ILOG CPLEX 11.0 User's Manual

◆ workmem in the Interactive OptimizerMore working memory allows the optimizer to transfer less data to and from disk. In fact,the Cholesky factor matrix will not be written to disk at all if its size does not exceed thevalue of the working memory parameter. The default for this parameter is 128 megabytes.When the barrier optimizer operates with memory emphasis, the location of disk storage iscontrolled by the working directory parameter.◆◆WorkDir in Concert TechnologyCPX_PARAM_WORKDIR in the Callable Library◆ workdir in the Interactive OptimizerFor example, to use the directory /tmp/mywork, set the working directory parameter to thestring /tmp/mywork. The value of the working directory parameter should be specified asthe name of a directory that already exists, and ILOG CPLEX will create its workingdirectory as a subdirectory there. At the end of barrier optimization, ILOG CPLEX willautomatically delete any working directories it created, leaving the directory specified by theworking directory parameter intact.PreprocessingFor best performance of the ILOG CPLEX Barrier Optimizer, preprocessing should almostalways be on. That is, use the default setting where the presolver and aggregator are active.While they may use more memory, they also reduce the problem, and problem reduction iscrucial to barrier optimizer performance. In fact, reduction is so important that even whenyou turn off preprocessing, ILOG CPLEX still applies minimal presolving before barrieroptimization.For problems that contain linearly dependent rows, it is a good idea to turn on thepreprocessing dependency parameter. (By default, it is off.) This dependency checker mayadd some preprocessing time, but it can detect and remove linearly dependent rows toimprove overall performance. Table 10.7 shows you the possible settings of DepInd, theparameter that controls dependency checking, and indicates their effects.Table 10.7Setting EffectDependency Checking Parameter DepInd or CPX_PARAM_DEPIND-1 automatic: let CPLEX choose when to use dependency checking0 turn off dependency checking1 turn on only at the beginning of preprocessing2 turn on only at the end of preprocessing3 turn on at beginning and at end of preprocessingILOG CPLEX 11.0 — USER’ S MANUAL 209