MAINT, ENH: concision of ufunc type/dims "dispatching"

[tylerjereddy]

One of the concerns @gliga brought up in gh-124 code review was the lack of concision in the ufunc dispatching to workunits with regard to data types and view dimensionality--we are currently quite verbose in checking first the string name of the data type of a view and then its shape/dimensionality, before manually calling out to a workunit for that particular dimensionality and type + functionality.

One possible solution I "pitched" to Nader and Neil at the PyKokkos meeting this morning was the usage of the Python standard library inspect module to obtain a list of function names for workunits/kernels, that we could then dispatch to using some templating/string logic.

In fact, we already use a strategy similar to this to call/pre-compile most of our ufunc workunits in pre_compile_tools/pre_compile_ufuncs.py, to avoid hypothesis timeout failures related to our slow compile times when running the array API standard conformance suite.

So, very roughly/crudely, we might do something like:

from inspect import getmembers, isfunction
from pykokkos.lib import ufuncs

kernel_dict = dict(getmembers(ufuncs, isfunction))
# should be a dictionary with structure similar to:
# {function_name (string): function_object (actual workunit object)}

# workunit sketch/pseudocode

def round(view):
    out = pk.View(...)
    ndims = view.ndims
    dtype = view.dtype
    op = "round"
    # workunits are currently named like: round_impl_1d_double
    function_name_str = f"{op}_impl_{ndims}d_{dtype}"
    desired_workunit = kernel_dict[function_name_str]
    # call the kernel
    desired_workunit(tid, view, out)

Of course, this is just a pseudocode prototype, and may require some careful thought/refactoring--for example, we may want to rename workunit functions or adjust call signatures a bit for templating/dispatching convenience, and probably also separate the workunits to a separate module so we get easy access to the dictionary of function_name:function_object on import, etc.