ILOG CPLEX 11.0 User's Manual

Callable Library). If that parameter is set to zero, then optimization proceeds with the treestored in memory until ILOG CPLEX reaches the tree memory limit (TreLim in ConcertTechnology or CPX_PARAM_TRELIM in the Callable Library). If the node file indicator is setto 1 (the default), then a fast compression algorithm is used on the nodes to try to conservememory, without resorting to writing the node files to disk. If the parameter is set to 2, thennode files are written to disk. If the parameter is set to 3, then nodes are both compressed (asin option 1) and written to disk (as in option 2). Table 14.14 summarizes these differentoptions.Table 14.14 Settings for the Node File Storage ParameterSetting MeaningComments0 no node files optimization continues1 node file in memory and compressed optimization continues (default)2 node file on disk files created in temporary directory3 node file on disk and compressed files created in temporary directoryAmong the memory conservation tactics employed by ILOG CPLEX when the memoryemphasis parameter has been set, the maximum setting for the node file indicator isautomatically chosen, so that node-file storage will go to disk. You may still wish to adjustthe working memory or tree limit parameters to fit the capabilities of your computer.In cases where node files are written to disk, ILOG CPLEX will create a temporarysubdirectory under the directory specified by the working directory parameter (WorkDir inConcert Technology or CPX_PARAM_WORKDIR in the Callable Library). The directorynamed by this parameter must exist before ILOG CPLEX attempts to create node files. Bydefault, the value of this parameter is “.”, which means the current working directory.ILOG CPLEX creates the temporary directory by means of system calls. If the systemenvironment variable is set (on Windows platforms, the environment variable TMP; on UNIXplatforms, the environment variable TMPDIR), then the system ignores the ILOG CPLEXnode-file directory parameter and creates the temporary node-file directory in the locationindicated by its system environment variable. Furthermore, if the directory specified in theILOG CPLEX node-file directory parameter is invalid (for example, if it contains illegalcharacters, or if the directory does not allow write access), then the system chooses alocation according to its own logic.The temporary directory created for node file storage will have a name prefixed by cpx. Thefiles within it will also have names prefixed by cpx.ILOG CPLEX automatically removes the files and their temporary directory when it freesthe branch & cut tree:◆in the Interactive Optimizer,ILOG CPLEX 11.0 — USER’ S MANUAL 295