ILOG CPLEX 11.0 User's Manual

The option value2 lets you specify a file name to redirect output from a channel.Also in that command, value1 allows you to turn on or off output to the screen. Whenvalue1 is y, output is directed to the screen; when its value is n, output is not directed to thescreen. Table 6.3 summarizes which channels direct output to the screen by default. If achannel directs output to the screen by default, you can leave value1 blank to get the sameeffect as set output channel y.Table 6.3 Channels Directing Output to Screen or to a FileChannel Default value1 Meaningdialog y blank directs output to screen but not to a fileerrors y blank directs output to screen and to a filelogonly n blank directs output only to a file, not to screenresults y blank directs output to screen and to a filewarnings y blank directs output to screen and to a fileCallable Library Routines for Message ChannelsInteractive Optimizer and the Callable Library define several message channels for flexiblecontrol over message output:◆◆◆cpxresults for messages containing status and progress information;cpxerror for messages issued when a task cannot be completed;cpxwarning for messages issued when a nonfatal difficulty is encountered; or when anaction taken may have side-effects; or when an assumption made may have side-effects;◆ cpxlog for messages containing information that would not conventionally be displayedon screen but could be useful in a log file.Output messages flow through message channels to destinations. Message channels areassociated with destinations through their destination list. Messages from routines of theILOG CPLEX Callable Library are assigned internally to one of those predefined channels.Those default channels are C pointers to ILOG CPLEX objects; they are initialized byCPXopenCPLEX; they are not global variables. Your application accesses these objects bycalling the routine CPXgetchannels. You can use these predefined message channels foryour own application messages. You can also define new channels.An application using routines from the ILOG CPLEX Callable Library produces no outputmessages unless the application specifies message handling instructions through one orILOG CPLEX 11.0 — USER’ S MANUAL 151