问题描述
我想做什么:我想调用(check-sat)，然后如果结果是unknown，调用(check-sat-using qfnra-nlsat).
What I want to do: I would like to call (check-sat), and then if the result is unknown, call (check-sat-using qfnra-nlsat).
我为什么要这样做?:对于我的应用程序，使用 (check-sat) 应用的 Z3 默认策略优于我使用 (check-sat-using).但是，在某些情况下，(check-sat) 返回 unknown，但 (check-sat-using ...) 会明智地返回选择的策略找到结果.下面是一个例子:
Why do I want to do this?: For my application the Z3 default tactics applied with (check-sat) are superior to anything I have devised using (check-sat-using). However, there are a few situations where (check-sat) returns unknown, but (check-sat-using ...) with judiciously chosen tactics finds a result. Here is an example:
(declare-fun x () Real)
(declare-fun y () Real)
(declare-fun z () Real)
(declare-fun i () Int)
(declare-fun j () Int)
(declare-fun k () Int)
(assert (= z (* x y)))
(assert (= k (* i j)))
(assert (< k z))
; This returns unknown
(check-sat)
; This gives a solution
(check-sat-using qfnra-nlsat)
(get-value (x y z i j k))
我尝试了什么?:我在单个 SMT 文件中最接近的是(check-sat-using (or-else smt qfnra-nlsat)). 不幸的是，(check-sat-using smt) 的性能不如 (check-sat)，所以这不是一个选项.
What have I tried?: The closest I've come in a single SMT file is(check-sat-using (or-else smt qfnra-nlsat)). Unfortunately (check-sat-using smt) does not perform as well as (check-sat) for my purposes, so this is not an option.
推荐答案
这不能直接使用 (check-sat)，而是 default 使用的策略 代码>(check-sat) 在这个问题之后公开.所以，在Z3当前的master分支中，可以这样写:
This is not possible directly using (check-sat), but the default tactic used by (check-sat) was exposed following this question. So, in the current master branch of Z3, it's possible to write:
(check-sat-using (or-else default qfnra-nlsat))
Z3 4.4.2 及更高版本应提供此功能.
This feature should be available with Z3 4.4.2 and greater.
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