Hi all,

So I am trying to implement NllLoss function and completely lost within dimensions. Here is my attempt. Could someone please tell me what am I missing?

```
import torch
import torch.nn as nn
import torch.nn.functional as F
log_softmax = nn.LogSoftmax(dim=1)
torch.random.manual_seed(100)
logits = torch.randn([4, 2, 3, 1])
torch.random.manual_seed(200)
target = torch.randint_like(logits[:,1,:], 0, 2)
logp = log_softmax(logits)
logp1 = logits - torch.log(logits.exp().sum(1).unsqueeze(1)) #Log Softmax
print('Pytorch NllLoss:', F.nll_loss(logp, target.long()), F.nll_loss(logp1, target.long()))
loss1 = target * logp[:,0,:,:]
loss2 = (1.0 - target) * (1.0 - logp[:,1,:,:])
loss = loss1 + loss2
print('My Loss',torch.mean(loss))
```

Output:

Pytorch NllLoss: tensor(0.7951) tensor(0.7951)

My Loss tensor(0.7221)

Thanks!