[JAX] Replace uses of jax.devices("cpu") with jax.local_devices(backe…

…nd="cpu").

An upcoming change to JAX will include non-local (addressable) CPU devices in jax.devices() when JAX is used multicontroller-style, where there are multiple Python processes.

This change preserves the current behavior by replacing uses of jax.devices("cpu"), which previously only returned local devices, with jax.local_devices("cpu"), which will return local devices both now and in the future.

This change is always be safe (i.e., it should always preserve the previous behavior) but it may sometimes be unnecessary if code is never used in a multicontroller setting.

PiperOrigin-RevId: 583072300
Change-Id: I128aa11d48a8dd89103dbec6f273e19963820b77

acme/agents/jax/pwil/rewarder.py

@@ -63,8 +63,10 @@ def __init__(self,
     self._std = (self._std < 1e-6) + self._std
 
     self.expert_atoms = self._vectorized_demonstrations / self._std
-    self._compute_norm = jax.jit(lambda a, b: jnp.linalg.norm(a - b, axis=1),
-                                 device=jax.devices('cpu')[0])
+    self._compute_norm = jax.jit(
+        lambda a, b: jnp.linalg.norm(a - b, axis=1),
+        device=jax.local_devices(backend='cpu')[0],
+    )
 
   def _vectorize(self,
                  demonstrations_it: Iterator[types.Transition]) -> np.ndarray: