In C++ API 1.0.0, MNIST results are unstable

C++
#1

I’m running mnist example as same as python but it seems to be unstable.

  • manual_seed might not work well
  • after several epochs, loss and accuracy got wrong
  • both CPU and GPU have this problem
  • I’m using libtorch installed with conda install pytorch=1.0.0 -c pytorch 
▶ ./mnist | grep Accuracy
Test set: Average loss: 0.098864, Accuracy: 0.9693
Test set: Average loss: 0.0540888, Accuracy: 0.9813
Test set: Average loss: 0.0359754, Accuracy: 0.9883
Test set: Average loss: 0.0464136, Accuracy: 0.9844
Test set: Average loss: nan, Accuracy: 0.098
Test set: Average loss: nan, Accuracy: 0.098
Test set: Average loss: nan, Accuracy: 0.098
Test set: Average loss: nan, Accuracy: 0.098
Test set: Average loss: nan, Accuracy: 0.098

▶ ./mnist | grep Accuracy
Test set: Average loss: 0.0982789, Accuracy: 0.9702
Test set: Average loss: 0.0553075, Accuracy: 0.9808
Test set: Average loss: 0.0357092, Accuracy: 0.9878
Test set: Average loss: 0.0512756, Accuracy: 0.9844
Test set: Average loss: 0.0566966, Accuracy: 0.9843
Test set: Average loss: nan, Accuracy: 0.098
Test set: Average loss: nan, Accuracy: 0.098
Test set: Average loss: nan, Accuracy: 0.098
Test set: Average loss: nan, Accuracy: 0.098
Test set: Average loss: nan, Accuracy: 0.098

▶ ./mnist | grep Accuracy
Test set: Average loss: 0.0987975, Accuracy: 0.9697
Test set: Average loss: 0.0572588, Accuracy: 0.9794
Test set: Average loss: 0.0364755, Accuracy: 0.9878
Test set: Average loss: 0.0520559, Accuracy: 0.983
Test set: Average loss: 2.30402, Accuracy: 0.1135
Test set: Average loss: 2.31102, Accuracy: 0.1135
Test set: Average loss: 2.33372, Accuracy: 0.1135
Test set: Average loss: 2.40776, Accuracy: 0.1135
Test set: Average loss: 2.6472, Accuracy: 0.1135
Test set: Average loss: 3.42565, Accuracy: 0.1135

you can see my code at

#2

I also tried latest build on CPU and CUDA9.

https://download.pytorch.org/libtorch/cu90/libtorch-shared-with-deps-latest.zip

They still have the accuracy issue but the manual seed problem seems to be fixed on CPU and GPU respectively. Unfortunately the latest build seems to be much slower than 1.0.0 release 19 sec -> 87 sec (maybe debug build?).

My makefile above can accept following options to use the latest unzipped libtorch.

make INCPATH="-I$HOME/Downloads/libtorch/include -I$HOME/Downloads/libtorch/include/torch/csrc/api/include"  LIBPATH=$HOME/Downloads/libtorch/lib

(You need to add NO_CUDA=True if you use no cuda binary)

#3

You need to set -DCMAKE_BUILD_TYPE=Relase to enable optimizations. Otherwise it’s the debug build.

I’m looking into the NaN issues.