Storage constraint satisfaction for embedded processor compilers

Increasing interest in the high-volume high-performance embedded processor market motivates the stand-alone processor world to consider issues like design flexibility (synthesizable processor core), energy consumption, and silicon efficiency. Implications for embedded processor architectures and compilers are the exploitation of hardware acceleration, instruction-level parallelism (ILP), and distributed storage files. In that scope, VLIW architectures have been acclaimed for their parallelism in the architecture while orthogonality of the associated instruction sets is maintained. Code generation methods for such processors will be pressured towards an efficient use of scarce resources while satisfying tight real-time constraints imposed by DSP and multimedia applications. Limited storage (e.g. registers) availability poses a problem for traditional methods that perform code generation in separate stages, e.g. operation scheduling followed by register allocation. This is because the objectives of scheduling and register allocation cause conflicts in code generation in several ways. Firstly, register reuse can create dependencies that did not exist in the original code, but can also save spilling values to memory. Secondly, while a particular ordering of instructions may increase the potential for ILP, the reordering due to instruction scheduling may also extend the lifetime of certain values, which can increase the register requirement. Furthermore, the instruction scheduler requires an adequate number of local registers to avoid register reuse (since reuse limits the opportunity for ILP), while the register allocator would prefer sufficient global registers in order to avoid spills. Finally, an effective scheduler can lose its achieved degree of instruction-level parallelism when spill code is inserted afterwards. Without any communication of information and cooperation between scheduling and storage allocation phases, the compiler writer faces the problem of determining which of these phases should run first to generate the most efficient final code. The lack of communication and cooperation between the instruction scheduling and storage allocation can result in code that contains excess of register spills and/or lower degree of ILP than actually achievable. This problem called phase coupling cannot be ignored when constraints are tight and efficient solutions are desired. Traditional methods that perform code generation in separate stages are often not able to find an efficient or even a feasible solution. Therefore, those methods need an increasing amount of help from the programmer (or designer) to arrive at a feasible solution. Because this requires an excessive amount of design time and extensive knowledge of the processor architecture, there is a need for automated techniques that can cope with the different kinds of constraints during scheduling. This thesis proposes an approach for instruction scheduling and storage allocation that makes an extensive use of timing, resource and storage constraints to prune the search space for scheduling. The method in this approach supports VLIW architectures with (distributed) storage files containing random-access registers, rotating registers to exploit the available ILP in loops, stacks or fifos to exploit larger storage capacities with lower addressing costs. Potential access conflicts between values are analyzed before and during scheduling, according to the type of storage they are assigned to. Using constraint analysis techniques and properties of colored conflict graphs essential information is obtained to identify the bottlenecks for satisfying the storage file constraints. To reduce the identified bottlenecks, this method performs partial scheduling by ordering value accesses such that to allow a better reuse of storage. Without enforcing any specific storage assignment of values, the method continues until it can guarantee that any completion of the partial schedule will also result in a feasible storage allocation. Therefore, the scheduling freedom is exploited for satisfaction of storage, resource, and timing constraints in one phase

Linking farm management and ecosystem service provision: Challenges and opportunities for soil erosion prevention in Mediterranean silvo-pastoral systems

At both local and landscape levels, farm management is the main driver of land cover change influencing ecosystem functions, processes and traits. In Mediterranean large-scale silvo-pastoral systems these changes can have serious implications in the provision of valuable ecosystem services (ES). Current ES assessment, mapping and valuation are still focused in representing the state and trends of ES provision, often missing the link to actual farm management and farm management systems. We propose an approach that, at the farm level, combines the classification of farm management systems with indicators of ES provision. This is illustrated for soil erosion prevention, a key ES in mitigating current and future impacts in Mediterranean regions and the proposed approach is tested in Southern Portugal. We characterize thirty-eight large-scale farm management units (FMU) regarding their management system and environmental traits. Each FMU was then classified according to their management system and a set of ES indicators was calculated. To classify the FMU, data on livestock composition and grazing density, pastures, and soil mobilization practices were object of a cluster analysis and the result was tested against a set of ES indicators. The results highlight the implications and challenges for the provision of soil erosion prevention under different farm management systems and draw a clear relation between more intensive management practices and the degradation of service provision. Our results can also be used to support land management and policy design through the definition of intensity thresholds that consider the local environmental and ecological condition

Policy impacts on regulating ecosystem services: looking at the implications of 60 years of landscape change on soil erosion prevention in a Mediterranean silvo-pastoral system

Context: Policy decisions form a major driver of land use change, with important implications for socially and environmentally susceptible regions. It is well known that there can be major unintended consequences, especially where policies are not tailored to regionally specific contexts. Objectives: In this paper we assess the implications of 60 years of agricultural policies on soil erosion prevention (SEP) by vegetation, an essential regulating ecosystem service in Mediterranean Europe. Methods: To assess these implications we produced and analysed a time series of land cover/use and environmental conditions datasets (from 1951 to 2012) in relation to changing agricultural policies for a specific region in the southern Portugal. A set of indicators related to SEP allowed us to identify that land use intensification as increased soil erosion in the last 60 years. Results: Particularly in the last 35 years, as a consequence of headage payments for cattle, the agricultural policy had a significant effect in the density and renewal of the tree cover, resulting in drastic effects for the provision of the SEP service. These are more significant after 1986, coinciding with the implementation of several Common Agricultural Policy instruments focused on increasing the modernization and productivity capacity of farm systems. Conclusions: The results show some unintended effects of agricultural policy mechanisms on ecosystem service provision and highlight the need for context-based policies, tailored to the environmental constrains and potentials of each region

Estudio de la influencia de los diferentes residuos de carbón como aluminosilicatos en las propiedades mecánicas y la microestructura de los cementos activados alcalinamente

Coal mining wastes are associated with serious environmental problems; they have potential as building materials, including alkali-activated cement. In this study, the effect of different coal mining wastes on the mechanical properties and microstructural development of alkali-activated materials (AAMs) was evaluated through XRD, SEM and FTIR spectroscopy. Different alkali-activated compounds were produced; the alkaline solution was composed of NaOH+Na2SiO3. The results obtained using the calcined coal sludge showed excellent mechanical performance, with compressive strength higher than 60 MPa. However, addition of metakaolin and ordinary Portland cement was necessary to increase the mechanical performance of calcined coal gangue materials. The formation of N-A-S-H gel and the incorporation of iron ions into the cementitious matrix were evidenced. Ultrasonic pulse velocity indicated the early polymerization during the reaction processes. The study verified that the different characteristics of the wastes influence the performance of alkali-activated materials.Los residuos de minería de carbón causan serios problemas ambientales, no obstante, tienen potencial como material de construcción, destacándose los cementos activados alcalinamente. El efecto de los residuos de carbón sobre las propiedades mecánicas y el desarrollo microestructural de los cementos activados alcalinamente son objeto de este estudio. Para ello, se utilizaron las técnicas de DRX, SEM y FTIR. Se produjeron diferentes compuestos activados alcalinamente, utilizando NaOH + Na2SiO3 como activador alcalino y curado térmico (50 °C durante 24 h). Los resultados obtenidos a partir del lodo de carbón calcinado mostraron un excelente rendimiento mecánico, con una resistencia a la compresión superior a 60 MPa. Sin embargo, en el caso de los materiales obtenidos a partir de la ganga de carbón calcinada, fue necesaria la adición de metacaolín y cemento Portland para aumentar sus resistencias mecánicas. Asimismo, se evidenció la formación de gel N-A-S-H y la incorporación de iones de hierro en la matriz cementante. El ensayo de velocidad de pulso ultrasónica indicó la polimerización inicial durante el proceso de reacción. Gracias a este se ha comprobado que las diferentes características de los residuos influyen en las propiedades y comportamiento de los correspondientes materiales activados alcalinamente

Assessing the ability of rural areas to fulfill multiple societal demands

Rural areas are changing through a process of multifunctional transition. New societal expectations, including countryside consumption and protection, increasingly determine the way rural space is used. There is a pressing need to grasp the new relative balance between these drivers of the rural space, in each particular area, in order to target public intervention. Tackling differentiation within rural space will definitely contribute to developing the potential and vocation of each area while supporting territorial cohesion. In this context, sound analytical knowledge that reveals and characterizes this differentiation is required and novel analytical approaches are needed for this knowledge to be obtained. Based on the conceptual framework proposed by Holmes (2006, 2012), this paper presents two methodological pathways for defining a typology of European regions that considers the multifunctionality of rural areas today and the relative weight of the dimensions of production, protection and consumption. The classification is produced at Nomenclature Territorial Unit NUTS 2 level, using information derived from European statistical datasets compiling different cartographic sources. One of the methods used to develop a typology was a clustering approach while the other method used was an expert-based analytical procedure. Even when the limitations stemming from the data available for the whole of Europe are considered, the results are encouraging. The results show two different regional distributions in Europe. These distributions, which have some similarities but also certain differences, both reveal the general characteristics of NUTS 2 regions and shed new light on the ways in which societal expectations for production, protection and consumption might be spatially reconciled. The expert-based approach seems to produce a more faithful classification. Both typologies result in most regions being classified as pluri-active, or complex or multifunctional, which may indicate that multiple modes of rural occupancy are widely found in each region and therefore that a more detailed scale of analysis would be more likely to enable evidence-based decisions to be made

Fast Huffman decoding by exploiting data level parallelism

The frame rates and resolutions of digital videos are on the rising edge. Thereby, pushing the compression ratios of video coding standards to their limits, resulting in more complex and computational power hungry algorithms. Programmable solutions are gaining interest to keep up the pace of the evolving video coding standards, by reducing the time-to-market of upcoming video products. However, to compete with hardwired solutions, parallelism needs to be exploited on as many levels as possible. In this paper the focus will be on data level parallelism. Huffman coding is proven to be very efficient and therefore commonly applied in many coding standards. However, due to the inherently sequential nature, parallelization of the Huffman decoding is considered hard. The proposed fully flexible and programmable acceleration exploits available data level parallelism in Huffman decoding. Our implementation achieves a decoding speed of 106 MBit/s while running on a 250 MHz processor. This is a speed-up of 24× compared to our sequential reference implementation

Temperature inversion symmetry in the Casimir effect with an antiperiodic boundary condition

We present explicitly another example of a temperature inversion symmetry in the Casimir effect for a nonsymmetric boundary condition. We also give an interpretation for our result.Comment: 4 page

Genetic diversity of breeding popcorn lines determined by SSR markers

Information about genetic dissimilarity is very important to corroborate genealogical relationships and to predict the most heterozygotic hybrid combinations. Eight popcorn S6 lines of diverse germplasm types were evaluated using simple sequence repeats (SSR) markers. Of a total of 51 evaluated polymorphic primers, 15 were used for polymerase chain reaction (PCR) amplification. The genetic distance was estimated by Rogers' modified distance. The different popcorn breeding programs in Brazil are possibly using highly similar base-populations. The genetic similarity of lines P1-3 and P8-1 was lowest, while P3-3 and P8-2 were genetically more similar. The cophenetic correlation showed that the Unweighted Pair-Group Method Using Arithmetic Averages (UPGMA) was reliable to discriminate the genotypes in five groups. The clusters were consistent with the estimates of genetic identity. There was a moderate coincidence degree between the groups and genealogy of lines. Higher levels of heterozygosity are expected from crosses between the group containing lines P3-3 and P7-3 with that of P1-3 and P7-4. Crosses between lines P1-3 and P8-1 are also promising