@jdsteve2 The case that's caught by this could be causing you accuracy grief in the modeling. (not very likely, but worth it to rule out)

@inducer Initially this seems to be giving me that ValueError when I try to evaluate the 0 polynomial. Should it do that?

>>> import islpy as isl
>>> poly = isl.PwQPolynomial('{ 0 }')
>>> param_dict = dict(n=128)
>>> poly.eval_with_dict(param_dict)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jdsteve2/src/islpy/islpy/__init__.py", line 691, in pwqpolynomial_eval_with_dict
    raise ValueError("evaluation point outside of domain of "
ValueError: evaluation point outside of domain of definition of piecewise quasipolynomial

(also, this did help me find some incorrect assumptions in a few kernels, thanks!)

Initially this seems to be giving me that ValueError when I try to evaluate the 0 polynomial. Should it do that?

For the zero polynomial with the empty domain: yes. You'll probably need to construct a zero polynomial with the universe as its domain.

Fwiw, in cases where assumptions were violated, this would (sometimes) silently evaluate to zero, leading to totally bogus results. Embarrassingly, this happened for the first time in a noticeable way while I was demoing something for Paul F...