Efficient implementation of SSIM

[ragavvenkatesan]

Is there any particular reason for storing the preds and target in SSIM and MSSSIM in here, instead of storing computed and total? We could just compute the averages in compute method and calculate the actual SSIM and MSSSIM on a mini-batch basis on the update method and keep track. The reason why we might want this is because in its current form, SSIM and MSSSIM cannot be tracked during say validation or in any cases, where we do not want to reset them at in the _step_end methods and instead reset them in the _epoch_end methods.

Thanks, R

[SkafteNicki]

Hi @ragavvenkatesan,
I do not think that there is any particular reason that preds and target is stored. Would you be willing sending a PR fixing this?

[ragavvenkatesan]

I could. Sorry I was out for a while. I can try and help fixing this.