This controls the level of output produced by the Optimizer during optimization. The
possible options are to print all messages or to disable printing altogether. Output is sent to the
screen (
stdout) by default, but may be intercepted by a user function using the user
output callback; see
XPRSsetcbmessage. However, under Windows, no output
from the Optimizer DLL is sent to the screen. The user must define a callback function and print
messages to the screen them self if they wish output to be displayed.