Hi, I have read the issue of multithreading from 2010 and I wonder whether there has been attempt to make GiNaC thread-safe. I think that it shouldn't be a big deal to make the shared data like the refcounter atomic (e.g. using std::atomic< T >) or to the synchronize it's manipulation (e.g. using std::mutex). Best regards, Florian -- Florian Corzilius RWTH Aachen University Computer Science Department, Informatik 2 D-52056 Aachen, Germany http://www-i2.informatik.rwth-aachen.de/i2/corzilius/ phone: +49 241 80-21244