Optimizing parallel reduction operations

A parallel program consists of sets of concurrent and sequential tasks. Often, a reduction (such as array sum) sequentially combines values produced by a parallel computation. Because reductions occur so frequently in otherwise parallel programs, they are good candidates for optimization. Since reductions may introduce dependencies, most languages separate computation and reduction. The Sisal functional language is unique in that reduction is a natural consequence of loop expressions; the parallelism is implicit in the language. Unfortunately, the original language supports only seven reduction operations. To generalize these expressions, the Sisal 90 definition adds user-defined reductions at the language level. Applicable optimizations depend upon the mathematical properties of the reduction. Compilation and execution speed, synchronization overhead, memory use and maximum size influence the final implementation. This paper (1) Defines reduction syntax and compares with traditional concurrent methods; (2) Defines classes of reduction operations; (3) Develops analysis of classes for optimized concurrency; (4) Incorporates reductions into Sisal 1.2 and Sisal 90; (5) Evaluates performance and size of the implementations

Working Paper 105 - Smallholder Agriculture in East Africa: Trends, Constraints and Opportunities

Smallholder agriculture continues to play akey role in African agriculture. This paperinvestigates trends, challenges andopportunities of this sub-sector in EastAfrica through case studies of Kenya,Ethiopia, Uganda and Tanzania. In theseagriculture-based economies, smallholderfarming accounts for about 75 percent ofagricultural production and over 75 percentof employment. However, contributions ofsmallholder farming, and agriculture ingeneral, to the region’s recent rapid growthduring 2005 - 08 have remained limited.Instead, growth was driven by services, inparticular trade. This paper finds that at thenational level, weak institutions, restrictedaccess to markets and credit. These factors,including inadequate infrastructure, haveconstrained productivity growth ofsmallholder farming. Measures needed toimprove productivity of smallholder farmersinclude ease of access to land, training toenhance skills and encourage technologyadoption and innovation, and removal ofobstacles to trade. At the regional and globallevels, international trade barriers need to beaddressed.

An interface between single assignment C and vector Pascal

This dissertation contains an overview of the research I’ve been doing over in Glasgow University, which is mainly a project of developing an interface between two array programming languages, Single Assignment C and Vector Pascal, to combine them together by using the Vector Pascal code generator for Single Assignment C. Single Assignment C provides support for multi-threading but it doesn’t contain any utilization of SIMD technology, and Vector Pascal implements array operations with the help of SIMD instruction sets of modern general processors. Thus my hypothesis is that this combination will let the program enjoy higher run-time performance compared to the one which is only compiled by using Single Assignment C’s compiler. This dissertation explains the detail of designing and implementing this interface between these two languages; and the system to manipulate the three parts, i.e. the interface and the two languages’ compilers together to make them work automatically. The interface is generally developed based on traversal over Syntax Tree and involves works of vectorization and loop unrolling. Meanwhile, a benchmark testing system to validate my hypothesis is created and introduced in this dissertation too, which is accompanied with the testing results and analysis

A survey of sequential and parallel implementation techniques for functional programming languages

This paper surveys sequential and parallel implementation techniques for functional programming languages, as well as optimizations that can improve their performance. Sequential implementations have evolved from simple interpreters to sophisticated super-combinator-based compilers, while most parallel implementations have explored a broad range of techniques. We analyze the purpose and function of each implementation technique and discuss the current state-of-the-art in functional language implementation

Manufacturing of coir fibre-reinforced polymer composites by hot compression technique

This present chapter describes the manufacturing technique and properties of coir fibre-reinforced polypropylene composites manufactured using a hot press machine. The effects of basic chromium sulphate and sodium bicarbonate treatment on the physical and mechanical properties were also evaluated. Chemical treatment and fibre loading generally improved the mechanical properties. Five-hour basic chromium sulphate and sodium bicarbonate-treated coir-polypropylene had the best set of properties among all manufactured composites. Chemical treatment also improved water absorption characteristics. This proves that chemical treatment reduced the hydrophilicity of the coir fibre. Overall the hot compression technique was proved to be successful in manufacturing good quality coir reinforced polypropylene composites

Effects of fiber content and extrusion parameters on the properties of flax fiber - polyethylene composites

Extrusion compounding addresses such problems as the non-homogeneity of the mixture and separation of fiber from the polymer during rotational molding, which consequently affect the mechanical and physical properties of the resulting composites. Using triethoxyvinylsilane as chemical pre-treatment on flax fibers and linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) as polymer matrices, this study focused on the effects of flax fiber content (0%, 12.5% or 25%) and extrusion parameters such as barrel zone temperatures (75-110-120-130-140°C or 75-120-130-140-150°C) and screw speed (110 or 150 rpm) on the extrudate and composite properties (extrudate color, extrudate density, extrudate melt flow index, extrudate morphology, composite color, composite density, composite morphology, composite tensile strength and composite water absorption). A mixture of chemically pre-treated flax fibers and powdered polyethylene matrices underwent extrusion compounding using a twin-screw extruder. The extrudates were then pelletized, ground, rotationally molded and cut into test specimens (composites). The mechanical and physical properties of both the extrudates and the composites from different treatments were then measured and compared. Using multiple linear regression, models were generated to show quantitatively the significant effects of the process variables on the response variables. Finally, using response surface methodology and superposition surface methodology on the preceding data, the following optimum values for fiber content and extrusion parameters were determined: for LLDPE composites, fiber content = 6.25%, temperatures = 75-117.3-127.3-137.3-147.3°C, screw speed = 117.5 rpm; for HDPE composites, fiber content = 5.02%, temperatures = 75-118.1-128.1-138.1-148.1°C, screw speed = 125.56 rpm

Agricultural change and rural class formation in Iringa district, Tanzania

This thesis is a study of rural development policy in Tanzania with special reference to Iringa District. Its principal aim is to assess the ujamaa (rural socialism) programme. However, an historical approach is adopted and the thesis devotes considerable attention to the development of agricultural production, particularly maize and tobacco, in Iringa District. Based upon fieldwork conducted during the author's stay in Tanzania in 1976/77, the thesis draws on a variety of unpublished documentary sources and the testimony of informants.The early chapters discuss pre-colonial Tanganyika, the incorporation of the territory into the international capitalist system, and the role of the colonial state in the rural areas. Infrastructures and forms of exploitation are examined in the context of colonial capital accumulation, and it is suggested that colonial policy underwent significant shifts between the 1930s and the post-war period.The thesis argues that the post-Independence government made a disastrous mistake in generalising an experience with co-operatives which had already shown its negative side in the 1950s. Moreover, the ujamaa policy, originally intended as a policy for self-initiative by peasants, was transformed into a state policy for the compulsory resettlement of the rural population in nucleated villages. As a consequence of this bureaucratic approach towards rural development, agriculture was disrupted, production dropped, the will to work of the producers decreased and mismanagement intensified these problems. In short, the technocratic approach towards agriculture has failed to release the productive forces and change the social relations of production in rural Tanzania

Biomass Characterization and Insulation Optimization Studies

This study indicates how biomass materials can be effectively used as naturally sustainable alternatives to insulation materials. Barley grains and oak leaves, straw, and jute are collected, and crushed into powders/ chopped pieces. The physical characteristics are measured to characterize each powder. The biomass powder reinforced composites are manufactured in varying weight ratios. The density and thermal conductivity of composite materials are measured. The properties of composites compared to those of commercial insulation materials are found to be close to them. Furthermore, genetic algorithms (GA) can be used to achieve multi-objective optimization entailing maximizing insulation (minimizing heat transfer) and simultaneously maximizing sustainability (minimizing carbon footprint) of a designed insulation structure. The two resulting nonlinear competing objective functions will be maximized by means of evolutionary optimization techniques within a defined design space. The multi-objective optimization is achieved by building a Pareto front and determining the points of best compromise between the two objectives