some questions about ssim function

[ghost]

Hello, no error was reported when I used the ssim function api to calculate the ssim value, but the calculated ssim value was negative. This is not normal, because the ssim value should be [0-1], but I don't know what is wrong, do you have any suggestions?

[snk4tr]

@xiaoyangx0 could you provide a minimal example of the code + data that results in negative values? We do not observe such behavior on data from general IQA datasets e.g., TID2013, KADID-10k and PIPAL.

[ghost]

shadow_ssim += ssim(original_data, shadow_inv_output_, reduction='sum').item() shadow_psnr += psnr(original_data, shadow_inv_output_, reduction='sum').item()
Thank you for your reply. My original intention was to generate a picture through a model and compare the similarity with the original picture. The code for using the ssim has been uploaded. However, no bug was displayed when I used the ssim. However, when I used tensorboard to display the ssim change curve, I found that some places were negative.
<img width="479" alt="image" src="https://user-images.githubusercontent.com/62381232/223094975-2b5f2603-6004-4f16-a5f6-3056c4d9170e.png">

[Moleculebo]

@xiaoyangx0 Do you have solved the problem? Could you clarify it? Thanks!