Re-enable Z3 4.5.0 for better interpolation #536
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Thank you very much for the PR! It seems like the old Z3 version is beneficial to have. Could you also post the tables and/or quantile-plots from your experiments (for documentation purposes)? We need to make sure that there are no issues when running both Z3 instances at the same time! I'll try to start some tests in CPAchecker and report back. |
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Sure! Here are some: |
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Old versions of z3 were really good at interpolation, and I want to add support for it in JavaSMT.
To this end, I've added the implementation of a
Z3Legacysolver (to be renamed, as discussed with @baierd), which builds on the 4.5.0 release of z3, rebuilt to usecom.microsoft.z3legacyas its package name to avoid name collisions with new z3.Pre-built binaries with the modifications are available at https://github.com/leventeBajczi/z3/releases/tag/legacy-4.3.0-15644597379, which Theta already uses like this. This should be somehow integrated into the solver management of JavaSMT, which I have no experience with.
To demonstrate how good this version of Z3 is, I ran some preliminary tests in CPAchecker, and found that an NLA encoding of programs using Z3 as the interpolation solver in the predicate analysis configuration results in 510 successfully solved tasks, which are otherwise unsolved by the bitprecise encoding of the same tasks with mathsat5.
Also, I found that #381 (which I opened) is referenced in 3 of the tests, that now failed on this implementation. I removed the overly constraining line which expected the constraint IDs to be unique, which is not necessary IMO if the interpolation problem reported in that issue is otherwise handled - which it seems to be.