There are many ways to express parallel programs: message-passing libraries (MPI) and multithreading/GPU language extensions such as OpenMP, Pthreads, and CUDA, are but a few. This multitude creates a serious challenge for developers of software verification tools: it takes enormous effort to develop such tools, but each development effort typically targets one small part of the concurrency landscape, with little sharing of techniques and code among efforts.

The Toolkit for Accurate Scientific Software (TASS) is a suite of tools for the formal verification of MPI-based parallel programs used in computational science. TASS can verify various safety properties as well as compare two programs for functional equivalence. The TASS front end takes an integer n ≥ 1 and a C/MPI program, and constructs an abstract model of the program with n processes. Procedures, structs, (multi-dimensional) arrays, heap-allocated data, pointers, and pointer arithmetic are all representable in a TASS model. The model is then explored using symbolic execution and explicit state space enumeration. A number of techniques are used to reduce the time and memory consumed. A variety of realistic MPI programs have been verified with TASS, including Jacobi iteration and manager-worker type programs, and some subtle defects have been discovered. TASS is written in Java and is available from http://vsl.cis.udel.edu/tass under the Gnu Public License.