This change only supports pinned_host -> pinned_host copies on the same device. HBM -> HBM copies don't work yet and donation also doesn't work in PJRT.
This CL also sets up the plumbing from JAX to PJRT so that in the future support for missing features can be added easily.
Fixes https://github.com/jax-ml/jax/issues/24521
PiperOrigin-RevId: 694274616
Why?
Because users need to know if an array is committed or not since JAX raises errors based on committedness of a jax.Array. JAX also makes decisions about dispatching based on committedness of a jax.Array.
But the placement of such arrays on devices is an internal implementation detail.
PiperOrigin-RevId: 686329828
Not doing the resharding, leads to incorrect outputs on GPU and a crash on TPU which is not good.
Fixes: https://github.com/google/jax/issues/23100
PiperOrigin-RevId: 665000157
This CL changes `shard_arg_handlers` to be batched, in that it now receives a list of objects and a list of shardings and returns a list of array. This makes it possible to batch backend calls whenever it's beneficial to do so.
Based on the above, the batched shard arg for arrays leverages the newly added `xla::ifrt::Client::CopyArrays()` (https://github.com/tensorflow/tensorflow/pull/69096) to make bulk copy cheaper in some backend implementations. Since `Client::CopyArrays()` requires batched arrays to have the same set of source/destination devices, `PyArray::BatchedCopyToDeviceWithSharding()` internally groups arrays by their source/destination devices and memory kinds. The grouping is pushed all the way to C++ for performance in case we have lots of arrays.
PiperOrigin-RevId: 643097852
