ImageDreamfusion accumulate grad, guidance_eval in sd,if

[voletiv]

1. Accumulates grad in imagedreamfusion Fixes imagedreamfusion to accumulate grads from ref and guidance

2. Adds guidance_eval to stable_diffusion, deep_floyd Adds the ability to optionally evaluate guidance periodically, in stable_diffusion and deep_floyd (as done in zero123)

This does not affect current working of stable_diffusion, deep_floyd, it only adds the option to visualize the guidance.

Example

I used the following command to check the results with stable diffusion guidance: python launch.py --config configs/experimental/imagecondition.yaml --train --gpu 0 system.freq.ref_only_steps=20 system.freq.guidance_eval=13

To run with deep floyd guidance, I uncommented the requisite lines in configs/experimental/imagecondition.yaml.

First, since ref_only_steps=20, it should run with just rgb_loss for 20 iterations. Then, from 21st iteration, it should also compute guidance loss. Then, since freq.guidance_eval=13, at the 26th iteration, it should save the results of guidance_eval:

With stable-diffusion:

With deep-floyd:

[claforte]

@bennyguo this introduces redundancies but I think it's a good short-term step... so unless you have a concern, we'd like to merge it today. Later I recommend we fold some of the loss calculation/logging code in the base system class and maybe fold some of the eval guidance logic in the base guidance class, to avoid unnecessary code duplication. How does that sound?

[voletiv]

I've folded guidance_eval_save into base.py, and address the comments. Please check!

[voletiv]

Tested! Merging with main