Add torch.float32 support for Apple M1

[SteffenPL]

Hello,

Thanks for your amazing package!

I wanted to ask if it would be possible to provide a mechanism to use torch.float32 as dtype for some of the adaptive solvers.
On Apple M1 (mps) torch.float64 is not supported...

E.g. here

torchdiffeq/torchdiffeq/_impl/dopri5.py

Line 6 in d6ee52b

alpha=torch.tensor([1 / 5, 3 / 10, 4 / 5, 8 / 9, 1., 1.], dtype=torch.float64),

the dtype is fixed independent of the input.

I am new to your package (and also a bit to pytorch, since I usually use Julia), therefore, sorry if I was overlooking something obvious.

[hchau630]

I encountered this issue as well, but I think all you need to do is to specify options={'dtype': torch.float32} in your odeint call (assuming you're using odeint with an adaptive solver like I do).