Question about the semantics of stablehlo.scatter when unique_indices and/or indices_are_sorted are False.

[erick-xanadu]

Hello,

the specification for scatter states the following:

If indices_are_sorted is true then the implementation can assume that scatter_indices are sorted with respect to scatter_dims_to_operand_dims, otherwise the behavior is undefined.

Does this concretely mean that the behaviour is undefined if indices_are_sorted is set to False? Possibly due to the schedule being implementation defined?

If unique_indices is true then the implementation can assume that all result_index indices being scattered to are unique. If unique_indices is true but the indices being scattered to are not unique then the behavior is undefined.

The wording here makes says that the behaviour is undefined when unique_indices is true but they are not unique at runtime. But would having unique_indices be False also may be implementation defined due to schedule being implementation defined?