kohya-ss/sd-scripts

Shouldn't fix_noise_scheduler_betas_for_zero_terminal_snr be applied BEFORE prepare_scheduler_for_custom_training?

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#1905 aperta il 27 gen 2025

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Hello,

Reference code: https://github.com/kohya-ss/sd-scripts/blob/0778dd9b1df0d6aa33287ded3ce4195f3d03251b/train_network.py#L195

I noticed that fix_noise_scheduler_betas_for_zero_terminal_snr modifies the alphas_cumprod for the noise scheduler, and prepare_scheduler_for_custom_training uses alphas_cumprod to calculate all_snr. The issue with the current order is that all_snr will reflect NON-ztsnr snrs, not ztsnr, causing anything that uses all_snr to use snrs that do not align with ztsnr.

As such, shouldn't fix_noise_scheduler_betas_for_zero_terminal_snr always be applied before prepare_scheduler_for_custom_training?

Thank you.

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