Very slow at the last epoch

[Willirene]

Excuse me, when I run this command:
python LightGCN.py --dataset gowalla --regs [1e-4] --embed_size 64 --layer_size [64,64,64] --lr 0.001 --batch_size 2048 --epoch 20
I got the following result:

My problem is that why the final epoch cost so much time than previous epoch?
(13s to 350s)

[kuandeng]

Every 20 epochs, the program will evaluate the precision on the test data set, which will take a lot of time.