Memory leakage in long term forecast

[MyssH]

Description: I encountered a memory leakage issue when using a large dataset for long-term forecasting. It seems the problem occurred because the loss was being accumulated as a tensor instead of a scalar.

Solution: To fix this, I changed: loss_val += loss to loss_val += loss.item() at the following lines:

• exp/exp_long_term_forecasting.py#144

• exp/exp_long_term_forecasting.py#149

[WenWeiTHU]

Thanks for your feedback! We'll fix it :)