XPRSaddcbmessage

Purpose

Declares an output callback function, called every time a text line relating to the given XPRSprob 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 five arguments, cbprob, cbdata, msg, msglen and msgtype, and has no return value. Use a NULL value to cancel a callback function.

cbprob

The problem passed to the callback function.

cbdata

The user-defined data passed as data when setting up the callback with XPRSaddcbmessage.

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;
  }
}

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. Visual Basic users must use the alternative function XPRSaddcbmessageVB to define the callback; this is required because of the different way VB handles strings.

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XPRSaddcbmessage