Patrick Maier, Robert Stewart, Phil Trinder

The HdpH DSLs for Scalable Reliable Computation

ABSTRACT:
The statelessness of functional computations facilitates both
parallelism and fault recovery. Faults and non-uniform communication
topologies are key challenges for emergent large scale parallel
architectures.  We report on HdpH and HdpH-RS, a pair of Haskell DSLs
designed to address these challenges for irregular task-parallel
computations on large distributed-memory architectures.  Both DSLs
share an API combining explicit task placement with sophisticated work
stealing.  HdpH focuses on scalability by making placement and
stealing topology aware whereas HdpH-RS delivers reliability by means
of fault tolerant work stealing.

We present operational semantics for both DSLs and investigate
conditions for semantic equivalence of HdpH and HdpH-RS programs, that
is, conditions under which topology awareness can be transparently
traded for fault tolerance.  We detail how the DSL implementations
realise topology awareness and fault tolerance.  We report an initial
evaluation of scalability and fault tolerance on a 256-core cluster
and on up to 32K cores of an HPC platform.

KEYWORDS:
embedded domain specific languages;
parallelism;
topology awareness;
fault tolerance