Cost nan

[mahmoudaymo]

Bug description

When training a model with guided alignment the training cost is always nan.

How to reproduce

/marian/build/marian -c $exp_dir/config.yml
--valid-log $exp_dir/valid.log
--log $exp_dir/train.log
--model $exp_dir/model.npz
--after 10e
--guided-alignment exp_dir/corpus.align
--guided-alignment-cost ce

Context

• Marian version: 1.12.0
• CMake command: Type the cmake command you used and attach the output of --build-info all
• Log file: Attach your training/decoding logs
  marian.logs.txt

Add any other information about the problem here.