Interactive Optimizer Commands

This chapter documents the commands and options of the CPLEX Interactive Optimizer. For examples of their use, see the ILOG CPLEX User's Manual. An appendix of that manual contains a list of Interactive Optimizer commands with cross-references to text where the command or option is used.

To enter an ILOG CPLEX command into the Interactive Optimizer, type its full name or any initial segment sufficient to identify the command uniquely. Most commands and options can be entered with a single letter. When there is a prompt for an entry, a return on a blank line returns the user to the ILOG CPLEX prompt without causing any action. All ILOG CPLEX commands can be entered from a single line or incrementally with prompts.

Whenever input defining a range of items is required, ILOG CPLEX expects two indices separated by the default range character, a hyphen (-). The indices can be names or matrix index numbers. CPLEX automatically sets the default upper and lower limits defining any range to be the lowest and highest possible values. Therefore, either the upper or the lower name or index number on either side of the range character can be left out. A hyphen alone means all items in the range.

Command

Options

Concert Technology Library/Callable Library Equivalent

add

filename

CPXaddrows(), CPXaddcols()

The add command is used to add new constraints and bounds to the current problem. When the add command is executed alone, it results in a mode in which multiple constraints can be entered on consecutive lines. Bounds can be entered after the constraints and following the keyword bounds.

Integer declarations may be added after the keyword binary (for binary variables) or the keyword general (for general integer variables).

Example: Add a new constraint to a problem.

CPLEX> add [return] Enter new constraints and bounds ['end' terminates]: x1 + 2x2 + 3x3 >= 50 [return] end [return] Problem addition successful. CPLEX>

The baropt command directs ILOG CPLEX to solve the problem currently in memory using the ILOG CPLEX barrier optimizer. The barrier optimizer uses a primal-dual logarithmic barrier algorithm to solve the LP problem.

The option specifies what happens when the barrier optimizer terminates (either when optimal or when termination criteria are met). Available options are: stop, primopt, dualopt, or no option at all. Specifying no option means the crossover type is determined by the current setting of the barrier crossover parameter. The option primopt instructs ILOG CPLEX to use a primal crossover algorithm to convert the pure barrier solution to a basic solution. Similarly, dualopt instructs ILOG CPLEX to follow a barrier optimization with a dual crossover. Specifying stop instructs ILOG CPLEX barrier optimizer not to initiate a crossover automatically.

change

option identifier1 identifier2 new-_value

CPXchg_____() /

IloCplex::set_____()

The change command modifies the problem currently in memory. The options are: bounds, coefficient, delete, name, objective, rhs, sense. One or two identifiers indicate the item to change. Identifiers can be specified by name or by number. The right-hand side name, the string rhs, or the number 0 (zero) specifies the right-hand side of a constraint. The number 0 (zero), the string obj, or the name of the objective function identifies the objective function. The argument new_value refers to the new value for the item.

The change command can also query for current values. Enter change option without a new value. ILOG CPLEX then displays the current option value and prompts for a new value. Enter a return without pressing another key to return to the CPLEX> prompt. No changes are made.

Example: Change the upper bound on the variable x2 to the new value 50.

CPLEX> change [return] Change Options: bounds change bounds on a variable coefficient change a coefficient delete delete some part of the problem name change a constraint or variable name objective change objective function value rhs change a right-hand side or network supply/demand value sense change objective function or a constraint sense Change to make: bounds [return] Change bounds on which variable: x2 [return] Change lower or upper bound, or both ['l', 'u', or 'b']: u [return] Present bounds on variable x2: The indicated variable is >= 0. Change upper bound to what ['+inf' for no upper bound]: 50 [return] New bounds on variable 'x2': 0 <= x2 <= 50