Simplify the MISolver rounding interface (#6)

* Simplify the MISolver rounding type interface
* Remove the iterative method as it is a partial case of the multiple rounding
* Improve const-correctness
* Fix some comments
* Fix DEB_* statements

Solver/MISolver.cc

@@ -94,7 +94,7 @@ public:
 
   const ToRoundSetIter& get() const
   {
-    DEB_error_if(is_null(), "accessing an null iterator");
+    DEB_error_if(is_null(), "accessing null to-round iterator");
     return iter_;
   }
 
@@ -128,24 +128,19 @@ class MISolver::IterativeSolver : public IterativeSolverT<double>
 // Constructor
 MISolver::MISolver()
 {// default parameters
+  rounding_type_ = RoundingType::DEFAULT;
+
   initial_full_solution_ = true;
   iter_full_solution_ = true;
   final_full_solution_ = true;
 
-  direct_rounding_ = false;
-  no_rounding_ = false;
-  multiple_rounding_ = true;
-  gurobi_rounding_ = false;
-  cplex_rounding_ = false;
-
   max_local_iters_ = 100000;
   max_local_error_ = 1e-3;
   max_cg_iters_ = 50;
   max_cg_error_ = 1e-3;
 
   multiple_rounding_threshold_ = 0.5;
-
-  gurobi_max_time_ = 60;
+  max_time_ = 60;
 
   direct_solver_ = new DirectSolver;
   iter_solver_ = new IterativeSolver;
@@ -158,8 +153,7 @@ MISolver::~MISolver()
 }
 //-----------------------------------------------------------------------------
 
-void MISolver::solve(
-    CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round, bool _fixed_order)
+void MISolver::solve(CSCMatrix& _A, Vecd& _x, Vecd& _rhs, const Veci& _to_round)
 {
   DEB_enter_func;
   DEB_line(2, "integer variables #: " << _to_round.size());
@@ -169,27 +163,32 @@ void MISolver::solve(
   if (gmm::mat_ncols(_A) == 0 || gmm::mat_nrows(_A) == 0)
     return;
 
-  if (gurobi_rounding_)
-    solve_gurobi(_A, _x, _rhs, _to_round);
-  else if (cplex_rounding_)
-    solve_cplex(_A, _x, _rhs, _to_round);
-  else if (no_rounding_ || _to_round.size() == 0)
-    solve_no_rounding(_A, _x, _rhs);
-  else if (direct_rounding_)
-    solve_direct_rounding(_A, _x, _rhs, _to_round);
-  else if (multiple_rounding_)
-    solve_multiple_rounding(_A, _x, _rhs, _to_round);
-  else
-    solve_iterative(_A, _x, _rhs, _to_round, _fixed_order);
+  if (_to_round.empty())
+    return solve_no_rounding(_A, _x, _rhs);
+
+  switch (rounding_type_)
+  {
+  case RoundingType::NONE:
+    return solve_no_rounding(_A, _x, _rhs);
+  case RoundingType::DIRECT: 
+    return solve_direct_rounding(_A, _x, _rhs, _to_round);
+  case RoundingType::MULTIPLE: 
+    return solve_multiple_rounding(_A, _x, _rhs, _to_round);
+  case RoundingType::GUROBI:
+    return solve_gurobi(_A, _x, _rhs, _to_round);
+  case RoundingType::CPLEX:
+    return solve_cplex(_A, _x, _rhs, _to_round);
+  };
 }
 
 //-----------------------------------------------------------------------------
 
 // inline function...
-void MISolver::solve_cplex(CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round)
+void MISolver::solve_cplex(
+    CSCMatrix& _A, Vecd& _x, Vecd& _rhs, const Veci& _to_round)
 {
   DEB_enter_func;
-  DEB_out(2, "gurobi_max_time_: " << gurobi_max_time_ << "\n");
+  DEB_out(2, "gurobi_max_time_: " << max_time_ << "\n");
 
 #if COMISO_CPLEX_AVAILABLE
 
@@ -244,7 +243,7 @@ void MISolver::solve_cplex(CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round)
 
     // 4. solve
     IloCplex cplex(model);
-    cplex.setParam(IloCplex::TiLim, gurobi_max_time_);
+    cplex.setParam(IloCplex::TiLim, max_time_);
 
 #ifdef 0
     // set parameters comparable to CoMISo
@@ -277,7 +276,7 @@ void MISolver::solve_cplex(CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round)
   }
 
 #else
-  DEB_out(1, "CPLEX solver is not available, please install it...\n")
+  DEB_warning(1, "CPLEX solver is not available, please install it")
 #endif
 }
 
@@ -300,7 +299,7 @@ void MISolver::resolve(Vecd& _x, Vecd& _rhs)
 //-----------------------------------------------------------------------------
 
 void MISolver::solve_direct_rounding(
-    CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round)
+    CSCMatrix& _A, Vecd& _x, Vecd& _rhs, const Veci& _to_round)
 {
   DEB_enter_func;
   Veci to_round(_to_round);
@@ -432,150 +431,6 @@ void MISolver::solve_direct_rounding(
 
 //-----------------------------------------------------------------------------
 
-void MISolver::solve_iterative(
-    CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round, bool _fixed_order)
-{
-  DEB_enter_func;
-  // StopWatch
-  Base::StopWatch sw;
-  double time_search_next_integer = 0;
-
-  // some statistics
-  n_local_ = 0;
-  n_cg_ = 0;
-  n_full_ = 0;
-
-  // reset cholmod step flag
-  cholmod_step_done_ = false;
-
-  Veci to_round(_to_round);
-  // if the order is not fixed, uniquify the indices
-  if (!_fixed_order)
-  {
-    // copy to round vector and make it unique
-    std::sort(to_round.begin(), to_round.end());
-    Veci::iterator last_unique;
-    last_unique = std::unique(to_round.begin(), to_round.end());
-    size_t r = (size_t)(last_unique - to_round.begin());
-    to_round.resize(r);
-  }
-
-  // initalize old indices
-  Veci old_idx(_rhs.size());
-  for (unsigned int i = 0; i < old_idx.size(); ++i)
-    old_idx[i] = i;
-
-  if (initial_full_solution_)
-  {
-    DEB_line(2, "initial full solution");
-    direct_solver_->calc_system_gmm(_A);
-    direct_solver_->solve(_x, _rhs);
-
-    cholmod_step_done_ = true;
-
-    ++n_full_;
-  }
-
-  // neighbors for local optimization
-  Vecui neigh_i;
-
-  // Vector for reduced solution
-  Vecd xr(_x);
-
-  // loop until solution computed
-  for (unsigned int i = 0; i < to_round.size(); ++i)
-  {
-    DEB_line(11, "Integer DOF's left: " << to_round.size() - (i + 1) << " ");
-    DEB_line(11, "residuum_norm: " << COMISO_GMM::residuum_norm(_A, xr, _rhs));
-
-    // index to eliminate
-    unsigned int i_best = 0;
-
-    // position in round vector
-    unsigned int tr_best = 0;
-
-    if (_fixed_order) // if order is fixed, simply get next index from to_round
-    {
-      i_best = to_round[i];
-    }
-    else // else search for best rounding candidate
-    {
-      sw.start();
-      // find index yielding smallest rounding error
-      double r_best = FLT_MAX;
-      for (unsigned int j = 0; j < to_round.size(); ++j)
-      {
-        if (to_round[j] != -1)
-        {
-          int cur_idx = to_round[j];
-          const auto rnd_error = round_residue(xr[cur_idx]);
-          if (rnd_error < r_best)
-          {
-            i_best = cur_idx;
-            r_best = rnd_error;
-            tr_best = j;
-          }
-        }
-      }
-      time_search_next_integer += sw.stop();
-    }
-
-    // store rounded value
-    const auto rnd_x = double_round(xr[i_best]);
-    _x[old_idx[i_best]] = rnd_x;
-
-    // compute neighbors
-    neigh_i.clear();
-    Col col = gmm::mat_const_col(_A, i_best);
-    ColIter it = gmm::vect_const_begin(col);
-    ColIter ite = gmm::vect_const_end(col);
-    for (; it != ite; ++it)
-    {
-      if (it.index() != i_best)
-        neigh_i.push_back(static_cast<int>(it.index()));
-    }
-    // eliminate var
-    COMISO_GMM::fix_var_csc_symmetric(i_best, rnd_x, _A, xr, _rhs);
-    to_round[tr_best] = -1;
-
-    // 3-stage update of solution w.r.t. roundings
-    // local GS / CG / SparseCholesky
-    update_solution_is_local(_A, xr, _rhs, neigh_i);
-  }
-
-  // final full solution?
-  if (final_full_solution_)
-  {
-    DEB_line(2, "final full solution");
-
-    if (gmm::mat_ncols(_A) > 0)
-    {
-      if (cholmod_step_done_)
-        direct_solver_->update_system_gmm(_A);
-      else
-        direct_solver_->calc_system_gmm(_A);
-
-      direct_solver_->solve(xr, _rhs);
-      ++n_full_;
-    }
-  }
-
-  // store solution values to result vector
-  for (unsigned int i = 0; i < old_idx.size(); ++i)
-    _x[old_idx[i]] = xr[i];
-
-  // output statistics
-  DEB_line(2, " *** Statistics of MiSo Solver ***");
-  DEB_line(2, "Number of CG    iterations  = " << n_cg_);
-  DEB_line(2, "Number of LOCAL iterations  = " << n_local_);
-  DEB_line(2, "Number of FULL  iterations  = " << n_full_);
-  DEB_line(2, "Number of ROUNDING          = " << _to_round.size());
-  DEB_line(2, "time searching next integer = "
-                  << time_search_next_integer / 1000.0 << "s");
-}
-
-//-----------------------------------------------------------------------------
-
 bool MISolver::update_solution_is_local(
     const CSCMatrix& _A, Vecd& _x, const Vecd& _rhs, const Vecui& _neigh_i)
 {
@@ -671,7 +526,7 @@ void MISolver::solve_multiple_rounding(
   // use a doubly-indexed data structure to be able to access a "to_round"
   // variable by both its index and round residue
   ToRoundSet to_round; // variables yet to round sorted by round residue 
-  // pointer to the to_round variable in the residue array
+  // store iterators to the to_round variable in the residue sorted container
   std::vector<ToRoundSetIterExt> to_round_indx(_x.size());
 
   const auto add_to_round_index = 
@@ -762,7 +617,7 @@ void MISolver::solve_multiple_rounding(
 //-----------------------------------------------------------------------------
 
 void MISolver::solve_gurobi(
-    CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round)
+    CSCMatrix& _A, Vecd& _x, Vecd& _rhs, const Veci& _to_round)
 {
   DEB_enter_func;
 #if COMISO_GUROBI_AVAILABLE
@@ -779,7 +634,7 @@ void MISolver::solve_gurobi(
     GRBModel model = GRBModel(env);
 
     // set time limite
-    model.getEnv().set(GRB_DoubleParam_TimeLimit, gurobi_max_time_);
+    model.getEnv().set(GRB_DoubleParam_TimeLimit, max_time_);
 
     unsigned int n = _rhs.size();
 
@@ -843,13 +698,13 @@ void MISolver::solve_gurobi(
   }
 
 #else
-  DEB_out(1, "GUROBI solver is not available, please install it...\n");
+  DEB_warning(1, "GUROBI solver is not available, please install it");
 #endif
 }
 
 //----------------------------------------------------------------------------
 
-void MISolver::show_options_dialog()
+void MISolver::show_options_dialog() const
 {
   DEB_enter_func;
 #if (COMISO_QT4_AVAILABLE)

Solver/MISolver.hh

@@ -67,6 +67,18 @@ public:
   typedef std::vector<int> Veci;
   typedef std::vector<unsigned int> Vecui;
 
+  enum class RoundingType
+  {
+    NONE,     // no rounding at all, use with caution
+    DIRECT,   /* simple method that round all integer variables in one pass,
+                 fast, but solutions are far from optimal. */
+    MULTIPLE, /* greedy method that rounds several variables at once,
+                 controlled by set_multiple_rounding_threshold(). */
+    GUROBI,   // only available if you have the Gurobi solver configured
+    CPLEX,    // only available if you have the CPLEX solver configured
+    DEFAULT = MULTIPLE // default setting
+  };
+
   /// default Constructor
   MISolver();
 
@@ -88,8 +100,7 @@ public:
    *  @param _fixed_order specifies if _to_round indices shall be rounded in the
    *  given order (\b true) or be greedily selected (\b false)
    *  */
-  void solve(CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round,
-      bool _fixed_order = false);
+  void solve(CSCMatrix& _A, Vecd& _x, Vecd& _rhs, const Veci& _to_round);
 
   //! Resolve usig the direct solver
   void resolve(Vecd& _x, Vecd& _rhs);
@@ -106,7 +117,28 @@ public:
 
   /// show Qt-Options-Dialog for setting algorithm parameters
   /** Requires a Qt Application running and COMISO_GUI to be defined */
-  void show_options_dialog();
+  void show_options_dialog() const;
+
+  /// Set the solve type
+  void set_rounding_type(const RoundingType _rt) { rounding_type_ = _rt; }
+
+  /// Get the solve type
+  RoundingType get_rounding_type() const { return rounding_type_; }
+
+  /// Shall no rounding be performed?
+  void set_no_rounding() { rounding_type_ = RoundingType::NONE; }
+
+  /// Shall direct (or greedy) rounding be used?
+  void set_direct_rounding() { rounding_type_ = RoundingType::DIRECT; }
+
+  /// Shall multiple rounding be performed?
+  void set_multiple_rounding() { rounding_type_ = RoundingType::MULTIPLE; }
+
+  /// Shall Gurobi solver be used?
+  void set_gurobi_rounding() { rounding_type_ = RoundingType::GUROBI; }
+
+  /// Shall CPLEX solver be used?
+  void set_cplex_rounding() { rounding_type_ = RoundingType::CPLEX; }
 
   /** @name Get/Set functions for algorithm parameters
    * Besides being used by the Qt-Dialog these can also be called explicitly
@@ -115,42 +147,17 @@ public:
   /// Shall an initial full solution be computed?
   void set_inital_full(bool _b) { initial_full_solution_ = _b; }
   /// Will an initial full solution be computed?
-  bool get_inital_full() { return initial_full_solution_; }
+  bool get_inital_full() const { return initial_full_solution_; }
 
   /// Shall an full solution be computed if iterative methods did not converged?
   void set_iter_full(bool _b) { iter_full_solution_ = _b; }
   /// Will an full solution be computed if iterative methods did not converged?
-  bool get_iter_full() { return iter_full_solution_; }
+  bool get_iter_full() const { return iter_full_solution_; }
 
   /// Shall a final full solution be computed?
   void set_final_full(bool _b) { final_full_solution_ = _b; }
   /// Will a final full solution be computed?
-  bool get_final_full() { return final_full_solution_; }
-
-  /// Shall direct (or greedy) rounding be used?
-  void set_direct_rounding(bool _b) { direct_rounding_ = _b; }
-  /// Will direct rounding be used?
-  bool get_direct_rounding() { return direct_rounding_; }
-
-  /// Shall no rounding be performed?
-  void set_no_rounding(bool _b) { no_rounding_ = _b; }
-  /// Will no rounding be performed?
-  bool get_no_rounding() { return no_rounding_; }
-
-  /// Shall multiple rounding be performed?
-  void set_multiple_rounding(bool _b) { multiple_rounding_ = _b; }
-  /// Will multiple rounding be performed?
-  bool get_multiple_rounding() { return multiple_rounding_; }
-
-  /// Shall gurobi solver be used?
-  void set_gurobi_rounding(bool _b) { gurobi_rounding_ = _b; }
-  /// Will gurobi rounding be performed?
-  bool get_gurobi_rounding() { return gurobi_rounding_; }
-
-  /// Shall cplex solver be used?
-  void set_cplex_rounding(bool _b) { cplex_rounding_ = _b; }
-  /// Will cplex rounding be performed?
-  bool get_cplex_rounding() { return cplex_rounding_; }
+  bool get_final_full() const { return final_full_solution_; }
 
   /// Set number of maximum Gauss-Seidel iterations
   void set_local_iters(unsigned int _i) { max_local_iters_ = _i; }
@@ -186,48 +193,41 @@ public:
   }
 
   /// Set time limit for gurobi solver (in seconds)
-  void set_gurobi_max_time(double _d) { gurobi_max_time_ = _d; }
+  void set_gurobi_max_time(double _d) { max_time_ = _d; }
   /// Get time limit for gurobi solver (in seconds)
-  double get_gurobi_max_time() { return gurobi_max_time_; }
+  double get_gurobi_max_time() { return max_time_; }
   /*@}*/
 
 private:
   void solve_no_rounding(CSCMatrix& _A, Vecd& _x, Vecd& _rhs);
   void solve_direct_rounding(
-      CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round);
+      CSCMatrix& _A, Vecd& _x, Vecd& _rhs, const Veci& _to_round);
   void solve_multiple_rounding(
       CSCMatrix& _A, Vecd& _x, Vecd& _rhs, const Veci& _to_round);
   void solve_iterative(
       CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round, bool _fixed_order);
-  void solve_gurobi(CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round);
-  void solve_cplex(CSCMatrix& _A, Vecd& _x, Vecd& _rhs, Veci& _to_round);
+  void solve_gurobi(CSCMatrix& _A, Vecd& _x, Vecd& _rhs, const Veci& _to_round);
+  void solve_cplex(CSCMatrix& _A, Vecd& _x, Vecd& _rhs, const Veci& _to_round);
 
   // return true if the solution has been improved only by local iterations
   bool update_solution_is_local( 
       const CSCMatrix& _A, Vecd& _x, const Vecd& _rhs, const Vecui& _neigh_i);
 
 private:
+  RoundingType rounding_type_;
+
   // parameters used by the MiSo
   bool initial_full_solution_;
   bool iter_full_solution_;
   bool final_full_solution_;
 
-  bool direct_rounding_;
-  bool no_rounding_;
-  bool multiple_rounding_;
-  bool gurobi_rounding_;
-  bool cplex_rounding_;
-
-  double multiple_rounding_threshold_;
-
   unsigned int max_local_iters_;
   double       max_local_error_;
   unsigned int max_cg_iters_;
   double       max_cg_error_;
-  double       max_full_error_;
 
-  // time limit for Gurobi solver (in seconds)
-  double       gurobi_max_time_;
+  double multiple_rounding_threshold_; // control solve_multiple_rounding()
+  double max_time_; // control the time limit for Gurobi and CPLEX (in seconds)
 
   // the actual solver declarations are hidden in the implementation code
   class DirectSolver;