High validation loss, high validation accuracy

Question

I'm just getting started into the field of deep learning, and I completed my first model training using PyTorch.

I decided to use a pre-build model from torchvision, more specifically the mobilenet_v2 (https://pytorch.org/docs/stable/_modules/torchvision/models/mobilenet.html#mobilenet_v2) on a custom dataset for binary classification.

I manage to get 100% accuracy for both training and test sets (this particular dataset is not a difficult one, so nothing weird about that)

What I don't understand is why the test loss seems to be several orders of magnitude higher than the train loss, while the accuracy is 100% in both cases. Could someone here explain me what is happening here?

I show you the training stats below:

Epoch: 1/15, Train Loss: 0.22990, Train accuracy: 88.48%, Test Loss: 2.10275, Test accuracy: 99.22%

Epoch: 2/15, Train Loss: 0.03988, Train accuracy: 99.41%, Test Loss: 2.08563, Test accuracy: 99.22%

Epoch: 3/15, Train Loss: 0.02211, Train accuracy: 99.41%, Test Loss: 2.05521, Test accuracy: 100.00%

Epoch: 4/15, Train Loss: 0.01173, Train accuracy: 99.80%, Test Loss: 2.05332, Test accuracy: 100.00%

Epoch: 5/15, Train Loss: 0.00499, Train accuracy: 100.00%, Test Loss: 2.04989, Test accuracy: 100.00%

Epoch: 6/15, Train Loss: 0.00381, Train accuracy: 100.00%, Test Loss: 2.04952, Test accuracy: 100.00%

Epoch: 7/15, Train Loss: 0.00171, Train accuracy: 100.00%, Test Loss: 2.04999, Test accuracy: 100.00%

Epoch: 8/15, Train Loss: 0.00072, Train accuracy: 100.00%, Test Loss: 2.04971, Test accuracy: 100.00%

Epoch: 9/15, Train Loss: 0.00045, Train accuracy: 100.00%, Test Loss: 2.04938, Test accuracy: 100.00%

Epoch: 10/15, Train Loss: 0.00035, Train accuracy: 100.00%, Test Loss: 2.04932, Test accuracy: 100.00%

Epoch: 11/15, Train Loss: 0.00029, Train accuracy: 100.00%, Test Loss: 2.04920, Test accuracy: 100.00%

Epoch: 12/15, Train Loss: 0.00025, Train accuracy: 100.00%, Test Loss: 2.04922, Test accuracy: 100.00%

Epoch: 13/15, Train Loss: 0.00022, Train accuracy: 100.00%, Test Loss: 2.04906, Test accuracy: 100.00%

Epoch: 14/15, Train Loss: 0.00020, Train accuracy: 100.00%, Test Loss: 2.04914, Test accuracy: 100.00%

Epoch: 15/15, Train Loss: 0.00018, Train accuracy: 100.00%, Test Loss: 2.04905, Test accuracy: 100.00%

Answer 1

In binary classification we have either 0 or 1. You must be using softmax function at the end layer to get the output . It ranges from (0,1)
Loss: Generally speaking , it is the difference between predicted and actual value.
Suppose
CASE 1:predicted value is 0.6 real answer is 1.
CASE 2:predicted value is 0.9 real answer is 1.
Although they both have the correct answers(because they both round off to become 1) , loss in case 2 is less than case 1.