Z3 FP logic: produces unexpected model

问题

For this problem: http://rise4fun.com/Z3/YNBG

Z3 produces the model:

sat
((s0 FP!val!0))

I was expecting to see a true number as the model. It's almost as if it's treating FP as an uninterpreted sort for this case. Is there a way to get Z3 to produce a real number here?

回答1:

Thanks for reporting this. Indeed, there was a bug in the model completion for FPA. The fix is already available in the unstable branch at Codeplex.

Note that == (floating point equal) with NaN is always false, i.e., in this example, any s0 satisfies the formula. Such values are now correctly omitted at all (in get-model) or the model is completed with a NaN (for get-value or generally when model completion is enabled).

来源：https://stackoverflow.com/questions/15737340/z3-fp-logic-produces-unexpected-model