This seems like a tricky problem to solve. I think a practical use of constraint solvers would have some criteria by which a solution would be seen as desirable

This seems like a tricky problem to solve. I think a practical use of constraint solvers would have some criteria by which a solution would be seen as desirable. For eg if I’m designing something in the real world I’d want to optimize for material or cost in terms of time or money. Sometimes I’m just interested in seeing if a solution exists. So the solution here seems to be able to add soft constraints on what kinds of solutions are desired to guide the search.