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Handle PRNG keys in reshard by using jax.device_put. #120

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Merged
copybara-service merged 1 commit into from
Oct 3, 2025
Merged

Handle PRNG keys in reshard by using jax.device_put. #120

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29 changes: 17 additions & 12 deletions pathwaysutils/experimental/reshard.py
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Original file line number Diff line number Diff line change
Expand Up @@ -150,24 +150,27 @@ def reshard(
# put them back together in the right order.
array_info_lambda = lambda: {"arrays": [], "indices": [], "dst_shardings": []}
jax_arrays = collections.defaultdict(array_info_lambda)
non_jax_arrays = array_info_lambda()
non_reshardable_arrays = array_info_lambda()
for index, (arr, dst_sharding) in enumerate(zip(flat_x, flat_sharding)):
if not isinstance(dst_sharding, jax.sharding.Sharding):
raise ValueError("`sharding` must contain only `jax.sharding.Sharding`")
if isinstance(arr, jax.Array):
if not isinstance(arr, jax.Array) or (
hasattr(arr, "dtype")
and jax.dtypes.issubdtype(arr.dtype, jax.dtypes.prng_key)
):
non_reshardable_arrays["arrays"].append(arr)
non_reshardable_arrays["indices"].append(index)
non_reshardable_arrays["dst_shardings"].append(dst_sharding)
else:
device_set = frozenset(arr.sharding.device_set)
jax_arrays[device_set]["arrays"].append(arr)
jax_arrays[device_set]["indices"].append(index)
jax_arrays[device_set]["dst_shardings"].append(dst_sharding)
else:
non_jax_arrays["arrays"].append(arr)
non_jax_arrays["indices"].append(index)
non_jax_arrays["dst_shardings"].append(dst_sharding)

if non_jax_arrays["arrays"]:
non_jax_arrays["arrays"] = jax.device_put(
non_jax_arrays["arrays"],
non_jax_arrays["dst_shardings"],

if non_reshardable_arrays["arrays"]:
non_reshardable_arrays["arrays"] = jax.device_put(
non_reshardable_arrays["arrays"],
non_reshardable_arrays["dst_shardings"],
donate=donate,
may_alias=may_alias,
)
Expand All @@ -186,7 +189,9 @@ def reshard(
).execute(tuple(array_info["arrays"]))

result = [None] * len(flat_x)
for arr, idx in zip(non_jax_arrays["arrays"], non_jax_arrays["indices"]):
for arr, idx in zip(
non_reshardable_arrays["arrays"], non_reshardable_arrays["indices"]
):
result[idx] = arr
for array_info in jax_arrays.values():
for arr, idx in zip(array_info["arrays"], array_info["indices"]):
Expand Down