[Boost-users] Xcode - Slow

Hello there. I am implementing matrix multiplication and am trying to have my stuff run as fast as possible. But then I noticed something strange. Using Xcode, resultmatrix = prod(matrix1,matrix2); is 10 to 16 times slower (with 100x100 matrixes) than simply doing something like that: for(...) for(...) for(..) multiply_things(); And 20 to 40 times slower than a simple threaded approach. Using visual studio, it's 2 times faster than naive multiplication. This is on a release build, with #define BOOST_UBLAS_NDEBUG 1 #define NDEBUG 1 So what gives?