Forum Discussion
Are preintsol callbacks threadsafe?
The optimizer documentation states "When the MIP callbacks are called they are MUTEX protected to allow non threadsafe user callbacks." In my Java code for one-tree Benders, if I specify a single thr...
Callbacks are in general thread safe. The error message suggests that you are using the wrong problem reference when interacting with Xpress during a callback.
When interacting with Xpress during a callback, you should use the problem reference that is passed into the callback. The error message you are seeing suggests that you are instead using the global problem instance, i.e., the one on which you called optimize.
The problem reference passed into a callback is a thread-local problem reference. As long as you only use that reference in the callback, your callback is thread-safe with respect to Xpress.
Your single-threaded code works because with only one thread, the problem reference passed into the callback is the global problem.
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