ILOG CPLEX 11.0 User's Manual

ILOG CPLEX ignores the coefficients; if its value is -1, ILOG CPLEX does the opposite ofwhat the coefficients normally suggest. These settings are summarized in Table 9.8.Table 9.8 CraInd Parameter Settings for the Primal Simplex OptimizerCraIndSettingMeaning for Primal Simplex Optimizer1 Use coefficients of objective function to select basis0 Ignore coefficients of objective function-1 Select basis contrary to one indicated by coefficients of objective functionMemory Management and Problem GrowthILOG CPLEX automatically handles memory allocations to accommodate the changing sizeof a problem object as you modify it. And it manages (using a cache) most changes toprevent inefficiency when the changes will require memory re-allocations.Diagnosing Performance ProblemsWhile some linear programming models offer opportunities for performance tuning, others,unfortunately, entail outright performance problems that require diagnosis and correction.This section indicates how to diagnose and correct such performance problems as lack ofmemory or numeric difficulties.Lack of MemoryTo sustain computational speed, ILOG CPLEX should use only available physical memory,rather than virtual memory or paged memory. Even if your problem data fit in memory,ILOG CPLEX will need still more memory to optimize the problem. When ILOG CPLEXrecognizes that only limited memory is available, it automatically makes algorithmicadjustments to compensate. These adjustments almost always reduce optimization speed. Ifyou detect when these automatic adjustments occur, then you can decide when you need toadd additional memory to your computer to sustain computational speed for your particularproblem.An alternative to obtaining more memory is to conserve memory that is available. Thememory emphasis parameter can help you in this respect.◆◆◆MemoryEmphasis (bool) in Concert TechnologyCPX_PARAM_MEMORYEMPHASIS (int) in the Callable Libraryemphasis memory in the Interactive OptimizerILOG CPLEX 11.0 — USER’ S MANUAL 183