[Previous] [Next]

XPRSsetcbmessage

Purpose

Declares an output callback function, called every time a text line is output by the Optimizer.

Synopsis

               int XPRS_CC XPRSsetcbmessage(XPRSprob prob, void (XPRS_CC *fop)(XPRSprob my_prob, void *my_object, const 
               char *msg, int len, int msgtype), void *object);
               

Arguments

prob  

The current problem.

fop

The callback function which takes five arguments, my_prob, my_object, msg, len and msgtype, and has no return value. Use a NULL value to cancel a callback function.

my_prob  

The problem passed to the callback function.

my_object  

The user-defined object passed to the callback function.

msg

A null terminated character array (string) containing the message, which may simply be a new line.

len

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.

object  

A user-defined object to be passed to the callback function.

Related Controls

Integer

OUTPUTLOG  
                     

All messages are disabled if set to zero.

Example

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

XPRSsetcbmessage(prob,Message,NULL);

The callback function might resemble:

void XPRS_CC Message(XPRSprob my_prob, void* my_object, 
                     const char *msg, int len, int msgtype)
{
  switch(msgtype)
  {
    case 4:  /* error */
    case 3:  /* warning */
    case 2:  /* dialogue */
    case 1:  /* information */
             printf("%s\n", msg);
             break;
    default: /* exiting - buffers need flushing */
             fflush(stdout);
             break;
  }
}

Further information

1. Any screen output is disabled automatically whenever a user output callback is set.

2. Screen output is never produced by the Optimizer DLL running under Windows. The only way to enable screen output from the Optimizer DLL is to define this callback function and use it to print the messages to the screen (stdout).

3. 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.

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