Make findLoops able to look for at most one loop

comSubExp expects exactly one loop to be found, so we do not look for
all 12798 loops if we know the result will be discarded. Slightly
helps ticket:4798.

Belonging to [master]:
  - #1945

Author: sjoelund

Compiler/BackEnd/CommonSubExpression.mo

@@ -2179,7 +2179,7 @@ algorithm
     equation
           //print("partition "+stringDelimitList(List.map(partition, intString), ", ")+"\n");
       // partition has only one loop
-      ({loop1}, _, _) = ResolveLoops.resolveLoops_findLoops({partition}, m, mT);
+      ({loop1}, _, _) = ResolveLoops.resolveLoops_findLoops({partition}, m, mT, findExactlyOneLoop=true);
           //print("loop1 "+stringDelimitList(List.map(loop1, intString), ", ")+"\n");
       {eqIdx1, eqIdx2} = loop1;
       varIdcs1 = arrayGet(m, eqIdx1);

Compiler/BackEnd/ResolveLoops.mo

@@ -362,6 +362,7 @@ public function resolveLoops_findLoops "author:Waurich TUD 2014-02
   input list<list<Integer>> partitionsIn;
   input BackendDAE.IncidenceMatrix mIn;  // the whole system of simpleEquations
   input BackendDAE.IncidenceMatrixT mTIn;
+  input Boolean findExactlyOneLoop=false;
   output list<list<Integer>> loopsOut = {};
   output list<Integer> crossEqsOut = {};
   output list<Integer> crossVarsOut = {};
@@ -383,7 +384,10 @@ algorithm
       varCrossLst := List.fold2(partitionVars,gatherCrossNodes,mTIn,mIn,{});
 
       // search the partitions for loops
-      loops := resolveLoops_findLoops2(partition,eqCrossLst,varCrossLst,mIn,mTIn);
+      loops := resolveLoops_findLoops2(partition,eqCrossLst,varCrossLst,mIn,mTIn,findExactlyOneLoop);
+      if if findExactlyOneLoop then (not listEmpty(loops) and not listEmpty(loopsOut)) else false then
+        fail();
+      end if;
       loopsOut := listAppend(loops,loopsOut);
       if isPresent(crossEqsOut) then
         crossEqsOut := listAppend(eqCrossLst,crossEqsOut);
@@ -404,6 +408,7 @@ protected function resolveLoops_findLoops2 "author: Waurich TUD 2014-01
   input list<Integer> varCrossLstIn;
   input BackendDAE.IncidenceMatrix mIn;  // the whole system of simpleEquations
   input BackendDAE.IncidenceMatrixT mTIn;
+  input Boolean findExactlyOneLoop;
   output list<list<Integer>> loopsOut;
 algorithm
   loopsOut := match(eqsIn,eqCrossLstIn,varCrossLstIn,mIn,mTIn)
@@ -439,6 +444,11 @@ algorithm
         simpleLoops = if isNoSingleLoop then simpleLoops else {subLoop};
         paths0 = listAppend(simpleLoops,connectedPaths);
         paths0 = sortPathsAsChain(paths0);
+        if findExactlyOneLoop then
+          if not listEmpty(paths0) then
+            {_} = paths0;
+          end if;
+        end if;
 
         //print("all paths to be resolved: \n"+stringDelimitList(List.map(paths0,HpcOmTaskGraph.intLstString)," / ")+"\n");
       then
@@ -461,8 +471,12 @@ algorithm
         closedPaths = List.map(closedPaths,List.unique);
         closedPaths = List.map1(closedPaths,getEqNodesForVarLoop,mTIn);// get the eqs for these varLoops
           //print("solve the smallest loops: \n"+stringDelimitList(List.map(closedPaths,HpcOmTaskGraph.intLstString)," / ")+"\n");
-       then
-        closedPaths;
+        if findExactlyOneLoop then
+          if not listEmpty(closedPaths) then
+            {_} = closedPaths;
+          end if;
+        end if;
+      then closedPaths;
     case(_,{},{},_,_)
       algorithm
         // no crossNodes
@@ -474,8 +488,7 @@ algorithm
             break;
           end if;
         end for;
-       then
-         {subLoop};
+      then {subLoop};
     case(_,_::_,_::_,_,_)
       algorithm
         //print("there are both varCrossNodes and eqNodes\n");
@@ -487,11 +500,10 @@ algorithm
           arrayUpdate(mTIn, i, List.sort(mTIn[i], intGt));
         end for;
         eqCrossSet := AvlSetInt.addList(AvlSetInt.EMPTY(), eqCrossLstIn);
-        paths := getShortPathsBetweenEqCrossNodes(AvlSetInt.listKeysReverse(eqCrossSet), eqCrossSet, mIn, mTIn, {});
+        paths := getShortPathsBetweenEqCrossNodes(AvlSetInt.listKeysReverse(eqCrossSet), eqCrossSet, mIn, mTIn, {}, findExactlyOneLoop);
         //
          //print("GOT SOME NEW LOOPS: \n"+stringDelimitList(List.map(paths,HpcOmTaskGraph.intLstString)," / ")+"\n");
-      then
-        paths;
+      then paths;
     else
       equation
         Error.addInternalError("function resolveLoops_findLoops2 failed", sourceInfo());
@@ -546,6 +558,7 @@ author: vwaurich TUD 12-2016"
   input BackendDAE.IncidenceMatrix mIn;
   input BackendDAE.IncidenceMatrixT mTIn;
   input list<list<Integer>> pathsIn;
+  input Boolean findExactlyOneLoop;
   output list<list<Integer>> pathsOut;
 algorithm
   pathsOut := match(eqCrossLstIn, mIn, mTIn, pathsIn)
@@ -567,12 +580,16 @@ algorithm
           //print("all sharedVars "+stringDelimitList(List.map(sharedVars, intString),",")+"\n");
           if hasSameIntSortedExcept(adjVars, arrayGet(mIn, adjEq), adjVar) then
             newPath := adjEq::{crossEq};
+            // TODO: List.unionElt is slow
             paths := List.unionElt(newPath, paths);
             //print("found path "+stringDelimitList(List.map(newPath,intString)," ; ")+"\n");
+            if if findExactlyOneLoop then (not listEmpty(pathsIn)) else false then
+              fail();
+            end if;
           end if;
         end for;
       end for;
-      paths := getShortPathsBetweenEqCrossNodes(rest, eqCrossSet, mIn, mTIn, listAppend(paths, pathsIn));
+      paths := getShortPathsBetweenEqCrossNodes(rest, eqCrossSet, mIn, mTIn, listAppend(paths, pathsIn), findExactlyOneLoop);
     then paths;
   case({},_,_,_)
     then pathsIn;