Allinea DDT is a commercial C, C++ and Fortran 90 debugger produced by Allinea Software of Warwick, United Kingdom. It is widely used for debugging parallel MPI and threaded (pthread or OpenMP) programs, including those running on clusters of Linux machines. As of June 2015 it is used on 58 of the top 100 supercomputers on the TOP500 list.It is used to find bugs on both small and large clusters, from 1 to 1,000s of processors.