Classifier-Free Guidance Formulation

[MoayedHajiAli]

In the classifier-free guidance paper, the formulation is as follow

However, it is implemented in DALL-2 as
null_logits + (logits - null_logits) * cond_scale
According to the formula it should be
logits + (logits - null_logits) * cond_scale
where the logits are the conditional score and null_logits are the unconditional ones.

Can you please clarify the reason for this modification?
Thank you!

[nshidqi]

@MoayedHajiAli Have you found the reason?
I'm also wondering why

[tengteng95]

@nshidqi @MoayedHajiAli I also have the same question. May I ask if you have found the reason now?

[MoayedHajiAli]

Hi @tengteng95. I couldn't find the reason