Small eigenvalues can lead to failure when computing cholesky decompsotion on
gpu. To prevent that, explicitly ensure that eigenvalues are not too small.

Matrix ops optimization group is created. Magma by default take precedence
during optimization. If magma is not available, cusolver cholesky decomposition
is used.

Repack the pickle with protocol 2 and open in binary mode.

Implementing `GpuAdvancedIncSubtensor`

Correct a typo in make_node function (tensore.nnet.SoftmaxWithBias)

Remove output guard