why two optimizers are needed during the training?

[Wu]

Hello, thanks a lot for your hard work and your sharing.
I would like to ask why two optimizers are needed during the training.
self.optimizer.step(self.loss_func)
self.optimizer_Adam.step()

Thank you so much in advance for your answers.

[Jay Roxis]

Hi,

The original PINN uses two optimizers, Adam for initial optimization since it is generally more stable, and later use second order optimizer LBFGS for finetuning to reach higher accuracy.