when training st-gcn the loss will turn into NAN

[ppppppi1]

[02.06.24|21:04:38] Training epoch: 0
[02.06.24|21:13:26] Iter 0 Done. | loss: 1.4058 | lr: 0.010000
[02.06.24|21:13:31] mean_loss: nan
[02.06.24|21:13:31] Time consumption:
[02.06.24|21:13:31] Done.
[02.06.24|21:13:31] Training epoch: 1
[02.06.24|21:13:40] mean_loss: nan
[02.06.24|21:13:40] Time consumption:
[02.06.24|21:13:40] Done.
[02.06.24|21:13:40] The model has been saved as D:/dataset/2024.2.6_result2/epoch2_model.pt.
[02.06.24|21:13:40] Eval epoch: 1
[02.06.24|21:13:47] mean_loss: nan
[02.06.24|21:13:47] Top1: 25.00%
[02.06.24|21:13:47] Top5: 100.00%
[02.06.24|21:13:47] Done.
[02.06.24|21:13:47] Training epoch: 2
[02.06.24|21:13:56] mean_loss: nan
[02.06.24|21:13:56] Time consumption:
[02.06.24|21:13:56] Done.
[02.06.24|21:13:56] Training epoch: 3
[02.06.24|21:14:05] mean_loss: nan
[02.06.24|21:14:05] Time consumption:
[02.06.24|21:14:05] Done.
[02.06.24|21:14:05] The model has been saved as D:/dataset/2024.2.6_result2/epoch4_model.pt.
[02.06.24|21:14:05] Eval epoch: 3
[02.06.24|21:14:11] mean_loss: nan
[02.06.24|21:14:11] Top1: 25.00%
[02.06.24|21:14:11] Top5: 100.00%
[02.06.24|21:14:11] Done.
[02.06.24|21:14:11] Training epoch: 4

[ppppppi1]

why and how