A survey of heterogeneous computing: concepts and systems

This survey of heterogeneous computing concepts and systems is based on the recently proposed by the authors "EM/sup 3/ " (Execution Modes/Machine Models) taxonomy of computer systems in general. The taxonomy is based on two criteria: the number of execution modes supported by the system and the number of machine models present in the system. Since these two criteria are orthogonal, four classes exist: Single Execution mode/Single machine Model (SESM), Single Execution modes/Multiple machine Models (SEMM), Multiple Execution modes/Single machine Model (MESM), and Multiple Execution modes/Multiple machine Models (MEMM). In Section II, heterogeneous computing concepts are viewed through three phases of the compilation and execution of any heterogeneous application: parallelism detection, parallelism characterization and resource allocation. Parallelism detection phase discovers fine-grain parallelism inside every task. This phase is not an exclusive feature of heterogeneous computing, so it will not be dealt with in greater detail. The assignment of parallelism characterization phase is to estimate the behavior of each task in the application on every architecture in the heterogeneous system. In the parallelism characterization domain, one original taxonomy is given. This taxonomy contains scheme classes such as vector and matrix static and dynamic, implicit and explicit, algorithmic and heuristic and numeric and symbolic. Resource allocation phase determines the place and the moment for execution of every task to optimize certain performance measure related to some criteria. In the resource allocation domain, the existing Casavant-Kuhl taxonomy is extended and used. This well known taxonomy is supplemented with scheme classes such as noncooperative competitive, noncooperative noncompetitive, and load sharing. In Section III, heterogeneous systems characterized with multiple execution modes ("fully" heterogeneous systems falling in the MESM and the MEMM class) are surveyed. The MESM class systems are described and illustrated with three case studies, two of which support SIMD/MIMD and one supports scalar/vector combination of execution modes. The MEMM class systems are described and illustrated with two representative examples of fully heterogeneous networks supporting multiple execution modes. The system software for heterogeneous computing systems is presented according to an original three-dimensional (3-D) taxonomy whose criteria rely on the level of heterogeneity support implementation, the programming approach, and the data access technique applied. In Section III, several representative heterogeneous applications are described with their computation requirements and the systems used for their execution. Each topic covered in the paper contains several concise examples.