зеркало из https://github.com/microsoft/mcBV.git
648 строки
28 KiB
Forth
648 строки
28 KiB
Forth
module Trail
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open Util
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open Stats
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open Interval
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open GlobalOptions
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open BitVector
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open Literal
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open Clause
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open BooleanValuation
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open BitVectorValuation
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open BoundsValuation
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open Database
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open Learning
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let bumpOrder (db:Ref<Database>) (v:Var) =
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//(!(!db).Variables).varOrder.bump v
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if (!(!db).Theory).isDefined v then
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let tRel = (!(!db).Theory).getThRelation v
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for a in tRel.variableArguments do
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(!(!db).Variables).varOrder.bump a
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[<NoComparison>]
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type TrailElement =
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| BAssgnmnt of Var*(Literal*Literal)*Interval // Bounds Assignment: BvVar, (previous l expl, previous u expl), previous interval
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| MAssgnmnt of Var*Literal*BitVector // Model Assignment: BvVar, prevBoolExplanation, prevBVset, previous order
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| BoolDecision of Literal
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| Imp of Ref<Clause>*Literal
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let isImplication (e:TrailElement) =
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match e with
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| Imp _ -> true
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| _ -> false
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let isBoolLiteral (e:TrailElement) =
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match e with
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| BAssgnmnt _
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| MAssgnmnt _ -> false
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| _ -> true
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let getBoolLiteral (e:TrailElement) =
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assert(isBoolLiteral e)
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match e with
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| BoolDecision l -> l
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| Imp (c, l) -> l
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| _ -> 0
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let getBVVar (e:TrailElement) =
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assert(not (isBoolLiteral e))
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match e with
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| MAssgnmnt (v,_,_) -> v
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| BAssgnmnt (v,_,_) -> v
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| _ -> 0
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let updateVarOrder (db:Ref<Database>) (v:Var) =
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(!(!db).Variables).varOrder.suspend v
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if (!(!db).Theory).isDefined v then
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let t = (!(!db).Theory).getThRelation v
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let vars = t.variableArguments
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for bv in vars do
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(!(!db).Variables).varOrder.bump bv
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type Trail (sz:int) =
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let mutable size = sz //Allocated space
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let mutable topPtr = 0 //Elements on the trail
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let mutable trailPtr = 0 //Next element to propagate
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let mutable printCount = 0
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let mutable numDecisions = 0
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let mutable numAssignments = 0
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let nullClause = [|0|]
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member r.hasPropagationsPending = trailPtr < topPtr
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member r.getCount = topPtr
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member val trail:TrailElement array = Array.create size (BoolDecision 0) with get, set
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member r.getTrailPtr = trailPtr
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member r.nextPropagation =
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assert(r.hasPropagationsPending) //Safe only if hasPropagationPending returns true
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let l = r.trail.[trailPtr]
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trailPtr <- trailPtr + 1
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l
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member r.lastPropagation =
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assert(trailPtr>0)
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r.trail.[trailPtr - 1]
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member r.propagationDone =
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trailPtr <- trailPtr + 1
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member r.getNumDecisions = numDecisions
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member r.getLiteral(i:int) : Literal =
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if i <= topPtr then
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match r.trail.[i] with
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|BoolDecision l -> l
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|Imp (_,l) -> l
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|_->(0:Literal)
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else
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(0:Literal)
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member r.getExplanation(i:int) : Ref<Clause> =
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if i < topPtr then
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match r.trail.[i] with
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|Imp (e, l) -> e
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|_-> ref nullClause
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else
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ref nullClause
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member r.get(i:int):TrailElement option =
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if i < topPtr then
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Some (r.trail.[i])
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else
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None
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member r.realloc()=
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r.trail <- Array.append r.trail (Array.create size (BoolDecision 0))
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size<- 2*size
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member r. ElementToString (e:TrailElement) =
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match e with
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// | BAssgnmnt (v,_,_) -> "BA" + v.ToString()
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// | MAssgnmnt (v,_,_,_) -> "MA " + v.ToString()
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| BoolDecision l -> "no reason"
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| Imp (e,l) -> (clauseToString (!e)) + " -> " + (l.ToString())
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| _ -> ""
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member private r.pushElement (e:TrailElement) =
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if topPtr >= size then
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r.realloc()
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r.trail.[topPtr]<-e
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topPtr <- topPtr + 1
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member r.Push (bVal:Ref<BooleanValuation>)
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(bvVal:Ref<BitVectorValuation>)
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(bounds:Ref<BoundsValuation>)
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(db:Ref<Database>)
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(stats:Ref<Statistics>)
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(e:TrailElement) =
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match e with
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| BoolDecision l ->
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assert ((!bVal).getValueB l = Undefined)
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numDecisions <- numDecisions + 1
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(!bVal).setValueB l r.getNumDecisions |> ignore
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(!stats).Decision()
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updateVarOrder db (lit2var l)
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dbg <| (lazy sprintf "> Decision: %d!" l)
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r.pushElement (BoolDecision l)
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| Imp (cRef, l) ->
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assert ((!bVal).getValueB l = Undefined)
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assert (Array.exists (fun x -> x = 0) !cRef = false)
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assert ((!cRef).[1] = l) // CMW: Required for soundness of Boolean conflict resolution.
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(!bVal).setValueB l r.getNumDecisions |> ignore
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updateVarOrder db (lit2var l)
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(!stats).Implication()
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verbose <| (lazy sprintf " | ==> %d (because of %s)" l (clauseToString !cRef))
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r.pushElement (Imp (cRef, l))
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| MAssgnmnt (v, r, value) ->
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if ((!bvVal).getValue v).isConcreteValue then
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(!(!db).Variables).varOrder.suspend v
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| BAssgnmnt _->
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() //AZ: All the necessary book-keeping has been done beforehand in pushMA,
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// at this point their role is to trigger visitOccurences in propagation.
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match e with
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| BoolDecision l
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| Imp (_, l) -> r.pushMA l bVal bvVal bounds db stats
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| _ -> None
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member private r.popElement () =
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assert (topPtr > 0)
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//r.dbgPrint ("Pop: " + (trailElem2String r.trail.[topPtr - 1]))
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topPtr <- topPtr - 1
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match r.trail.[topPtr] with
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| BoolDecision _ ->
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numDecisions <- numDecisions - 1
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assert(numDecisions >= 0)
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| MAssgnmnt _ -> ()
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| BAssgnmnt _ -> ()
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| _ -> ()
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if trailPtr > topPtr then
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trailPtr <- topPtr
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r.trail.[topPtr]
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member r.Pop (bVal:Ref<BooleanValuation>)
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(pAss:Ref<BitVectorValuation>)
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(bounds:Ref<BoundsValuation>)
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(db:Ref<Database>) =
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let e = r.popElement ()
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if TRC then
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r.print ("Pop : "+ (r.ElementToString e), pAss, bounds)
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match e with
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| MAssgnmnt (bvVar, oldExplain, oldValue) ->
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assert (bvVar <> 0)
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if oldValue.Length <> 0 then // normal model assignment.
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if ((!pAss).getValue bvVar).isConcreteValue then
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assert (not oldValue.isConcreteValue)
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(!(!db).Variables).varOrder.restore bvVar
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(!pAss).mAssignmntsExplanations.[bvVar] <- oldExplain
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(!pAss).setValue bvVar oldValue
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| BAssgnmnt (bvVar, (oldLExplain, oldUExplain), oldBounds) ->
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assert (bvVar <> 0)
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(!bounds).L_explanation.[bvVar] <- oldLExplain
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(!bounds).U_explanation.[bvVar] <- oldUExplain
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(!bounds).set bvVar oldBounds
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| BoolDecision l ->
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(!bVal).resetValueTAboveCurrentDecisionLevel r.getNumDecisions
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assert (l <> 0)
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(!bVal).resetVal (lit2var l) |> ignore
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(!(!db).Variables).varOrder.restore (lit2var l)
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| Imp (_,l) ->
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assert (l <> 0)
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(!bVal).resetVal (lit2var l) |> ignore
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(!(!db).Variables).varOrder.restore (lit2var l)
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member r.Reset() = topPtr <- 0
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trailPtr <- 0
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member r.printClsOrCubeVerbose (db:Ref<Database>)
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(connective:string)
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(clause:Ref<Clause>)
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=
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for j in 1 .. (!clause).[0] do
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let i = (!clause).[j]
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let v = (lit2var i)
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if j <> 1 then printf " "
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if (!(!db).Theory).isDefined v then
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if i < 0 then
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printf "-"
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else
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printf " "
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printf "%s" (((!(!db).Theory).getThRelation v).ToString((!db).Numerals))
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else
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printf "%d" i
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printf " (L %02d)" (r.getLevelExpensive v)
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if j < (!clause).[0] then
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printfn " %s " connective
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printfn ""
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member r.printClauseVerbose (db:Ref<Database>) (clause:Ref<Clause>) =
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r.printClsOrCubeVerbose db "\/" clause
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member r.printCubeVerbose (db:Ref<Database>) (cube:Ref<Clause>) =
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r.printClsOrCubeVerbose db "/\\" cube
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member r.print (s:string, bvVal:Ref<BitVectorValuation>, bounds:Ref<BoundsValuation>) =
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if VRB && printCount % 10000 = 0 then
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r.forcePrint (s, bvVal, bounds)
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printCount <- printCount + 1
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member r.forcePrint (s:string, bvVal:Ref<BitVectorValuation>, bounds:Ref<BoundsValuation>) =
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printfn "%s" s
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let mutable lvl = 0
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printfn "==================================================="
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printfn "L %02d ----------------------------------------------" lvl
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for i in 0 .. topPtr - 1 do
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if i = trailPtr then
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printfn " <---- "
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match r.trail.[i] with
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| MAssgnmnt (var, oe,_) ->
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//lvl <- lvl + 1
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let mutable reason = (!bvVal).mAssignmntsExplanations.[var].ToString()
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let mutable value = ((!bvVal).getValue var).ToString()
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let mutable j = i + 1
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while j < topPtr - 1 do
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match r.trail.[j] with
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| MAssgnmnt(v, oldexpl, oldval) when v = var ->
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value <- oldval.ToString()
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reason <- oldexpl.ToString()
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j <- topPtr
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| _ -> ()
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j <- j + 1
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printfn " [%s] <-> %d:bv = %s " reason var value
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| BAssgnmnt (var, (oLe, oUe), oldBounds) ->
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let mutable lE = (!bounds).L_explanation.[var].ToString()
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let mutable uE = (!bounds).U_explanation.[var].ToString()
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let mutable intvl = ((!bounds).get var).ToString()
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let mutable j = i + 1
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while j < topPtr - 1 do
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match r.trail.[j] with
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| BAssgnmnt(v, (oldL, oldU), oldintvl) when v = var ->
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intvl <- oldintvl.ToString()
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lE <- oldL.ToString()
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uE <- oldU.ToString()
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j <- topPtr
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| _ -> ()
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j <- j + 1
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printfn " [%s /\ %s] <-> %d:bv \in %s " lE uE var intvl
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| BoolDecision l ->
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lvl <- lvl + 1
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printfn "L %02d ----------------------------------------------" lvl
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printfn " * %d" l
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| Imp (e,l) -> printfn " %s -> %s " (clauseToString !e) (l.ToString())
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printfn "==================================================="
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member r.getLevelExpensive (l:Literal) =
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let var = lit2var(l)
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let mutable found = false
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let mutable i = 0
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let mutable lvl = 0
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while (not found && i < r.getCount) do
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match r.trail.[i] with
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| Imp(_, m) -> if var = lit2var(m) then found <- true
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| MAssgnmnt(v, _,_) -> if v = var then found <- true
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| BAssgnmnt(v, _, _) -> if v = var then found <- true
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| BoolDecision m ->
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if var = (lit2var m) then
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found <- true
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lvl <- lvl + 1
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i <- i + 1
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lvl
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member private r.makeRLEMA (bv:Var, newExpl:Var, newPttrn:BitVector)
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(pAss:Ref<BitVectorValuation>)
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(bounds:Ref<BoundsValuation>)
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(db:Ref<Database>)
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(stats:Ref<Statistics>) =
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let oldPttrn = (!pAss).getValue bv
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let oldExpl = (!pAss).mAssignmntsExplanations.[bv]
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let oldBounds = (!bounds).get bv
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let intrsctn = (BitVector.Intersect newPttrn oldPttrn)
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if intrsctn.isInvalid then
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// Bounds implied model assignment violating a bitpattern
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// CMW: Definitely always cross-theory?
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// AZ: Yes, if a value is invalid within single theory
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// it wouldn't try to make an assignment.
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let cls = collectLiterals [ Negate newExpl; Negate oldExpl ]
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(None, Some (ref (newClauseFromList cls)))
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elif intrsctn.isConcreteValue && not (oldBounds.Contains intrsctn) then
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// Bit-pattern implied assignment violates bounds
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let violatedBound = if not (BitVector.bvULEQ intrsctn oldBounds.Upper) then
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(!bounds).U_explanation.[bv]
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else
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(!bounds).L_explanation.[bv]
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let cls = collectLiterals [ Negate newExpl; Negate oldExpl; Negate violatedBound ]
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(None, Some (ref (newClauseFromList cls)))
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else
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let value_is_a_subset = (BitVector.bvEQ newPttrn intrsctn)
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if value_is_a_subset then
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(!pAss).setValue bv newPttrn
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(!pAss).mAssignmntsExplanations.[bv] <- newExpl
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(!stats).ModelAssignment()
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if newPttrn.isConcreteValue then
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(!(!db).Variables).varOrder.suspend bv
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trace <| (lazy sprintf " | ==> %d:bv = %s (because of %d)" bv (newPttrn.ToString()) newExpl)
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(Some (MAssgnmnt (bv, oldExpl, oldPttrn)), None)
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elif not (BitVector.bvEQ newPttrn oldPttrn) then
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// CMW: In this case we may still be able to "learn" something, but it doesn't
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// have the shape of an RLE expression, but a nice regular expression might exist.
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(None, None)
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else
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// This can happen when a Boolean variable gets activated,
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// but the corresponding theory relation and it's variable
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// are already more concrete.
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(None, None)
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member private r.makeBoundsMA (bv:Var, newExpl:Literal, newBounds:Interval)
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(bounds:Ref<BoundsValuation>)
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(db:Ref<Database>)
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(stats:Ref<Statistics>) =
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assert(newExpl <> 0) // CMW: newExpl is the reason for whatever changed in the bounds;
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// could be lower, could be upper, could be both.
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if newBounds.isEmpty then
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(None, Some (ref (newClauseFromList [Negate newExpl])))
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else
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let newLB, newUB = newBounds.Lower, newBounds.Upper
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let oldBnds = (!bounds).get bv
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// CMW: New bounds are usually tighter than the old ones
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let lower_tighter = (BitVector.bvULT oldBnds.Lower newLB)
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let upper_tighter = (BitVector.bvULT newUB oldBnds.Upper)
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let rel = (!(!db).Theory).getThRelation (lit2var newExpl)
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assert(not (lower_tighter && upper_tighter) || rel.isPAPredicate)
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if lower_tighter || upper_tighter then
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let nL = if lower_tighter then newLB else oldBnds.Lower
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let nU = if upper_tighter then newUB else oldBnds.Upper
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let oldLExpl = (!bounds).L_explanation.[bv]
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let oldUExpl = (!bounds).U_explanation.[bv]
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if BitVector.bvUGT nL nU then
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//xTheory conflict
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let mutable cls = []
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for l in [ oldLExpl; oldUExpl; newExpl ] do
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let already_in_cls = (List.exists (fun x -> x = (Negate l)) cls)
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if l <> 0 && not already_in_cls then
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cls <- (Negate l) :: cls
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let cc = newClauseFromList cls
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assert(not (clauseContainsDuplicates cc))
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(None, Some (ref cc))
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else
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// These explanations have to be updated here, otherwise the conflict resolution
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// for the conflict in the previous case will be wrong.
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if lower_tighter then (!bounds).L_explanation.[bv] <- newExpl
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if upper_tighter then (!bounds).U_explanation.[bv] <- newExpl
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let newBnds = Interval(nL, nU)
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(!bounds).set bv (newBnds)
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bumpOrder db bv
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(!stats).ModelAssignment()
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trace <| (lazy sprintf " | ==> %d:bv is in %s (because of %d)" bv (newBnds.ToString()) newExpl)
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(Some (BAssgnmnt (bv, (oldLExpl, oldUExpl), oldBnds)), None)
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else
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// CMW: This can happen, e.g., when we see a new constraint that has weaker bounds
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// than an old one. There's a chance that we run into non-termination issues
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// if we ignore them here (could erroneously learn weak bounds forever).
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(None, None)
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member private r.pushMA (l:Literal)
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(bVal:Ref<BooleanValuation>)
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(bvVal:Ref<BitVectorValuation>)
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(bounds:Ref<BoundsValuation>)
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(db:Ref<Database>)
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(stats:Ref<Statistics>) =
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let mutable cnflct = None
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if (!(!db).Theory).isDefined (lit2var l) then
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let rel = (!(!db).Theory).getThRelation (lit2var l)
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// CMW: in a more general framework we would iterate
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// over all theories here and ask each of them for "news".
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// For now, we have only the following two theories.
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// RLEBV Theory hook.
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if rel.isPAPredicate then
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let v = rel.getPAPredicateVariable
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let value = rel.getPAPredicateValue (!db).Numerals
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if isPositive(l) then
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// Positive PAPredicate
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let args = (v, rel.getBoolVar, value)
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let te = r.makeRLEMA args bvVal bounds db stats
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match te with
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| (Some(e),None) -> r.pushElement e
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| (None, Some cRef) -> cnflct <- Some cRef //xTheory conflict
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| _ -> ()
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else
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// Negative PAPredicate
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if not (value.isConcreteValue) then
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let oldValue = (!bvVal).getValue v
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let oldExpl = (!bvVal).getExplanation v
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let negPABool = Negate rel.getBoolVar
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let intersection = BitVector.Intersect oldValue value
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if intersection.isInvalid then
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assert (oldExpl <> Negate negPABool)
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let cls = collectLiterals([ negPABool;
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Negate oldExpl;
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])
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cnflct <- Some (ref (newClauseFromList cls))
|
|
|
|
elif USE_BOUNDS then
|
|
// let oldBnds = (!bounds).get v
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|
//
|
|
// if BitVector.bvULT intersection.Maximum oldBnds.Lower then
|
|
// let cls = collectLiterals([ negPABool;
|
|
// Negate (!bounds).L_explanation.[v];
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|
// Negate oldExpl;
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|
// ])
|
|
// cnflct <- Some (ref (newClauseFromList cls))
|
|
//
|
|
// elif cnflct = None && BitVector.bvULT oldBnds.Upper intersection.Minimum then
|
|
// let cls = collectLiterals([ negPABool;
|
|
// Negate (!bounds).U_explanation.[v];
|
|
// Negate oldExpl;
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|
// ])
|
|
// cnflct <- Some (ref (newClauseFromList cls))
|
|
// else
|
|
// //Now we can introduce extractions to block unwanted model assignment attempts.
|
|
()
|
|
else //value.isConcreteValue
|
|
|
|
if USE_BOUNDS then
|
|
|
|
// let oldBnds = ((!bounds).get v)
|
|
// let negPABool = rel.getBoolVar
|
|
//
|
|
//
|
|
// // This is a special cross-theory case where
|
|
// // a negatively asserted model assignment
|
|
// // can refine the bounds slightly.
|
|
//
|
|
// // Note: Previously we had reasons for the lower and upper bound, now we
|
|
// // refine one of them based on information from a PAPredicate. To make
|
|
// // this work correctly, we need to introduce a new _bounds_ predicate,
|
|
// // such that we have oldBnds /\ not PAPredicate => newBoundsPredicate.
|
|
//
|
|
// let (newBnds, newPred, oldExpl) =
|
|
// if (BitVector.bvEQ oldBnds.Lower value) then
|
|
// let newLower = BitVector.bvAdd oldBnds.Lower (BitVector.One oldBnds.Lower.Length)
|
|
// (Interval(newLower, oldBnds.Upper),
|
|
// (getLowerBoundPredicate db v newLower bVal bvVal bounds),
|
|
// (!bounds).L_explanation.[v])
|
|
// elif (BitVector.bvEQ oldBnds.Upper value) then
|
|
// let newUpper = BitVector.bvSub oldBnds.Upper (BitVector.One oldBnds.Upper.Length)
|
|
// (Interval(oldBnds.Lower, newUpper),
|
|
// (getUpperBoundPredicate db v newUpper bVal bvVal bounds),
|
|
// (!bounds).U_explanation.[v])
|
|
// else
|
|
// (oldBnds, TheoryRelation.EmptyThRel, 0)
|
|
//
|
|
// let newBool = newPred.getBoolVar
|
|
// let newBoolVal = (!bVal).getValueB newBool
|
|
//
|
|
// if newBnds.isEmpty then
|
|
// let cls = collectLiterals([ negPABool;
|
|
// Negate (!bounds).L_explanation.[v];
|
|
// Negate (!bounds).U_explanation.[v] ])
|
|
// cnflct <- Some (ref (newClauseFromList cls))
|
|
// elif newBoolVal = False then
|
|
// let cls = collectLiterals([ negPABool;
|
|
// Negate (!bounds).L_explanation.[v];
|
|
// Negate (!bounds).U_explanation.[v];
|
|
// newBool ])
|
|
// cnflct <- Some (ref (newClauseFromList cls))
|
|
// elif newBoolVal = Undefined && oldBnds <> newBnds then
|
|
// // CMW: collectLiterals reverses the order of the literals;
|
|
// // we have to make sure that `newBool' is first.
|
|
// let cls = collectLiterals [ Negate oldExpl; negPABool; newBool ]
|
|
// let ic = newClauseFromList cls
|
|
// cnflct <- r.Push bVal bvVal bounds db stats (Imp (ref ic, newBool))
|
|
// else
|
|
// // We can learn that: not (x = a) => x < a \/ x >a
|
|
// // which is equivalent to x=a \/ not x<=a \/ not x>=a
|
|
//// let x_leq_value = getUpperBoundPredicate db v value bVal pAss bounds
|
|
//// let value_leq_x = getLowerBoundPredicate db v value bVal pAss bounds
|
|
//// let gt = Negate (x_leq_value.getBoolVar)
|
|
//// let lt = Negate (value_leq_x.getBoolVar)
|
|
//// let implication = [rel.getBoolVar; gt; lt ]
|
|
//// let c = newClauseFromList implication
|
|
////
|
|
//// let gtVal = (!bVal).getValueB gt
|
|
//// let ltVal = (!bVal).getValueB lt
|
|
//// assert ( (!bVal).getValueB (rel.getBoolVar) = False)
|
|
//// assert ( gtVal = Undefined || ltVal = Undefined)
|
|
////
|
|
//// if not ((!(!db).Clauses).isStored c) then
|
|
//// let status = (!db).addAndWatchClause bVal c
|
|
////
|
|
//// match status with
|
|
//// | Clause.Unsat -> assert(false)
|
|
//// | Clause.Implication ->
|
|
//// assert ( (!bVal).getValueB c.[1] = Undefined)
|
|
//// cnflct <- r.Push bVal pAss bounds db stats (Imp (ref c, c.[1], None))
|
|
//// | _ -> ()
|
|
// ()
|
|
()
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
if USE_BOUNDS then
|
|
// Bounds theory hook.
|
|
|
|
if rel.isBoundsPredicate && (not rel.isPAPredicate || isPositive l) then //AZ: This is to avoid duplicate propagation of x =/= cnst,
|
|
// since it is already handled above.
|
|
let v = rel.getBoundsPredicateVariable
|
|
let newBnds = rel.getBoundsPredicateValue (!db).Numerals
|
|
|
|
|
|
let args = if isPositive l then (v, l, newBnds)
|
|
else (v, l, newBnds.Complement())
|
|
|
|
//if isPositive(l) then
|
|
// Positive BoundsPredicate
|
|
//let args = (v, rel.getBoolVar, newBnds)
|
|
let te = r.makeBoundsMA args bounds db stats
|
|
match te with
|
|
| (Some(e), None) -> r.pushElement e
|
|
| (None,Some cRef) -> cnflct <- Some cRef //xTheory conflict
|
|
| (Some _, Some _) -> UNREACHABLE "Propagation in a conflict state"
|
|
| _ -> ()
|
|
|
|
let bnds = ((!bounds).get v)
|
|
if cnflct.IsNone && (fst te).IsSome && bnds.isSingleton then
|
|
let oldValue = (!bvVal).getValue v
|
|
let newValue = bnds.Lower
|
|
|
|
if BitVector.bvEQ oldValue newValue then
|
|
()
|
|
else
|
|
// Note: This is a new RLE theory assignment with bounds theory reasons,
|
|
// i.e., this is a cross-theory implication. This could create trouble
|
|
// later, if we assume all reasons are exclusively bounds reasons, or
|
|
// exclusively MA reasons.
|
|
|
|
let newPred = getModelAssignmentPredicate db v newValue bVal bvVal bounds
|
|
|
|
let newBool = newPred.getBoolVar
|
|
let (lExpl,uExpl) = (!bounds).getExplanations v
|
|
|
|
// CMW: collectLiterals reverses the order of the literals;
|
|
// we have to make sure that `newBool' is first.
|
|
let explanation = newClauseFromList (collectLiterals([ Negate lExpl; Negate uExpl; newBool ]))
|
|
|
|
match (!bVal).getValueB newBool with
|
|
| True -> assert(false) // AZ: Deriving old knowledge should not be possible here
|
|
| False -> cnflct <- Some (ref explanation) //xTheory conflict
|
|
| Undefined -> //xTheory propagation
|
|
cnflct <- r.Push bVal bvVal bounds db stats (Imp (ref explanation, newBool))
|
|
()
|
|
()
|
|
// else
|
|
// // Negative BoundsPredicate
|
|
//
|
|
// // CMW: Todo. We should be able to use negative bounds information too,
|
|
// // but I'm not sure whether we absolutely have to catch this case to
|
|
// // get enough information for decisions/conflict resolution not to fail.
|
|
// ()
|
|
|
|
|
|
|
|
cnflct |