420] Speed: 93.59 samples/sec accuracy=0.002344
INFO:root:Epoch[0] Batch [440] Speed: 93.65 samples/sec accuracy=0.004297
INFO:root:Epoch[0] Batch [460] Speed: 93.70 samples/sec accuracy=0.004687
INFO:root:Epoch[0] Batch [480] Speed: 93.59 samples/sec accuracy=0.005859
INFO:root:Epoch[0] Batch [500] Speed: 93.73 samples/sec accuracy=0.006250

why mobilenet is slow than full convolution?

[wranglerwong]

@qingzhouzhen
because depthwise convolution implemented by group (group > 1) is much slower than normal convolution (group = 1)

See https://github.com/dmlc/mxnet/blob/master/src/operator/convolution-inl.h#L144