lr_cooler and clip_cooler doesn't work correctly

[kngwyu]

Rainy/rainy/config.py

Line 157 in 21987a3

def lr_cooler(self, initial: float) -> Cooler:

They subtracts (initial - minimum) / max_steps from the value every time they're called, but they are called only max_steps / (nstpes * nworkers) times in A2C, PPO and ACKTR.

This should be fixed and the benchmark in #8 should be done again.