DVFS power management in HPC systems

Recent increase in performance of High Performance Computing (HPC) systems has been followed by even higher increase in power consumption. Power draw of modern supercomputers leads to very high operating costs and reliability concerns. Furthermore, it has negative consequences on the environment. Accordingly, over the last decade there have been many works dealing with power/energy management in HPC systems. Since CPUs accounts for a high portion of the total system power consumption, our work aims at CPU power reduction. Dynamic Voltage Frequency Scaling (DVFS) is a widely used technique for CPU power management. Running an application at lower frequency/voltage reduces its power consumption. However, frequency scaling should be used carefully since it has negative effects on the application performance. We argue that the job scheduler level presents a good place for power management in an HPC center having in mind that a parallel job scheduler has a global overview of the entire system. In this thesis we propose power-aware parallel job scheduling policies where the scheduler determines the job CPU frequency, besides the job execution order. Based on the goal, the proposed policies can be classified into two groups: energy saving and power budgeting policies. The energy saving policies aim to reduce CPU energy consumption with a minimal job performance penalty. The first of the energy saving policies assigns the job frequency based on system utilization while the other makes job performance predictions. While for less loaded workloads these policies achieve energy savings, highly loaded workloads suffer from a substantial performance degradation because of higher job wait times due to an increase in load caused by longer job run times. Our results show higher potential of the DVFS technique when applied for power budgeting. The second group of policies are policies for power constrained systems. In contrast to the systems without a power limitation, in the case of a given power budget the DVFS technique even improves overall job performance reducing the average job wait time. This comes from a lower job power consumption that allows more jobs to run simultaneously. The first proposed policy from this group assigns CPU frequency using the job predicted performance and current power draw of already running jobs. The other power budgeting policy is based on an optimization problem which solution determines the job execution order, as well as power distribution among jobs selected for execution. This policy fully exploits available power and leads to further performance improvements. The last contribution of the thesis is an analysis of the DVFS technique potential for energyperformance trade-off in current and future HPC systems. Ongoing changes in technology decrease the DVFS applicability for energy savings but the technique still reduces power consumption making it useful for power constrained systems. In order to analyze DVFS potential, a model of frequency scaling impact on MPI application execution time has been proposed and validated against measurements on a large-scale system. This parametric analysis showed for which application/platform characteristic, frequency scaling leads to energy savings.El aumento de rendimiento que han experimentado los sistemas de altas prestaciones ha venido acompañado de un aumento aún mayor en el consumo de energía. El consumo de los supercomputadores actuales implica unos costes muy altos de funcionamiento. Estos costes no tienen simplemente implicaciones a nivel económico sino también implicaciones en el medio ambiente. Dado la importancia del problema, en los últimos tiempos se han realizado importantes esfuerzos de investigación para atacar el problema de la gestión eficiente de la energía que consumen los sistemas de supercomputación. Dado que la CPU supone un alto porcentaje del consumo total de un sistema, nuestro trabajo se centra en la reducción y gestión eficiente de la energía consumida por la CPU. En concreto, esta tesis se centra en la viabilidad de realizar esta gestión mediante la técnica de Dynamic Voltage Frequency Scalingi (DVFS), una técnica ampliamente utilizada con el objetivo de reducir el consumo energético de la CPU. Sin embargo, esta técnica puede implicar una reducción en el rendimiento de las aplicaciones que se ejecutan, ya que implica una reducción de la frecuencia. Si tenemos en cuenta que el contexto de esta tesis son sistemas de alta prestaciones, minimizar el impacto en la pérdida de rendimiento será uno de nuestros objetivos. Sin embargo, en nuestro contexto, el rendimiento de un trabajo viene determinado por dos factores, tiempo de ejecución y tiempo de espera, por lo que habrá que considerar los dos componentes. Los sistemas de supercomputación suelen estar gestionados por sistemas de colas. Los trabajos, dependiendo de la política que se aplique y el estado del sistema, deberán esperar más o menos tiempo antes de ser ejecutado. Dado las características del sistema objetivo de esta tesis, nosotros consideramos que el Planificador de trabajo (o Job Scheduler), es el mejor componente del sistema para incluir la gestión de la energía ya que es el único punto donde se tiene una visión global de todo el sistema. En este trabajo de tesis proponemos un conjunto de políticas de planificación que considerarán el consumo energético como un recurso más. Estas políticas decidirán que trabajo ejecutar, el número de cpus asignadas y la lista de cpus (y nodos) sino también la frecuencia a la que estas cpus se ejecutarán. Estas políticas estarán orientadas a dos objetivos: reducir la energía total consumida por un conjunto de trabajos y controlar en consumo puntual de un conjunto puntual para evitar saturaciones del sistema en aquellos centros que puedan tener una capacidad limitada (permanente o puntual). El primer grupo de políticas intentará reducir el consumo total minimizando el impacto en el rendimiento. En este grupo encontramos una primera política que asigna la frecuencia de las cpus en función de la utilización del sistema y una segunda que calcula una estimación de la penalización que sufrirá el trabajo que va a empezar para decidir si reducir o no la frecuencia. Estas políticas han mostrado unos resultados aceptables con sistemas poco cargados, pero han mostrado unas pérdidas de rendimiento significativas cuando el sistema está muy cargado. Estas pérdidas de rendimiento no han sido a nivel de incremento significativo del tiempo de ejecución de los trabajos, pero sí de las métricas de rendimiento que incluyen el tiempo de espera de los trabajos (habituales en este contexto). El segundo grupo de políticas, orientadas a sistemas con limitaciones en cuanto a la potencia que pueden consumir, han mostrado un gran potencial utilizando DVFS como mecanismo de gestión. En este caso, comparado con un sistema que no incluya esta gestión, han demostrado mejoras en el rendimiento ya que permiten ejecutar más trabajos de forma simultánea, reduciendo significativamente el tiempo de espera de los trabajos. En este segundo grupo proponemos una política basada en el rendimiento del trabajo que se va a ejecutar y una segunda que considera la asignación de todos los recursos como un problema de optimización lineal. Esta última política es la contribución más importante de la tesis ya que demuestra un buen comportamiento en todos los casos evaluados. La última contribución de la tesis es un estudio del potencial de DVFS como técnica de gestión de la energía en un futuro próximo, en función de un estudio de las características de las aplicaciones, de la reducción de DVFS en el consumo de la CPU y del peso de la CPU dentro de todo el sistema. Este estudio indica que la capacidad de DVFS de ahorrar energía será limitado pero sigue mostrando un gran potencial de cara al control del consumo energético

The role of Duschinsky rotation in intersystem crossing: A case study of uracil

The intersystem crossing rate for the transition between the lowest excited singlet and triplet electronic states of uracil was studied by means of ab initio methods. The rate was evaluated using the timedependent approach based on the correlation function and its two approximations: the second-order cumulant expansion and the short-time approximation. The normal modes of the singlet and triplet states are related by the Duschinsky transformation, i.e., by rotation and translation. It was found that for singlet-triplet adiabatic energy gaps below 6000 cm-1, the inclusion of the Duschinsky rotation is necessary for quantitative results. Above energy gaps of 6000 cm-1, the rates obtained with and without the Duschinsky rotation are similar. The cumulant expansion approximates well the correlation function. The short-time approximation, although crude, can be used as the first estimate of the rate

NEPOSREDNA PRIMENA ČLANA 9, STAVA 3 ARHUSKE KONVENCIJE U PRAVNOM PORETKU REPUBLIKE SRBIJE

The text explores a possibility of direct effect (direct application) of Article 9(3) of the Aarhus Convention in legal order of the Republic of Serbia. The Article guarantees access of the public to administrative or judicial procedures to challenge compatibility of acts of private persons or public authorities with national law relating to environment. In Lesoochranárske zoskupenie the European Court of Justice finds that, according the EU standards on direct effect of international treaties, the Article is not capable to produce direct effect, since contracting parties enjoy a broad discretion to formulate criteria for the public’s access to review procedures. However, the European Court of Justice remained that each member state might have its own standards on direct effect of international treaties and that Slovak courts were obliged to take into account Article 9(3) of the Aarhus Convention when interpreting Slovak procedural law to provide the EU environmental law with best effectiveness. The 2006 Constitution of Serbia foresees direct application of international treaties without limitations and conditions. Still, judicial practice is not fully consistent and it would be premature to derive reliable standards on direct application of international treaties in Serbia. In Serbian legal system there are no particular procedural provisions in environmental law that meet requirements of Article 9(3) of the Aarhus Convention and general procedural provisions depart from these requirements in respect of legal standing. Direct application of Article 9(3) would be possible in such situation as a replacement for missing particular domestic provisions or as supplement of general procedural provisions. The first possibility is less probable. More probable is that a court would search for new interpretation of legal standing in co-effect of domestic general procedural provisions and Article 9(3) of the Aarhus Convention.Rad je posvećen ispitivanju mogućnosti neposredne primene člana 9, stava 3 Arhuske konvencije u pravnom poretku Republike Srbije. Pomenuta odredba Arhuske konvencije odnosi se na pravo javnosti na administrativnu ili sudsku kontrolu poštovanja nacionalnog prava, koje se odnosi na životnu sredinu i ona ne priznaje klasičnu koncepciju pravnog interesa u smislu lične pogođenosti tužioca osporavanim aktom, kao uslova koji treba da ispuni pojedinac da bi vodio upravni ili sudski postupak. Njom ugovornice priznaju da čovek ima ne samo egzistencijalnu potrebu da živi u odgovarajućoj životnoj sredini, već i da se ozbiljno angažuje radi njene zaštite. Ova odredba Arhuske konvencije u sadejstvu sa pravom Republike Srbije o zaštiti životne sredine i procesnim propisima priznaje pravo pojedincu da vodi upravni ili sudski postupak o usaglašenosti činjenja ili propuštanja privatnog lica ili javne vlasti sa nacionalnim pravom koje se odnosi na životnu sredinu i kada pojedinac nije lično pogođen osporavanim aktom

A study of the low-lying singlet and triplet electronic states of chlorophyll A and B

Chlorophylls have been extensively investigated both experimentally and theoretically owing to the fact that they are essential for photosynthesis. We have studied two forms of chlorophyll, chlorophyll a and chlorophyll b, by means of density functional theory. Optimization of S0, S1 and T1 states was performed with the B3-LYP functional. The computed fluorescence lifetimes show good agreement with the available experimental data. The electronic adiabatic energies of S1 and T1 states are 2.09/2.12 and 1.19/1.29 eV for chlorophyll a and chlorophyll b respectively. We discussed the implications of this results on the triplet formation. Also, the calculated vertical ionization potentials shows good agreement with the experimental results. [Projekat Ministarstva nauke Reoublike Srbije, br. 172040

State Succession

State succession has a variety of aspects. Some general rules on State succession exist but these are colored by specific circumstances and there are international customary rules also. All relevant documents define the term “succession” identically as “the replacement of one State by another in the responsibility for the international relations of territory.” Replacement regarding responsibil- ity for the international relations of a territory occurs between a predecessor State and a successor State. Succession has different types or categories such as the cession, decolonization, unification, secession, and dissolution of a State. The rules on succession of States to treaties reconcile freedom of contracting with the general interests of continuity and certainty of treaty relations. One basic principle is the freedom of contracting. In this context it means that new successor States choose the treaties of the predecessor State to which they will enter. The 1978 Convention governs succession by two basic rules (the automatic succession and clean slate rules), and it also governs the case of transfer of a part of territory and the case of unification. The State property, debts, archives, and private rights and the effect of State succession to nationality are fundamental issues

Means of interpretation of international treaties and determinants of their significance

The choice of means of interpretation and attribution appropriate weight to them may well determine the outcome of an interpretation. Articles 31 of the 32 of the VCLT leave broad discretion to an interpreter in that respect. That may turn an interpretation into a legal process of diminishing predictability and undermine legal certainty. Judicious discretion in the choice and weighing means of interpretation should not be unlimited. The nature and particular characteristics of a treaty, of a question that should be answered by interpretation, and of the means of interpretation, might have the role of determinants of the significance of means of interpretation. The correlations in a triangle of the particular characteristics of the treaty, the question and the means of interpretation, established as typical in the practice of international courts, might constitute a standard model of interpretation. An international court would be expected to explain its departure from the model

Interpretation of some bilateral treaties by the International Court of Justice

The text analyzes interpretations of bilateral treaties in three cases decided by the International Court of Justice in the period of 2009 to 2011. As the interpretation of the treaties was performed by applying the same rules laid down in Article 31 and 32 of the Vienna Convention on the Law of Treaties, it includes the same or similar factors and methods. Specific characteristics of each case, in particular the specific characteristics of treaties, resulted in certain differences. The range of factors used in interpretation of a treaty governing a unique issue and the range of factors used in interpretation of a treaty whose object belongs to the class of objects of an area of international law are not the same

The interrelationship between the European Convention on Human Rights and the Aarhus Convention

The Taşkın case manifests mutual supportiveness of the Aarhus Convention and the European Convention on Human Rights as well as of the general international environmental and the right to private and family life. Interactions between the protection of the environment and human rights are complex and involve economic and political factors. Legal concepts of sustainable development, mutual supportiveness and balance of interests bring new principles governing the complex interactions. They are reflected in Taşkın