Swing modulo scheduling: a lifetime-sensitive approach

This paper presents a novel software pipelining approach, which is called Swing Modulo Scheduling (SMS). It generates schedules that are near optimal in terms of initiation interval, register requirements and stage count. Swing Modulo Scheduling is an heuristic approach that has a low computational cost. The paper describes the technique and evaluates it for the Perfect Club benchmark suite. SMS is compared with other heuristic methods showing that it outperforms them in terms of the quality of the obtained schedules and compilation time. SMS is also compared with an integer linear programming approach that generates optimum schedules but with a huge computational cost, which makes it feasible only for very small loops. For a set of small loops, SMS obtained the optimum initiation interval in all the cases and its schedules required only 5% more registers and a 1% higher stage count than the optimumPeer ReviewedPostprint (published version

Hypernode reduction modulo scheduling

Software pipelining is a loop scheduling technique that extracts parallelism from loops by overlapping the execution of several consecutive iterations. Most prior scheduling research has focused on achieving minimum execution time, without regarding register requirements. Most strategies tend to stretch operand lifetimes because they schedule some operations too early or too late. The paper presents a novel strategy that simultaneously schedules some operations late and other operations early, minimizing all the stretchable dependencies and therefore reducing the registers required by the loop. The key of this strategy is a pre-ordering that selects the order in which the operations will be scheduled. The results show that the method described in this paper performs better than other heuristic methods and almost as well as a linear programming method but requiring much less time to produce the schedules.Peer ReviewedPostprint (published version

Modulo scheduling with reduced register pressure

Software pipelining is a scheduling technique that is used by some product compilers in order to expose more instruction level parallelism out of innermost loops. Module scheduling refers to a class of algorithms for software pipelining. Most previous research on module scheduling has focused on reducing the number of cycles between the initiation of consecutive iterations (which is termed II) but has not considered the effect of the register pressure of the produced schedules. The register pressure increases as the instruction level parallelism increases. When the register requirements of a schedule are higher than the available number of registers, the loop must be rescheduled perhaps with a higher II. Therefore, the register pressure has an important impact on the performance of a schedule. This paper presents a novel heuristic module scheduling strategy that tries to generate schedules with the lowest II, and, from all the possible schedules with such II, it tries to select that with the lowest register requirements. The proposed method has been implemented in an experimental compiler and has been tested for the Perfect Club benchmarks. The results show that the proposed method achieves an optimal II for at least 97.5 percent of the loops and its compilation time is comparable to a conventional top-down approach, whereas the register requirements are lower. In addition, the proposed method is compared with some other existing methods. The results indicate that the proposed method performs better than other heuristic methods and almost as well as linear programming methods, which obtain optimal solutions but are impractical for product compilers because their computing cost grows exponentially with the number of operations in the loop body.Peer ReviewedPostprint (published version

Near-optimal loop tiling by means of cache miss equations and genetic algorithms

The effectiveness of the memory hierarchy is critical for the performance of current processors. The performance of the memory hierarchy can be improved by means of program transformations such as loop tiling, which is a code transformation targeted to reduce capacity misses. This paper presents a novel systematic approach to perform near-optimal loop tiling based on an accurate data locality analysis (cache miss equations) and a powerful technique to search the solution space that is based on a genetic algorithm. The results show that this approach can remove practically all capacity misses for all considered benchmarks. The reduction of replacement misses results in a decrease of the miss ratio that can be as significant as a factor of 7 for the matrix multiply kernel.Peer ReviewedPostprint (published version

Rootstock Effects on Leaf Photosynthesis in 'Navelina' Trees Grown in Calcareous Soil

Citrus crops in the Mediterranean region are often grown in high pH calcareous soils, which promote nutrient imbalances, especially iron deficiency. 'Navelina' trees grafted on eight different citrus rootstocks were assessed in terms of their relative tolerance to these soils. To do so, leaf gas exchange and chlorophyll a fluorescence parameters were measured for 2 consecutive years in leaves without visible injury symptoms. Trees were grown on the rootstocks Carrizo citrange, hybrids of Cleopatra mandarin x Poncirus trifoliata no. 5 (F-A 5),13 (F-A 13), and 16 (030116), Troyer citrange x common mandarin no. 18 (F-A 418), King mandarin x P. trifoliata no. 7 (F-A 517), 020324 (Troyer citrange x Cleopatra mandarin), and Volkamer lemon x P. trifoliata no. 64 (230164). gs and transpiration rate were clearly lower in leaves of shoots grafted on Carrizo citrange than in those on the other rootstocks assayed, but net photosynthetic flux did not differ. However, leaves of shoots on Carrizo citrange displayed a decline in their maximum quantum yield of PSII photochemistry [variable fluorescence/maximum fluorescence (F(v)/F(m)) ratio] and other chlorophyll parameters in the steady state such as photochemical quenching (qp) and the quantum efficiency of PSII photochemistry as well as an increase in nonphotochemical quenching (q(N)). Other rootstocks such as 030116, F-A 517 and, especially, F-A 5 showed the highest Phi(PSU) and F(v)/F(m) values, whereas F-A 5 had the lowest qN in the steady state. The photosynthetic characteristics observed in leaves on Carrizo citrange showed them to be the least tolerant to these calcareous conditions, whereas photosynthesis of 'Navelina' trees budded on F-A 5 were the most tolerant

Acceso a la vivienda y emancipación residencial de los jóvenes españoles en un contexto de crisis

El actual contexto de crisis está generando profundas desigualdades en las condiciones de acceso a la vivienda, dando lugar a grupos sociales especialmente desaventajados. Entre ellos se encuentran los jóvenes españoles, que protagonizan una situación de creciente precariedad económica, agravada por el deterioro del mercado laboral y las limitadas políticas sociales y redistributivas. El presente trabajo analiza las tendencias de las pautas emancipatorias antes y después de la crisis, así como las características del contexto residencial, partiendo de la hipótesis de que, si bien la crisis está aumentando la precariedad residencial de este grupo, la situación de partida era lo suficientemente desfavorable para que se produzcan cambios de tendencias significativos. Los resultados manifiestan, por un lado, que la crisis ha tenido consecuencias en la emancipación revirtiendo el proceso de ligero aumento de la tasa de emancipación residencial que estaba experimentado el colectivo juvenil hasta 2008. Estos efectos afectan desigualmente al colectivo analizado, agudizándose entre los más jóvenes y los peores posicionados en la estructura social. Por otro lado, lo reducido de estas variaciones, pone de manifiesto que las dinámicas emancipatorias son similares a las de los años anteriores a la crisis, sin haberse producido cambios tan acuciantes en las trayectorias residenciales como cabría esperar en un contexto socioeconómico como el actual. Esto se debe, en parte, a que las biografías de los jóvenes ya venían marcadas por un contexto residencial desfavorable caracterizado por un predominio de la vivienda libre en propiedad, elevados precios y la casi inexistencia de un sector de alquiler social, sumado a las condiciones laborales que vienen caracterizando a este colectivo desde hace tiempo

Differential gene expression analysis provides new insights into the molecular basis of iron deficiency stress response in the citrus rootstock Poncirus trifoliata (L.) Raf.

Iron chlorosis is one of the major abiotic stresses affecting fruit trees and other crops in calcareous soils and leads to a reduction in growth and yield. Usual remediation strategies consist of amending iron to soil, which is an expensive practice, or using tolerant cultivars, which are difficult to develop when not available. To understand the mechanisms underlying the associated physiopathy better, and thus develop new strategies to overcome the problems resulting from iron deficiency, the differential gene expression induced by iron deficiency in the susceptible citrus rootstock Poncirus trifoliata (L.) Raf. have been examined. The genes identified are putatively involved in cell wall modification, in determining photosynthesis rate and chlorophyll content, and reducing oxidative stress. Additional studies on cell wall morphology, photosynthesis, and chlorophyll content, as well as peroxidase and catalase activities, support their possible functions in the response to iron deficiency in a susceptible genotype, and the results are discussed

Lightning talks of EduHPC 2022

The lightning talks at EduHPC provide an opportunity to share early results and insights on parallel and distributed computing (PDC) education and training efforts. The four lightning talks at EduHPC 2022 cover a range of topics in broadening PDC education: (i) curriculum development efforts for the European Masters in HPC program, (ii) bootcamps for CI professionals who support the running of AI workloads on HPC systems, (iii) a GPU programming course following the Carpentries model and (iv) peer-review assignments to help students write efficient parallel algorithms within sustainable software libraries.Peer ReviewedArticle signat per 26 autors/es: Apan Qasem 1, Hartwig Anzt 2,3, Eduard Ayguade 4, Katharine Cahill 5, Ramon Canal 4, Jany Chan 6, Eric Fosler-Lussier 6, Fritz Göbel 2, Arpan Jain 6, Marcel Koch 2, Mateusz Kuzak 7, Josep Llosa 4, Raghu Machiraju 6, Xavier Martorell 4, Pratik Nayak 2, Shameema Oottikkal 5, Marcin Ostasz 8, Dhabaleswar K. Panda 6, Dirk Pleiter 9, Rajiv Ramnath 6, Maria-Ribera Sancho 4, Alessio Sclocco 7, Aamir Shafi 6, Hanno Spreeuw 7, Hari Subramoni 6, Karen Tomko 7 / 1 Department of Computer Science, Texas State University, USA; 2 Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany; 3 University of Tennessee (UTK), Knoxville, USA; 4 Barcelona Supercomputing Center and Universitat Politècnica de Catalunya, Spain; 5 Ohio Supercomputer Center, USA; 6 College of Engineering, The Ohio State University, USA; 7 Netherlands eScience Center, The Netherlands; 8 ETP4HPC, The Netherlands; 9 PDC Center for High Performance Computing, KTH Royal Institute of Technology, SwedenPostprint (author's final draft