:orphan: How to build math libraries for 64-bit integers =============================================== Before you continue please verify whether you really need 64-bit integers. It is extra work and perhaps not needed. If you decide to build DIRAC for 64-bit integers, you have to link to 64-bit integer aware math library/libraries providing both BLAS and LAPACK. The following things can happen: - Your math library is compiled for 64-bit integers and DIRAC will link and run properly. - Your math library is not compiled for 64-bit integers and DIRAC will not link. - Your math library is not compiled for 64-bit integers and DIRAC will link but stop at runtime. - Your math library is not compiled for 64-bit integers and DIRAC will link and not stop at runtime because you deactivated the self-test and may produce wrong numbers. For cases 2-4 you may have to either: - Verify linking. - Compile your own math library. - Use DIRAC's internal math implementation (slow). - Go back to 32-bit integers. MKL --- MKL provides bindings for 64-bit integers and normally DIRAC should correctly link if you have specified MATH\_ROOT correctly. Atlas ----- It is not trivial but doable to compile your own Atlas library with 64-bit integer support. The difficulty is that you need to compile both LAPACK and Atlas. To do this we recommend to follow the nice example: `Installing ATLAS with full LAPACK on Linux/AMD64 `_.