Multi-obj: refactor solve iteration loop #239

PrepareNextIter() gets lambdas to obtain solution status and solution

Author: glebbelov

include/mp/backend-std.h

@@ -268,11 +268,16 @@ class StdBackend :
 
   /// Our solving procedure.
   virtual void RunSolveIterations() {
-    while (GetMM().PrepareSolveIteration()) {
+    auto get_stt = [this]() {          // to be called before GetSolution()
+      auto sr = GetSolveResult();
+      SetStatus( sr );
+      return (sol::Status)sr.first;
+    };
+    auto get_sol = [this]() {
+      return GetSolution();
+    };
+    while (GetMM().PrepareSolveIteration(get_stt, get_sol)) {
       Solve();
-      SetStatus( GetSolveResult() );      // before GetSolution()
-      sol_last_ = GetSolution();          // @todo don't need it in the last iteration
-      GetMM().ProcessIterationSolution(sol_last_, status_.first);
     }
   }
 
@@ -656,7 +661,6 @@ class StdBackend :
   std::pair<int, std::string> status_ { sol::NOT_SET, "status not set" };
   int kIntermSol_ = 0;   // last written intermed solution index
   std::pair<double, double> objIntermSol_ { -1e100, 1e100 };
-  Solution sol_last_;
 
   ///////////////////////// STORING SOLVER MESSAGES //////////////////////
 private:

include/mp/converter-base.h

@@ -33,10 +33,9 @@ class BasicConverter : public EnvKeeper {
   virtual void ConvertModel() = 0;
 
   /// Need and successfully prepared the next solve iteration?
-  virtual bool PrepareSolveIteration() = 0;
-
-  /// Process solve iteration solution
-  virtual void ProcessIterationSolution(const Solution& , int status) = 0;
+  virtual bool PrepareSolveIteration(
+      std::function<sol::Status(void)> get_stt, std::function<Solution(void)> get_sol)
+      = 0;
 
   /// Objective weights
   virtual ArrayRef<double> GetObjWeightsAdapted() = 0;

include/mp/flat/converter.h

@@ -231,19 +231,14 @@ class FlatConverter :
   /// This should be used in particular with MO emulation.
   /// @return true if the next solve should be executed
   /// and its results passed via ProcessSolveIterationSolution().
-  bool PrepareNextSolveIteration() {
+  bool PrepareNextSolveIteration(
+      std::function<sol::Status(void)> get_stt, std::function<Solution(void)> get_sol) {
     if (MPCD( IsMOActive() ))
-      return MPD( PrepareMOIteration() );
+      return MPD( PrepareMOIteration(get_stt, get_sol) );
     return !(n_solve_iter_++);
   }
 
-  /// Process solve iteration solution.
-  void ProcessSolveIterationSolution(const Solution& sol, int status) {
-    if (MPCD( IsMOActive() ))
-      MPD( ProcessMOIterationPostsolvedSolution(sol, status) );
-  }
-
-  /// Objective weights
+  /// Objective weights, adapted according to obj:multi:weight
   ArrayRef<double> GetObjWeightsAdapted() { return MPD( GetMOWeightsLegacy() ); }
 
 

include/mp/flat/converter_multiobj.h

@@ -49,22 +49,45 @@ class MOManager {
   /// Prepare next multiobj iteration?
   /// @note Call this before a MO iteration.
   /// @return true iff the model is ready for the next iteration.
-  bool PrepareMOIteration() {
+  bool PrepareMOIteration(
+      std::function<sol::Status(void)> get_stt, std::function<Solution(void)> get_sol) {
     switch (status_) {
     case MOManagerStatus::NOT_SET:
-      MP_RAISE("FlatConverter: MultiobjManager not started");
+      MP_RAISE("FlatConverter: MultiobjManager not set up");
     case MOManagerStatus::NOT_ACTIVE:
       MP_RAISE("FlatConverter: MultiobjManager not running");
     case MOManagerStatus::RUNNING:
-      return DoPrepareNextMultiobjSolve();
+      return DoPrepareNextMultiobjSolve(get_stt, get_sol);
     case MOManagerStatus::FINISHED:
       return false;
     }
     return false;
   }
 
+  /// Obtain and process a postsolved solution of the current iteration.
+  /// Can implicitly call ProcessMOIterationUnpostsolvedSolution().
+  /// @return (whether we should continue, solve_result).
+  std::pair<bool, sol::Status> ProcessMOIterationPostsolvedSolution(
+      std::function<sol::Status(void)> get_stt, std::function<Solution(void)> get_sol) {
+    auto solst = get_stt();
+    assert(sol::Status::NOT_SET != solst);
+    assert(IsMOActive());
+    assert(MOManagerStatus::FINISHED != status_);
+    if ((sol::IsProblemSolvedOrFeasible((sol::Status)solst)
+        // || sol::IsProblemMaybeSolved(solst)    // Use this?
+         )  && !sol::IsProblemUnbounded((sol::Status)solst)  // Don't want unbounded
+        ) {                                                  // (but LIMIT can have this undiscovered)
+      get_sol();    // This implicitly calls ProcessMOIterationUnpostsolvedSolution().
+      return { true, solst };
+      // We ignore the solution here - but having it provided
+      // guarantees that the postsolve has been run.
+    }
+    status_ = MOManagerStatus::FINISHED;
+    return { false, solst };
+  }
+
   /// Process an unpostsolved solution of the current iteration.
-  /// Necessary to be called.
+  /// This is called from solution postsolve initiated by solution getter.
   /// @note Can be called before or after the postsolved solution.
   void ProcessMOIterationUnpostsolvedSolution(pre::ModelValuesDbl& sol) {
     if (IsMOActive()) {
@@ -79,24 +102,6 @@ class MOManager {
     }
   }
 
-  /// Process a postsolved solution of the current iteration.
-  /// Necessary to be called.
-  /// @note Can be called before or after unpostsolved solution.
-  /// Should contain at least valid solve status.
-  void ProcessMOIterationPostsolvedSolution(const Solution& , int solst) {
-    assert(sol::Status::NOT_SET != solst);
-    assert(IsMOActive());
-    assert(MOManagerStatus::FINISHED != status_);
-    if ((sol::IsProblemSolvedOrFeasible((sol::Status)solst)
-        // || sol::IsProblemMaybeSolved(solst)    // Use this?
-         ) && !sol::IsProblemUnbounded((sol::Status)solst))
-    {}  // continue
-    else
-      status_ = MOManagerStatus::FINISHED;
-    // We ignore the solution here - but having it provided
-    // guarantees that the postsolve has been run.
-  }
-
 
 protected:
   void SetupMultiobjEmulation() {
@@ -161,7 +166,8 @@ class MOManager {
   }
 
   /// Do prepare next solve
-  bool DoPrepareNextMultiobjSolve() {
+  bool DoPrepareNextMultiobjSolve(
+      std::function<sol::Status(void)> get_stt, std::function<Solution(void)> get_sol) {
     if (++i_current_obj_ >= obj_new_.size()) {
       status_ = MOManagerStatus::FINISHED;
       MPD( GetEnv() ).Print(
@@ -176,8 +182,20 @@ class MOManager {
           "MULTI-OBJECTIVE MODE: objective {} (out of {}) ...\n"
           "==============================================================================\n\n"
           , i_current_obj_+1, obj_new_.size());
-    if (i_current_obj_)
+    if (i_current_obj_) {
+      auto proc_sol = ProcessMOIterationPostsolvedSolution(get_stt, get_sol);
+      if (!proc_sol.first) {
+        if (MPD( GetEnv() ).verbose_mode())
+          MPD( GetEnv() ).Print(
+              "\n"
+              "MULTI-OBJECTIVE MODE: objective {} (out of {}):\n"
+              "    ABORTING due to the previous iteration's solve result ({}).\n"
+              "==============================================================================\n\n"
+              , i_current_obj_+1, obj_new_.size(), proc_sol.second);
+        return false;
+      }
       RestrictLastObjVal();
+    }
     MPD( FillConstraintCounters( MPD( GetModelAPI() ), *MPD( GetModelInfoWrt() ) ) );   // @todo a hack.
     MPD( GetModelAPI() ).InitProblemModificationPhase(   // For adding the new constraint. @todo a hack.
         MPD( GetModelInfo() ));                          // Ideally Model would notice changes and notify

include/mp/flat/problem_flattener.h

@@ -127,12 +127,10 @@ class ProblemFlattener :
   }
 
   /// Need and successfully prepared the next solve iteration?
-  bool PrepareSolveIteration() override
-  { return GetFlatCvt().PrepareNextSolveIteration(); }
-
-  /// Process solve iteration solution
-  void ProcessIterationSolution(const Solution& sol, int status) override
-  { GetFlatCvt().ProcessSolveIterationSolution(sol, status); }
+  bool PrepareSolveIteration(
+      std::function<sol::Status(void)> get_stt, std::function<Solution(void)> get_sol)
+      override
+  { return GetFlatCvt().PrepareNextSolveIteration(get_stt, get_sol); }
 
   /// Objective weights
   ArrayRef<double> GetObjWeightsAdapted() override

include/mp/model-mgr-base.h

@@ -71,10 +71,11 @@ class BasicModelManager {
                               double) = 0;
 
   /// Need and successfully prepared the next solve iteration?
-  virtual bool PrepareSolveIteration() = 0;
-
-  /// Process solve iteration solution
-  virtual void ProcessIterationSolution(const Solution& , int status) = 0;
+  /// @param get_stt: solution status getter.
+  ///   If called, then before get_sol.
+  /// @param get_sol: solution getter (for postsolved solution.)
+  virtual bool PrepareSolveIteration(
+      std::function<sol::Status(void)> get_stt, std::function<Solution(void)> get_sol) = 0;
 
   /// Objective weights in the 'legacy' format of the obj:multi:weight option
   virtual ArrayRef<double> GetObjWeightsAdapted() = 0;

include/mp/model-mgr-with-pb.h

@@ -287,12 +287,10 @@ class ModelManagerWithProblemBuilder :
   }
 
   /// Need and successfully prepared the next solve iteration?
-  bool PrepareSolveIteration() override
-  { return GetCvt().PrepareSolveIteration(); }
-
-  /// Process solve iteration solution
-  void ProcessIterationSolution(const Solution& sol, int status) override
-  { GetCvt().ProcessIterationSolution(sol, status); }
+  bool PrepareSolveIteration(
+      std::function<sol::Status(void)> get_stt, std::function<Solution(void)> get_sol)
+      override
+  { return GetCvt().PrepareSolveIteration(get_stt, get_sol); }
 
   /// Objective weights
   ArrayRef<double> GetObjWeightsAdapted() override