add modifyCoefficient

Author: jjhforrest

src/Osi/OsiSolverInterface.cpp

@@ -687,6 +687,14 @@ int OsiSolverInterface::addRows(CoinModel &modelObject)
     return -1;
   }
 }
+// modify one coefficient
+void OsiSolverInterface::modifyCoefficient(int row, int column,
+					   double newElement,
+					   bool keepZero)
+{
+  CoinPackedMatrix * matrix = getMutableMatrixByCol();
+  matrix->modifyCoefficient(row, column, newElement, keepZero);
+}
 /*  Strip off rows to get to this number of rows.
     If solver wants it can restore a copy of "base" (continuous) model here
 */

src/Osi/OsiSolverInterface.hpp

@@ -695,7 +695,9 @@ class OSILIB_EXPORT OsiSolverInterface  {
       recognise any modifications to the matrix).
     */
   virtual CoinPackedMatrix *getMutableMatrixByCol() const { return NULL; }
-
+  /// Modify a single element
+  virtual void modifyCoefficient(int row, int column, double newElement,
+				 bool keepZero = false);
   /// Get the solver's value for infinity
   virtual double getInfinity() const = 0;
   //@}