Section: Software

Kaapi - Kernel for Asynchronous, Adaptive, Parallel and Interactive Application

Participants : Vincent Danjean, Thierry Gautier [ correspondant ] , Frédéric Wagner.

Kaapi is an efficient fine grain multithreaded runtime that runs on more than 1000 processors and supports addition/resilience of resources. Kaapi means Kernel for Asynchronous, Adaptive, Parallel and Interactive Application . Kaapi runtime support uses a macro data flow representation to build, schedule and execute programs on distributed architectures. Kaapi allows the programmer to tune the scheduling algorithm used to execute its application. Currently, Kaapi only considers data dependencies between multiple producers and multiple consumers. A high level C++ API, called Athapascan and developed by the APACHE project, is implemented on top of Kaapi. Kaapi provides methods to schedule a data flow on multiple processors and then to evaluate it on a parallel architecture. The important key point is the way communications are handled. At a low level of implementation, Kaapi uses an active message protocol to perform very high performance remote write and remote signalization operations. This protocol has been ported on top of various networks (Ethernet/Socket, Myrinet/GM). Moreover, Kaapi is able to generate broadcasts and reductions that are critical for efficiency.

The performance of applications on top of Kaapi scales on clusters and large SMP machines (Symmetric Multi Processors): the kernel is developed using distributed algorithms to reduce synchronizations between threads and UNIX processes. Kaapi, through the use of the Athapascan interface, has been used to compute combinatorial optimization problems on the French Grid Etoile and Grid5000. SOFA is today key target application for Kaapi software.

X-Kaapi is the basic C library that implements non-blocking adaptive work-stealing. The work stealing algorithm implemented in Kaapi has a predictive cost model. Kaapi is able to report important measures to capture the parallel complexity or parallel bottleneck of an application.

Kaapi is developed for UNIX platform and has been ported on most of the UNIX systems (LINUX, IRIX, Mac OS X); it is compliant with both 32 bits and 64 bits architectures (IA32, G4, IA64, G5, MIPS). All Kaapi related material are available at https://gforge.inria.fr/projects/kaapi/ under CeCILL licence.