Programming models and runtimes

Several millions of execution flows will be executed in ultrascale computing systems (UCS), and the task for the programmer to understand their coherency and for the runtime to coordinate them is unfathomable. Moreover, related to UCS large scale and their impact on reliability, the current static point of view is not more sufficient. A runtime cannot consider to restart an application because of the failure of a single node as statically several nodes will fail every day. Classical management of these failures by the programmers using checkpoint restart is also too limited due to the overhead at such a scale. The article explores programming models and runtimes required to facilitate the task of scaling and extracting performance on continuously evolving platforms, while providing resilience and fault-tolerant mechanisms to tackle the increasing probability of failures throughout the whole software stack.