jax-ml/jax · error · ValueError

'order' must be either 'little' or 'big'

Error message

'order' must be either 'little' or 'big'

What it means

Raised by jnp.packbits when the bitorder argument is anything other than 'little' or 'big', which are the only two bit-ordering conventions supported.

Source

Thrown at jax/_src/numpy/lax_numpy.py:8697

    >>> a = jnp.array([[1, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0],
    ...                [0, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1]])
    >>> vals = jnp.packbits(a, axis=1)
    >>> vals
    Array([[212, 150],
           [ 69, 207]], dtype=uint8)

    The inverse of ``packbits`` is provided by :func:`~jax.numpy.unpackbits`:

    >>> jnp.unpackbits(vals, axis=1)
    Array([[1, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0],
           [0, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1]], dtype=uint8)
  """
  arr = util.ensure_arraylike("packbits", a)
  if not (issubdtype(arr.dtype, np.integer) or issubdtype(arr.dtype, np.bool_)):
    raise TypeError('Expected an input array of integer or boolean data type')
  if bitorder not in ['little', 'big']:
    raise ValueError("'order' must be either 'little' or 'big'")
  arr = lax.ne(arr, lax._const(arr, 0)).astype('uint8')
  bits = arange(8, dtype='uint8')
  if bitorder == 'big':
    bits = bits[::-1]
  if axis is None:
    arr = ravel(arr)
    axis = 0
  arr = swapaxes(arr, axis, -1)

  remainder = arr.shape[-1] % 8
  if remainder:
    arr = lax.pad(arr, np.uint8(0),
                  (arr.ndim - 1) * [(0, 0, 0)] + [(0, 8 - remainder, 0)])

  arr = arr.reshape(arr.shape[:-1] + (arr.shape[-1] // 8, 8))
  bits = expand_dims(bits, tuple(range(arr.ndim - 1)))
  packed = (arr << bits).sum(-1).astype('uint8')
  return swapaxes(packed, axis, -1)

View on GitHub (pinned to 1e1c6a8fc0)

Solutions

1. Use exactly 'little' or 'big' (case-sensitive)
2. Map external config values to the allowed strings, defaulting sensibly
3. Add a validation/default at the config layer: order = order or 'big'

Example fix

// before
jnp.packbits(a, bitorder='big-endian')
// after
jnp.packbits(a, bitorder='big')

assert bitorder in ('little', 'big'), "bitorder must be 'little' or 'big'"

def valid_bitorder(order):
    return order in ('little', 'big')

When it happens

Trigger: jnp.packbits(a, bitorder='msb') or 'MSB'/'big-endian'; passing an enum/None; typos like 'Big'.

Common situations: Confusing bitorder with byteorder terminology from struct/numpy dtype ('>'/'<'); case-sensitive values from config files; default None from an optional parameter threaded through.

Related errors

• `compute_on`'s compute_type argument must be a string.
• Argument '{x}' of type '{typ}' is not a valid JAX type
• Argument '{arg}' of type {type(arg)} is not a valid JAX type
• Expected kind to be a dtype, string, or tuple; got {kind=}
• at least one array or dtype is required

AI-assisted analysis of jax-ml/jax@1e1c6a8fc0 (2026-08-27). Data as JSON: /api/errors/2d0956826487d551. Report an issue: GitHub.