PACHA: Low Cost Bare Metal Development for Shared Memory Manycore Accelerators

AbstractToday, efficiently implementing an application on shared memory manycore accelerators is a hard task. Linux eases the development, but is not adapted to exploit the maximum of the platform yet. Bare metal programming environments provided with accelerators give a low-overhead access to the platform. However, they increase the complexity of development, mainly due to 4 gaps: each accelerator has its own specific environment; bare metal environments are only supported on the hardware platform or on the proprietary simulator; they have seldom, if ever, execution debugging support; they do not have parallel programming models, and whenever they exist, they are platform-specific.In order to fill the gaps and thus, to lower the barrier to develop on bare metal on shared memory manycore accelerators, we present PACHA. It features two aspects: a low overhead, Platform Agnostic, Close-to-HArdware (PACHA) programming interface, which allows to handle only one version of the application code for all supported accelerators, and an easy-to-use multi-platform development environment, which abstracts the complexity of each accelerator's development environment. With a x86 support and a Linux compatibility, PACHA offers a functional simulator and all the Linux set of debugging tools. Further, based on the programming interface, three parallel execution models have been ported in order to facilitate the devel- opment and comparison of applications. PACHA is currently fully supported for x86 platforms, TILEPro64 and STHORM. A case study on a TILEPro64 is presented: the performance gain using PACHA rather than Linux with OpenMP or Pthread is about 1,8x to 4x, without increasing the development cost