Extended fix OOM Issue #21634 on Keras side

keras/src/backend/jax/distribution_lib.py

@@ -246,3 +246,120 @@ def _to_backend_layout(tensor_layout):
     partition_spec = jax.sharding.PartitionSpec(*tensor_layout.axes)
     jax_mesh = tensor_layout.device_mesh.backend_mesh
     return jax.sharding.NamedSharding(jax_mesh, partition_spec)
+
+
+def _distribute_initializer(
+    init_func=None, mean=0.0, stddev=1.0, seed=None, layout=None
+):
+    """
+    Distribution-aware token embedding initializer for JAX backend.
+
+    This function will create a Jax random array and
+    distribute it according to the current token embedding layout.
+
+    Args:
+        init_func: A functools.partial-wrapped object that takes the seed
+            as argument and returns a jax.Array. Must have shape and dtype
+            already bound via partial.
+        mean: Mean of distribution (applied to normal/truncated_normal).
+        stddev: Standard deviation of the distribution.
+        seed: Random seed for initialization.
+        layout: TensorLayout for the distributed tensor.
+
+    Returns:
+        A distributed jax array.
+
+    Raises:
+        ValueError: If init_func or seed is None.
+                    If init_func.func is not a supported random function.
+                    Supported jax.random func: normal, truncated_normal, uniform
+        TypeError: If init_func is not a functools.partial object.
+    """
+    import warnings
+    from functools import partial
+
+    # Create SeedGenerator to ensure backend variable exists
+    # For future state tracking for distributed keys, add
+    # attributes for base/split keys and number of devices sharded.
+    if isinstance(seed, jax.Array):
+        seed_gen = seed_generator.SeedGenerator(seed=int(seed[0]))
+    elif isinstance(seed, int):
+        seed_gen = seed_generator.SeedGenerator(seed=seed)
+    elif isinstance(seed, seed_generator.SeedGenerator):
+        seed_gen = seed
+    else:
+        raise ValueError(
+            f"seed must be int, JAX array, or SeedGenerator, got {type(seed)}"
+        )
+
+    # Extract the state value as JAX array
+    jax_seed = seed_gen.state.value
+
+    # Convert to JAX PRNG key format (swap counter and seed value)
+    jax_compatible_seed = jax.numpy.array(
+        [jax_seed[1], jax_seed[0]], dtype=jax.numpy.uint32
+    )
+
+    # Validate all required arguments
+    if init_func is None or init_func.func.__name__ not in [
+        "normal",
+        "truncated_normal",
+        "uniform",
+    ]:
+        raise ValueError(
+            "init_func cannot be None or "
+            "Unsupported initializer: {init_func.func.__name__}."
+            "only JAX-compatible random initializers are supported. "
+            "Supported jax.random funcs: normal, truncated_normal, uniform"
+        )
+
+    # Ensure init_func is a partial
+    if not isinstance(init_func, partial):
+        raise TypeError(
+            f"init_func must be functools.partial object, got {type(init_func)}"
+            "init_func is a jax.random.* function with shape and "
+            "dtype bound via partial"
+        )
+
+    # Shard based on tensor layout
+    if layout is None:
+        warnings.warn(
+            f"The layout is {layout}, sharding will default to single device"
+        )
+        sharding = None
+    else:
+        sharding = _to_backend_layout(layout)
+
+    # JAX PRNG key handling within JIT:
+    # The key is passed directly to jax.random.* functions which are
+    # JIT-compatible and functional. JAX automatically ensures different
+    # random values per shard when out_shardings is specified.
+    try:
+        compiled_init = jax.jit(
+            lambda jax_compatible_seed: init_func(jax_compatible_seed),
+            out_shardings=sharding,
+        )
+        sample = compiled_init(jax_compatible_seed)
+    except RuntimeError as e:
+        warnings.warn(
+            f"Sharding failed due to: {e}, falling back to single device"
+        )
+        compiled_init = jax.jit(
+            lambda jax_compatible_seed: init_func(jax_compatible_seed),
+            out_shardings=None,
+        )
+        sample = compiled_init(jax_compatible_seed)
+
+    # Store the SeedGenerator for state tracking
+    seed = seed_gen.next()
+
+    # Apply mean/stddev only for distributions where it makes sense
+    if init_func.func in (jax.random.normal, jax.random.truncated_normal):
+        return sample * stddev + mean
+    elif init_func.func == jax.random.uniform:
+        # Uniform doesn't use mean/stddev - warn
+        if mean != 0.0 or stddev != 1.0:
+            warnings.warn(
+                "mean and stddev are ignored for uniform distribution"
+            )
+        return sample