[BE] improve inverse algorithm handling

 - attempt to fix ticket:4855

Belonging to [master]:
  - OpenModelica/OMCompiler#2336
  - OpenModelica/OpenModelica-testsuite#913

Compiler/BackEnd/BackendDAEOptimize.mo

@@ -3700,7 +3700,7 @@ algorithm
   end match;
 end eaddInitialStmtsToAlgorithms1Helper;
 
-protected function expandAlgorithmStmts "Helper function to eaddInitialStmtsToAlgorithms1Helper."
+public function expandAlgorithmStmts "Helper function to eaddInitialStmtsToAlgorithms1Helper."
   input list<DAE.Statement> inAlg;
   input list<DAE.Exp> inOutputs;
   input BackendDAE.Variables inVars;

Compiler/SimCode/SimCode.mo

@@ -340,10 +340,10 @@ uniontype SimEqSystem
   end SES_ALGORITHM;
 
   record SES_INVERSE_ALGORITHM
-    "this should only occur inside SES_NONLINEAR"
     Integer index;
     list<DAE.Statement> statements;
     list<DAE.ComponentRef> knownOutputCrefs "this is a subset of output crefs of the original algorithm, which are already known";
+    Boolean insideNonLinearSystem;
     BackendDAE.EquationAttributes eqAttr;
   end SES_INVERSE_ALGORITHM;
 

Compiler/SimCode/SimCodeUtil.mo

@@ -5546,6 +5546,8 @@ algorithm
       DAE.ElementSource source;
       DAE.Expand crefExpand;
       BackendDAE.EquationAttributes eqAttr;
+      list<SimCode.SimEqSystem> result;
+      list<DAE.Exp> discreteVarsExp;
       constant Boolean debug = false;
 
     // normal call
@@ -5580,6 +5582,7 @@ algorithm
       // get and expand the searched variables
       solvedVars = List.map(vars, BackendVariable.varCref);
       solvedVars = List.unionList(List.map1(solvedVars, ComponentReference.expandCref, true));
+      if debug then BackendDump.debugStrCrefLstStr("solvedVars : ", solvedVars, ", ", "\n"); end if;
 
       // get and expand all other variables
       algOutVars = CheckModel.checkAndGetAlgorithmOutputs(alg, source, crefExpand);
@@ -5588,10 +5591,14 @@ algorithm
       // the remaining quantity of all out vars to the solved vars
       knownOutputCrefs = List.setDifference(algOutVars, solvedVars);
 
-      //Why do we need to filter the discrete variables?
-      //List.filterOnTrue(BackendVariable.varList(knVars),BackendVariable.isRecordVar);
+      // filter since are not solvable with non-linear solver
       solvedVars = List.map(List.filterOnTrue(vars, BackendVariable.isVarNonDiscrete), BackendVariable.varCref);
 
+      // discrete vars are added with there start value and by
+      // event iteration we ensure that all variable are consistent
+      discreteVarsExp = list(Expression.crefToExp(BackendVariable.varCref(v)) for v in List.filterOnTrue(vars, BackendVariable.isVarDiscrete));
+      algStatements = BackendDAEOptimize.expandAlgorithmStmts(algStatements, discreteVarsExp, BackendVariable.listVar(vars), true);
+
       if debug then
         BackendDump.debugStrCrefLstStr("algOutVars : ", algOutVars, ", ", "\n");
         BackendDump.debugStrCrefLstStr("filtered solvedVars: ", solvedVars, ", ", "\n");
@@ -5601,8 +5608,20 @@ algorithm
       //Why should we have the same amount of solved vars and know vars?
       //true = intEq(listLength(solvedVars), listLength(knownOutputCrefs));
 
+      alg = DAE.ALGORITHM_STMTS(algStatements);
       DAE.ALGORITHM_STMTS(algStatements) = BackendDAEUtil.collateAlgorithm(alg, NONE());
-    then ({SimCode.SES_NONLINEAR(SimCode.NONLINEARSYSTEM(iuniqueEqIndex+1, {SimCode.SES_INVERSE_ALGORITHM(iuniqueEqIndex, algStatements, knownOutputCrefs, eqAttr)}, solvedVars, 0, listLength(vars), NONE(), false, false, false), NONE(), eqAttr)}, iuniqueEqIndex+2);
+
+      if not listEmpty(solvedVars) then
+        result = {SimCode.SES_NONLINEAR(SimCode.NONLINEARSYSTEM(iuniqueEqIndex+1,
+                      {SimCode.SES_INVERSE_ALGORITHM(iuniqueEqIndex, algStatements, knownOutputCrefs, true, eqAttr)},
+                   solvedVars, 0, listLength(vars), NONE(), false, false, false), NONE(), eqAttr)};
+        ouniqueEqIndex = iuniqueEqIndex+2;
+      else
+        result = {SimCode.SES_INVERSE_ALGORITHM(iuniqueEqIndex, algStatements, knownOutputCrefs, false, eqAttr)};
+        ouniqueEqIndex = iuniqueEqIndex+1;
+      end if;
+
+    then (result, ouniqueEqIndex);
 
     // Error message, inverse algorithms cannot be solved for discrete variables
     case (BackendDAE.ALGORITHM(alg=alg, source=source, expand=crefExpand, attr=eqAttr)::_, _) equation
@@ -11752,7 +11771,7 @@ author:Waurich TUD 2014-05"
 algorithm
     simEqSysOut := match(simEqSysIn,idx)
     local
-      Boolean pom,changed,ic;
+      Boolean pom,changed,ic, inls;
       Integer idxLS,idxNLS,idxMX,nUnknowns;
       list<Boolean> bLst;
       DAE.ComponentRef cref;
@@ -11797,8 +11816,8 @@ algorithm
     case(SimCode.SES_ALGORITHM(statements=stmts,eqAttr=eqAttr), _) equation
       simEqSys = SimCode.SES_ALGORITHM(idx,stmts, eqAttr);
     then simEqSys;
-    case(SimCode.SES_INVERSE_ALGORITHM(statements=stmts, knownOutputCrefs=crefs,eqAttr=eqAttr), _) equation
-      simEqSys = SimCode.SES_INVERSE_ALGORITHM(idx, stmts, crefs, eqAttr);
+    case(SimCode.SES_INVERSE_ALGORITHM(statements=stmts, knownOutputCrefs=crefs,insideNonLinearSystem=inls,eqAttr=eqAttr), _) equation
+      simEqSys = SimCode.SES_INVERSE_ALGORITHM(idx, stmts, crefs, inls, eqAttr);
     then simEqSys;
     case(SimCode.SES_LINEAR(SimCode.LINEARSYSTEM(partOfMixed=pom,tornSystem=tornSystem,vars=simVars,beqs=expLst,sources=sources,simJac=simJac,residual=simEqSysLst,jacobianMatrix=jac,indexLinearSystem=idxLS,nUnknowns=nUnknowns),eqAttr=eqAttr),_)
       equation

Compiler/Template/CodegenC.tpl

@@ -4855,7 +4855,6 @@ template equation_arrayFormat(SimEqSystem eq, String name, Context context, Inte
   case e as SES_IFEQUATION(__)
     then equationIfEquationAssign(e, context, &varD, &tempeqns, modelNamePrefix)
   case e as SES_ALGORITHM(__)
-    then equationAlgorithm(e, context, &varD, &tempeqns)
   case e as SES_INVERSE_ALGORITHM(__)
     then equationAlgorithm(e, context, &varD, &tempeqns)
   case e as SES_LINEAR(__)
@@ -4956,9 +4955,8 @@ template equation_impl2(Integer clockIndex, SimEqSystem eq, Context context, Str
     then equationArrayCallAssign(e, context, &varD, &tempeqns)
   case e as SES_IFEQUATION(__)
     then equationIfEquationAssign(e, context, &varD, &tempeqns, modelNamePrefix)
-  case e as SES_ALGORITHM(__)
-    then equationAlgorithm(e, context, &varD, &tempeqns)
   case e as SES_INVERSE_ALGORITHM(__)
+  case e as SES_ALGORITHM(__)
     then equationAlgorithm(e, context, &varD, &tempeqns)
   case e as SES_LINEAR(__)
     then equationLinear(e, context, &varD)
@@ -5211,11 +5209,32 @@ template equationAlgorithm(SimEqSystem eq, Context context, Text &varDecls, Text
  "Generates an equation that is an algorithm."
 ::=
 match eq
-case SES_ALGORITHM(__)
-case SES_INVERSE_ALGORITHM(__) then
+/* SES_INVERSE_ALGORITHM which is used by the non-linear solver */
+case alg as SES_INVERSE_ALGORITHM(insideNonLinearSystem=true)
+case SES_ALGORITHM(__) then
   (statements |> stmt =>
     algStatement(stmt, context, &varDecls, &auxFunction)
   ;separator="\n")
+/* Generates an equation that is an inverse algorithm
+  without continuous variables, discrete variables are
+  handled by the event iteration */
+case alg as SES_INVERSE_ALGORITHM(__) then
+  let backupKnown = (alg.knownOutputCrefs |> cr hasindex i0 =>
+    let &varDecls += '<%crefType(cr)%> OLD_<%i0%>;<%\n%>'
+       'OLD_<%i0%> = <%cref(cr)%>;'
+      ;separator="\n")
+  let stmts = (statements |> stmt =>
+    algStatement(stmt, context, &varDecls, &auxFunction)
+  ;separator="\n")
+  let restoreKnownVars = (alg.knownOutputCrefs |> cr hasindex i0 => '<%cref(cr)%> = OLD_<%i0%>;' ;separator="\n")
+  <<
+  /* backup outputs of the algorithm */
+  <%backupKnown%>
+  /* algrithm it self */
+  <%stmts%>
+  /* restore outputs of the algorithm */
+  <%restoreKnownVars%>
+  >>
 end equationAlgorithm;
 
 template equationLinear(SimEqSystem eq, Context context, Text &varDecls)

Compiler/Template/SimCodeTV.mo

@@ -464,10 +464,10 @@ package SimCode
     end SES_ALGORITHM;
 
     record SES_INVERSE_ALGORITHM
-      "this should only occur inside SES_NONLINEAR"
       Integer index;
       list<DAE.Statement> statements;
       list<DAE.ComponentRef> knownOutputCrefs "this is a subset of output crefs of the original algorithm, which are already known";
+      Boolean insideNonLinearSystem;
       BackendDAE.EquationAttributes eqAttr;
     end SES_INVERSE_ALGORITHM;