Section: New Results

Memory consistency for heterogeneous systems

Participant : Ludovic Henrio.

Together with Christoph Kessler (Linköping University), we worked on the formalization of the cache coherency mechanism used in the VectorPU library developed at Linköping University. Running a program on disjoint memory spaces requires to address memory consistency issues and to perform transfers so that the program always accesses the right data. Several approaches exist to ensure the consistency of the memory accessed, we are interested here in the verification of a declarative approach where each component of a computation is annotated with an access mode declaring which part of the memory is read or written by the component. The programming framework uses the component annotations to guarantee the validity of the memory accesses. This is the mechanism used in VectorPU, a C++ library for programming CPU-GPU heterogeneous systems and this article proves the correctness of the software cache-coherence mechanism used in the library. Beyond the scope of VectorPU, this article can be considered as a simple and effective formalisation of memory consistency mechanisms based on the explicit declaration of the effect of each component on each memory space. This year, we have the following new results:

• we extended the work to support the manipulation of overlapping array. This was accepted as an extended version of our conference paper (presented at 4PAD 2018). It will be published in the JLAMP journal in 2020 [3].