A relatively common pattern I've observed is the following:
```python
_, metrics = some_jax_function()
with profiler.Trace('compute_metrics'):
jax.block_until_ready(metrics)
with profiler.Trace('copy_to_host'):
metrics = jax.device_get(metrics)
```
We are missing an opportunity here to more eagerly begin the h2d copy of
the metrics (e.g. overlap it with closing the "compute_metrics" context
manager etc. The intention of `jax.copy_to_host_async(x)` is to make it
simple to begin h2d transfers as early as possible. Adapting the above code:
```python
_, metrics = some_jax_function()
# Begin D2H copies as early as we can.
jax.copy_to_host_async(metrics)
with profiler.Trace('compute_metrics'):
jax.block_until_ready(metrics)
with profiler.Trace('copy_to_host'):
metrics = jax.device_get(metrics)
```
PiperOrigin-RevId: 731626446
Previously, we represented a missing arg name with `None`,
and a missing result path with the empty string. We now
adopt the same convention for arg names and use empty strings.
This simplifies the typing, and prevents the string "None" from
appearing in error messages.
I changed how we encode the result paths. Previously for a
function that returns a single array the path was the empty
string (the same as for an unknown path). And for a function
that returns a pair of arrays it was `([0], [1])`. Now we
add the "result" prefix: `("result",)` for a function returning a
single array and `(result[0], result[1])` for a function returning
a pair of arrays.
Finally, in debug_info_test, I removed the `check_tracer_arg_name`
so that all spied tracers are printed with the argument name they
depend on.
Callback functions should not call into JAX. This information was
missing in the docs of the callbacks. This commit adds this information
to the docs.
See: #25861, #24255
As it stands, there is only ever one element in this list (see b/384741132) and only the 0th element is ever used so we can simplify.
This is a potentially breaking change for external users, but (as stated in the [documentation](https://jax.readthedocs.io/en/latest/aot.html#debug-information-and-analyses-when-available)) no guarantees are made on this type, which is intended for debugging purposes and not intended to be a reliable public API.
PiperOrigin-RevId: 715837855
