ILOG CPLEX 11.0 User's Manual

Parameter RoutinesYou can set many parameters in the ILOG CPLEX environment to control its operation. Thevalues of these parameters may be integer, double, or character strings, so there are sets ofroutines for accessing and setting them. Table 4.2 shows you the names and purpose of theseTable 4.2 Callable Library Routines for Parameters in the ILOG CPLEX EnvironmentType Change value Access current value Access default, max, mininteger CPXsetintparam CPXgetintparam CPXinfointparamdouble CPXsetdblparam CPXgetdblparam CPXinfodblparamstring CPXsetstrparam CPXgetstrparam CPXinfostrparamroutines. Each of these routines accepts the same first argument: a pointer to theILOG CPLEX environment (that is, the pointer returned by CPXopenCPLEX). The secondargument of each of those parameter routines is the parameter number, a symbolic constantdefined in the header file, cplex.h. Managing Parameters from the Callable Library onpage 123 offers more details about parameter settings.Null ArgumentsCertain ILOG CPLEX routines that accept optional arguments allow you to pass a NULLpointer in place of the optional argument. The documentation of those routines in theILOG CPLEX Reference Manual indicates explicitly whether NULL pointer arguments areacceptable. (Passing NULL arguments is an effective way to avoid allocating unnecessaryarrays.)Row and Column ReferencesConsistent with standard C programming practices, in ILOG CPLEX an array containing kitems will contain these items in locations 0 (zero) through k-1. Thus a linear program withm rows and n columns will have its rows indexed from 0 to m-1, and its columns from 0to n-1.Within the linear programming data structure, the rows and columns that representconstraints and variables are referenced by an index number. Each row and column mayoptionally have an associated name. If you add or delete rows, the index numbers usuallychange:◆◆for deletions, ILOG CPLEX decrements each reference index above the deletion point;andfor additions, ILOG CPLEX makes all additions at the end of the existing range.118 ILOG CPLEX 11.0 — USER’ S MANUAL