Example ilolpex6.cpp

ILOG CPLEX 11.0 User's Manual > Continuous Optimization > Solving LPs: Simplex Optimizers > Examples: Using a Starting Basis in an LP Problem > Example ilolpex6.cpp

Example ilolpex6.cpp

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The example, ilolpex6.cpp, resembles one you may have studied in the ILOG CPLEX Getting Started manual, ilolpex1.cpp. This example differs from that one in these ways:

Arrays are constructed using the populatebycolumn method, and thus no command line arguments are needed to select a construction method.
In the main routine, the arrays cstat and rstat set the status of the initial basis.
After the problem data has been copied into the problem object, the basis is copied by a call to cplex.setBasisStatuses.
After the problem has been optimized, the iteration count is printed. For the given data and basis, the basis is optimal, so no iterations are required to optimize the problem.

The main program starts by declaring the environment and terminates by calling method end for the environment. The code in between is encapsulated in a try block that catches all Concert Technology exceptions and prints them to the C++ error stream cerr. All other exceptions are caught as well, and a simple error message is issued. Next the model object and the cplex object are constructed. The function populatebycolumn builds the problem object and, as noted earlier, cplex.setBasisStatuses copies the advanced starting basis.

The call to cplex.solve optimizes the problem, and the subsequent print of the iteration count demonstrates that the advanced basis took effect. In fact, this basis is immediately detected as optimal, resulting in zero iterations being performed, in contrast to the behavior seen in the example program ilolpex1.cpp where the same model is solved without the use of an advanced basis.

The complete program ilolpex6.cpp appears online in the standard distribution at yourCPLEXinstallation/examples/src.

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