From 4fdf2ba22184bda0b814daf8ede8187d6a6f556d Mon Sep 17 00:00:00 2001
From: John Forrest <jjhforrest@gmail.com>
Date: Wed, 15 Nov 2023 11:46:50 +0000
Subject: [PATCH] example to show a simple use of event handling

---
 examples/event1.cpp | 176 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 176 insertions(+)
 create mode 100644 examples/event1.cpp

diff --git a/examples/event1.cpp b/examples/event1.cpp
new file mode 100644
index 00000000..f4ae754a
--- /dev/null
+++ b/examples/event1.cpp
@@ -0,0 +1,176 @@
+
+#include <cassert>
+#include <iomanip>
+
+#include "CoinPragma.hpp"
+#include "OsiClpSolverInterface.hpp"
+#include "ClpSimplex.hpp"
+
+//#############################################################################
+
+/************************************************************************
+This keeps track of iterations using event handler
+Coding was thrown together - data should be saved more elagantly
+*/
+#define SAVE_ITS 3
+// Sequence of In variable
+int sequenceIn[SAVE_ITS]={-1};
+// Direction of In, 1 going up, -1 going down, 0 not a clue
+int directionIn[SAVE_ITS]={-1};
+// Sequence of Out variable
+int sequenceOut[SAVE_ITS]={-1};
+// Direction of Out, 1 to upper bound, -1 to lower bound, 0 - superbasic
+int directionOut[SAVE_ITS]={-1};
+// Pivot Row
+int pivot[SAVE_ITS]={-1};
+/** This is so user can trap events and do useful stuff.  
+
+    ClpSimplex model_ is available as well as anything else you care 
+    to pass in
+*/
+
+class MyEventHandler : public ClpEventHandler {
+
+public:
+  /**@name Overrides */
+  //@{
+  virtual int event(Event whichEvent);
+  //@}
+
+  /**@name Constructors, destructor etc*/
+  //@{
+  /** Default constructor. */
+  MyEventHandler();
+  /// Constructor with pointer to model (redundant as setEventHandler does)
+  MyEventHandler(ClpSimplex *model);
+  /** Destructor */
+  virtual ~MyEventHandler();
+  /** The copy constructor. */
+  MyEventHandler(const MyEventHandler &rhs);
+  /// Assignment
+  MyEventHandler &operator=(const MyEventHandler &rhs);
+  /// Clone
+  virtual ClpEventHandler *clone() const;
+  //@}
+
+protected:
+  // data goes here
+};
+//-------------------------------------------------------------------
+// Default Constructor
+//-------------------------------------------------------------------
+MyEventHandler::MyEventHandler()
+  : ClpEventHandler()
+{
+}
+
+//-------------------------------------------------------------------
+// Copy constructor
+//-------------------------------------------------------------------
+MyEventHandler::MyEventHandler(const MyEventHandler &rhs)
+  : ClpEventHandler(rhs)
+{
+}
+
+// Constructor with pointer to model
+MyEventHandler::MyEventHandler(ClpSimplex *model)
+  : ClpEventHandler(model)
+{
+}
+
+//-------------------------------------------------------------------
+// Destructor
+//-------------------------------------------------------------------
+MyEventHandler::~MyEventHandler()
+{
+}
+
+//----------------------------------------------------------------
+// Assignment operator
+//-------------------------------------------------------------------
+MyEventHandler &
+MyEventHandler::operator=(const MyEventHandler &rhs)
+{
+  if (this != &rhs) {
+    ClpEventHandler::operator=(rhs);
+  }
+  return *this;
+}
+//-------------------------------------------------------------------
+// Clone
+//-------------------------------------------------------------------
+ClpEventHandler *MyEventHandler::clone() const
+{
+  return new MyEventHandler(*this);
+}
+
+int MyEventHandler::event(Event whichEvent)
+{
+  if (whichEvent == endOfIteration) {
+    // move up
+    for (int i=SAVE_ITS-2;i>=0;i--) {
+      sequenceIn[i+1] = sequenceIn[i];
+      directionIn[i+1] = directionIn[i];
+      sequenceOut[i+1] = sequenceOut[i];
+      directionOut[i+1] = directionOut[i];
+      pivot[i+1] = pivot[i];
+    }      
+    sequenceIn[0] = model_->sequenceIn();
+    directionIn[0] = model_->directionIn();
+    sequenceOut[0] = model_->sequenceOut();
+    directionOut[0] = model_->directionOut();
+    pivot[0] = model_->pivotRow();
+  }
+  return -1;
+}
+
+int main(int argc, const char *argv[])
+{
+#ifndef OSICLP
+  // using ClpSimplex
+  ClpSimplex model;
+#else
+  OsiClpSolverInterface solver1;
+#endif
+  // Read in model using argv[1]
+  // and assert that it is a clean model
+  std::string mpsFileName;
+  if (argc >= 2) {
+    mpsFileName = argv[1];
+#ifndef OSICLP
+    int numMpsReadErrors = model.readMps(mpsFileName.c_str());
+#else
+    int numMpsReadErrors = solver1.readMps(mpsFileName.c_str(), "");
+#endif
+    if (numMpsReadErrors != 0) {
+      printf("%d errors reading MPS file\n", numMpsReadErrors);
+      return numMpsReadErrors;
+    }
+  } else {
+    printf("Need mps file\n");
+    return -1;
+  }
+  // allow Clp to track iterations
+  MyEventHandler clpEventHandler;
+#ifndef OSICLP
+  ClpSimplex * simplex = &model;
+#else
+  // go over to Clp
+  ClpSimplex * simplex = solver1.getModelPtr();
+#endif
+  simplex->passInEventHandler(&clpEventHandler);
+  // If tiny problem more output
+  if (simplex->numberRows()<40)
+    simplex->setLogLevel(63);
+  simplex->primal();
+  /* print last few iterations
+     then can change basis etc */
+  printf("last few iterations\n");
+  int numberIterations = simplex->numberIterations();
+  for (int i=0;i<SAVE_ITS;i++) {
+    printf("Iteration %d in %d direction %d out %d direction %d pivotrow %d\n",
+	   numberIterations-i,sequenceIn[i],directionIn[i],
+	   sequenceOut[i],directionOut[i],pivot[i]);
+  }
+  return 0;
+}