Initializing help system before first use

# XPRSaddcbmessage

Purpose
Declares an output callback function, called every time a text line relating to the given problem is output by the Optimizer. This callback function will be called in addition to any callbacks already added by XPRSaddcbmessage. Note that Optimizer messages passed to the callback do not end with a newline character; the user callback is expected to append such required newline characters itself.
Topic areas
Callback, Logging
Synopsis
`int XPRS_CC XPRSaddcbmessage(XPRSprob prob, void (XPRS_CC *message)(XPRSprob cbprob, void *cbdata, const char *msg, int msglen, int msgtype), void *data, int priority);`
Arguments

prob | The current problem.
message | The callback function, which takes arguments cbprob, cbdata, msg, msglen and msgtype, and has no return value.
cbprob | The problem passed to the callback function.
cbdata | The user-defined data passed as data when setting up the callback.
msg | A null terminated character array (string) containing the message, which may simply be a new line. The total number of bytes (including NUL terminator) will not exceed XPRS_MAXMESSAGELENGTH. If a message needs to be truncated to meet this limit, the last four bytes in msg are set to "...\0".
msglen | The length of the message string, excluding the null terminator.
msgtype | Indicates the type of output message:
1 | information messages;
2 | (not used);
3 | warning messages;
4 | error messages.
A negative value indicates that the Optimizer is about to finish and the buffers should be flushed at this time if the output is being redirected to a file.
data | A user-defined data to be passed to the callback function.
priority | An integer that determines the order in which callbacks of this type will be invoked. The callback added with a higher priority will be called before a callback with a lower priority. Set to 0 if not required.

Related controls
Integer

OUTPUTLOG | All messages are disabled if set to zero.

Example
The following example simply sends all output to the screen ( stdout):

    XPRSaddcbmessage(prob,Message,NULL,0);

The callback function might resemble:

    void XPRS_CC Message(XPRSprob cbprob, void* data,
                         const char *msg, int msglen, int msgtype)
    {
      switch(msgtype)
      {
        case 4:  /* error */
        case 3:  /* warning */
        case 2:  /* not used */
        case 1:  /* information */
                 printf("%s\n", msg);
                 break;
        default: /* exiting - buffers need flushing */
                 fflush(stdout);
                 break;
      }
    }

See also examples addmipsol.c, ComplexUserFunctions.c, els_managedcuts.c, els_usercuts.c, fixbv.c, globjpar.c, glrhspar.c, goalprog.c, knapsack.c, loadlp.c, mipsolenum.c, mipsolpool.c, mostviolated.c, Polygon_initialvalue.c, Polygon_textformula.c, Polygon_tokens.c, Polygon_userfunc.c, Polygon_userfunc_map.c, Polygon_userfunc_mapdelta.c, Polygon_userfunc_multimap.c, Polygon_userfunc_multimapdelta.c, Polygon_userfunc_vecmap.c, Polygon_userfunc_vecmapdelta.c, repair.c, roundint.c, savesol.c, solenum.c, tableau.c, trimloss.c, tsp.c.
Further information
1. Screen output is automatically created by the Optimizer Console only. To produce output when using the Optimizer library, it is necessary to define this callback function and use it to print the messages to the screen ( stdout).
2. This function offers one method of handling the messages which describe any warnings and errors that may occur during execution. Other methods are to check the return values of functions and then get the error code using the ERRORCODE attribute, obtain the last error message directly using XPRSgetlasterror, or send messages direct to a log file using XPRSsetlogfile.
3. Querying problem data or changing controls is not possible within this callback.
Related topics
XPRSremovecbmessage, XPRSaddcbbarlog, XPRSaddcbmiplog, XPRSaddcblplog, XPRSsetlogfile.
Parent Topic Console and Library Functions

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