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67 research outputs found

Low-Level Haskell Code: Measurements and Optimization Techniques

Author: Peixotto David
Publication venue
Publication date: 06/09/2012
Field of study

Haskell is a lazy functional language with a strong static type system and excellent support for parallel programming. The language features of Haskell make it easier to write correct and maintainable programs, but execution speed often suffers from the high levels of abstraction. While much past research focuses on high-level optimizations that take advantage of the functional properties of Haskell, relatively little attention has been paid to the optimization opportunities in the low-level imperative code generated during translation to machine code. One problem with current low-level optimizations is that their effectiveness is limited by the obscured control flow caused by Haskell's high-level abstractions. My thesis is that trace-based optimization techniques can be used to improve the effectiveness of low-level optimizations for Haskell programs. I claim three unique contributions in this work. The first contribution is to expose some properties of low-level Haskell codes by looking at the mix of operations performed by the selected benchmark codes and comparing them to the low-level codes coming from traditional programming languages. The low-level measurements reveal that the control flow is obscured by indirect jumps caused by the implementation of lazy evaluation, higher-order functions, and the separately managed stacks used by Haskell programs. My second contribution is a study on the effectiveness of a dynamic binary trace-based optimizer running on Haskell programs. My results show that while viable program traces frequently occur in Haskell programs the overhead associated with maintaing the traces in a dynamic optimization system outweigh the benefits we get from running the traces. To reduce the runtime overheads, I explore a way to find traces in a separate profiling step. My final contribution is to build and evaluate a static trace-based optimizer for Haskell programs. The static optimizer uses profiling data to find traces in a Haskell program and then restructures the code around the traces to increase the scope available to the low-level optimizer. My results show that we can successfully build traces in Haskell programs, and the optimized code yields a speedup over existing low-level optimizers of up to 86% with an average speedup of 5% across 32 benchmarks

DSpace at Rice University

New fossil remains of Homo naledi from the Lesedi Chamber, South Africa

Author: Bailey S.E.
Berger L.R.
Boshoff P.
Brophy J.K.
Campbell T.L.
Churchill S.E.
de Ruiter D.J.
Delezene L.K.
DeSilva J.M.
Dirks P.H.G.M.
Elliott M.
Feuerriegel E.M.
Garvin H.M.
Gurtov A.
Hawks J.
Hilbert-Wolf H.
Hlophe N.
Hunter R.
Kivell T.L.
Kruger A.
Kuhn B.
Laird M.F.
Meyer M.R.
Morris H.
Peixotto B.
Ramalepa M.
Randolph-Quinney P.
Roberts E.M.
Schmid P.
Skinner M.M.
Tawane G.
Tocheri M.W.
Tsikoane M.
Tucker S.
van Rooyen D.
VanSickle C.
Walker C.S.
Williams S.A.
Publication venue: eLife Sciences Publications Ltd
Publication date: 01/05/2017
Field of study

The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further exploration led to the discovery of hominin material, now comprising 131 hominin specimens, within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present. The hominin remains represent at least three individuals based upon duplication of elements, but more individuals are likely present based upon the spatial context. The most significant specimen is the near-complete cranium of a large individual, designated LES1, with an endocranial volume of approximately 610 ml and associated postcranial remains. The Lesedi Chamber skeletal sample extends our knowledge of the morphology and variation of H. naledi, and evidence of H. naledi from both recovery localities shows a consistent pattern of differentiation from other hominin species.SP201

Wits Institutional Repository on DSPACE