Hello @ptrblck thank you for fast response. I have see the documentation again and again and finally I am choosing size NCW and target NW so it will be like (64,3,640) and target (64,640) as state in here 15 which using log softmax followed by NLLLoss. However I got this kind of error:
RuntimeError: Assertioncur_target >= 0 && cur_target < n_classes’ failed. at /opt/conda/conda-bld/pytorch-nightly_1538995270066/work/aten/src/THNN/generic/SpatialClassNLLCriterion.c:110`
And finally I realize because the groundtruth value must normalize since probability is from 0 to 1 . Thank you so much for your help.