Examples with ArithExpr com.microsoft.z3.ArithExpr used on opensource projects

Example 21 with ArithExpr

use of com.microsoft.z3.ArithExpr in project batfish by batfish.

the class EncoderSlice method addUnusedDefaultValueConstraints.

/*
   * For performance reasons, we add constraints that if a message is not
   * valid, then the other variables will use default values. This speeds
   * up the solver significantly.
   */
private void addUnusedDefaultValueConstraints() {
    for (SymbolicRoute vars : getAllSymbolicRecords()) {
        BoolExpr notPermitted = mkNot(vars.getPermitted());
        ArithExpr zero = mkInt(0);
        if (vars.getAdminDist() != null) {
            add(mkImplies(notPermitted, mkEq(vars.getAdminDist(), zero)));
        }
        if (vars.getMed() != null) {
            add(mkImplies(notPermitted, mkEq(vars.getMed(), zero)));
        }
        if (vars.getLocalPref() != null) {
            add(mkImplies(notPermitted, mkEq(vars.getLocalPref(), zero)));
        }
        if (vars.getPrefixLength() != null) {
            add(mkImplies(notPermitted, mkEq(vars.getPrefixLength(), zero)));
        }
        if (vars.getMetric() != null) {
            add(mkImplies(notPermitted, mkEq(vars.getMetric(), zero)));
        }
        if (vars.getOspfArea() != null) {
            add(mkImplies(notPermitted, vars.getOspfArea().isDefaultValue()));
        }
        if (vars.getOspfType() != null) {
            add(mkImplies(notPermitted, vars.getOspfType().isDefaultValue()));
        }
        if (vars.getProtocolHistory() != null) {
            add(mkImplies(notPermitted, vars.getProtocolHistory().isDefaultValue()));
        }
        if (vars.getBgpInternal() != null) {
            add(mkImplies(notPermitted, mkNot(vars.getBgpInternal())));
        }
        if (vars.getClientId() != null) {
            add(mkImplies(notPermitted, vars.getClientId().isDefaultValue()));
        }
        if (vars.getIgpMetric() != null) {
            add(mkImplies(notPermitted, mkEq(vars.getIgpMetric(), zero)));
        }
        if (vars.getRouterId() != null) {
            add(mkImplies(notPermitted, mkEq(vars.getRouterId(), zero)));
        }
        vars.getCommunities().forEach((cvar, e) -> add(mkImplies(notPermitted, mkNot(e))));
    }
}

Example 22 with ArithExpr

use of com.microsoft.z3.ArithExpr in project batfish by batfish.

the class PropertyAdder method instrumentLoad.

/*
   * Instruments the network with load balancing information to destination
   * port for graph edge ge. Each router will split load according to the
   * number of neighbors it actively uses to get to ge.
   */
Map<String, ArithExpr> instrumentLoad(Set<GraphEdge> ges) {
    Context ctx = _encoderSlice.getCtx();
    Solver solver = _encoderSlice.getSolver();
    String sliceName = _encoderSlice.getSliceName();
    Map<String, ArithExpr> loadVars = new HashMap<>();
    Graph graph = _encoderSlice.getGraph();
    for (String router : graph.getRouters()) {
        String name = _encoderSlice.getEncoder().getId() + "_" + sliceName + "_load_" + router;
        ArithExpr var = ctx.mkIntConst(name);
        loadVars.put(router, var);
        _encoderSlice.getAllVariables().put(var.toString(), var);
    }
    loadVars.forEach((name, var) -> solver.add(ctx.mkGe(var, ctx.mkInt(0))));
    ArithExpr zero = ctx.mkInt(0);
    ArithExpr one = ctx.mkInt(1);
    for (Entry<String, List<GraphEdge>> entry : graph.getEdgeMap().entrySet()) {
        String router = entry.getKey();
        List<GraphEdge> edges = entry.getValue();
        ArithExpr load = loadVars.get(router);
        BoolExpr hasDirectRoute = ctx.mkFalse();
        BoolExpr isAbsorbed = ctx.mkFalse();
        SymbolicRoute r = _encoderSlice.getBestNeighborPerProtocol(router, Protocol.CONNECTED);
        for (GraphEdge ge : edges) {
            if (!ge.isAbstract() && ges.contains(ge)) {
                // if we leave the network
                if (ge.getPeer() == null) {
                    BoolExpr fwdIface = _encoderSlice.getForwardsAcross().get(ge.getRouter(), ge);
                    assert (fwdIface != null);
                    hasDirectRoute = ctx.mkOr(hasDirectRoute, fwdIface);
                }
                // if connected route and we use it despite not forwarding
                if (r != null) {
                    BitVecExpr dstIp = _encoderSlice.getSymbolicPacket().getDstIp();
                    BitVecExpr ip = ctx.mkBV(ge.getStart().getAddress().getIp().asLong(), 32);
                    BoolExpr reach = ctx.mkAnd(r.getPermitted(), ctx.mkEq(dstIp, ip));
                    isAbsorbed = ctx.mkOr(isAbsorbed, reach);
                }
            }
        }
        ArithExpr acc = ctx.mkInt(0);
        for (GraphEdge edge : edges) {
            if (!edge.isAbstract()) {
                BoolExpr fwd = _encoderSlice.getForwardsAcross().get(router, edge);
                assert (fwd != null);
                if (edge.getPeer() != null) {
                    ArithExpr peerLoad = loadVars.get(edge.getPeer());
                    ArithExpr x = (ArithExpr) ctx.mkITE(fwd, peerLoad, zero);
                    acc = ctx.mkAdd(acc, x);
                }
            }
        }
        solver.add(ctx.mkEq(load, acc));
        BoolExpr guard = _encoderSlice.mkOr(hasDirectRoute, isAbsorbed);
        BoolExpr cond = _encoderSlice.mkIf(guard, ctx.mkEq(load, one), ctx.mkEq(load, acc));
        solver.add(cond);
    }
    return loadVars;
}

Example 23 with ArithExpr

use of com.microsoft.z3.ArithExpr in project batfish by batfish.

the class PropertyAdder method initializeReachabilityVars.

/*
   * Initialize reachability and id variables an add the constraints
   * that all ids are at least 0 or higher, and reachable means non-zero.
   */
private void initializeReachabilityVars(EncoderSlice slice, Context ctx, Solver solver, Map<String, BoolExpr> reachableVars, Map<String, ArithExpr> idVars) {
    String sliceName = slice.getSliceName();
    ArithExpr zero = ctx.mkInt(0);
    for (String r : _encoderSlice.getGraph().getRouters()) {
        int id = _encoderSlice.getEncoder().getId();
        String s1 = id + "_" + sliceName + "_reachable-id_" + r;
        String s2 = id + "_" + sliceName + "_reachable_" + r;
        ArithExpr idVar = ctx.mkIntConst(s1);
        BoolExpr var = ctx.mkBoolConst(s2);
        idVars.put(r, idVar);
        reachableVars.put(r, var);
        _encoderSlice.getAllVariables().put(idVar.toString(), idVar);
        _encoderSlice.getAllVariables().put(var.toString(), var);
        solver.add(ctx.mkEq(var, ctx.mkGt(idVar, zero)));
        solver.add(ctx.mkGe(idVar, zero));
    }
}

Example 24 with ArithExpr

use of com.microsoft.z3.ArithExpr in project batfish by batfish.

the class PropertyAdder method instrumentReachability.

/*
   * Also instruments reachability, but to a destination router
   * rather than a destination port.
   */
Map<String, BoolExpr> instrumentReachability(String router) {
    Context ctx = _encoderSlice.getCtx();
    Solver solver = _encoderSlice.getSolver();
    Map<String, BoolExpr> reachableVars = new HashMap<>();
    Map<String, ArithExpr> idVars = new HashMap<>();
    initializeReachabilityVars(_encoderSlice, ctx, solver, reachableVars, idVars);
    ArithExpr baseId = idVars.get(router);
    _encoderSlice.add(ctx.mkEq(baseId, ctx.mkInt(1)));
    Graph g = _encoderSlice.getGraph();
    for (Entry<String, List<GraphEdge>> entry : g.getEdgeMap().entrySet()) {
        String r = entry.getKey();
        List<GraphEdge> edges = entry.getValue();
        if (!r.equals(router)) {
            ArithExpr id = idVars.get(r);
            BoolExpr cond = recursiveReachability(ctx, _encoderSlice, edges, idVars, r, id);
            solver.add(cond);
        }
    }
    return reachableVars;
}

Example 25 with ArithExpr

use of com.microsoft.z3.ArithExpr in project batfish by batfish.

the class PropertyChecker method checkLoadBalancing.

/*
   * Computes whether load balancing for each source node in a collection is
   * within some threshold k of the each other.
   */
public AnswerElement checkLoadBalancing(HeaderLocationQuestion q, int k) {
    return checkProperty(q, (enc, srcRouters, destPorts) -> {
        PropertyAdder pa = new PropertyAdder(enc.getMainSlice());
        Map<String, ArithExpr> loads = pa.instrumentLoad(destPorts);
        Map<String, BoolExpr> prop = new HashMap<>();
        // TODO: implement this properly after refactoring
        loads.forEach((name, ae) -> prop.put(name, enc.mkTrue()));
        return prop;
    }, (vp) -> new SmtOneAnswerElement(vp.getResult()));
}