Scalable Task-Based Algorithm for Multiplication of Block-Rank-Sparse Matrices

A task-based formulation of Scalable Universal Matrix Multiplication Algorithm (SUMMA), a popular algorithm for matrix multiplication (MM), is applied to the multiplication of hierarchy-free, rank-structured matrices that appear in the domain of quantum chemistry (QC). The novel features of our formulation are: (1) concurrent scheduling of multiple SUMMA iterations, and (2) fine-grained task-based composition. These features make it tolerant of the load imbalance due to the irregular matrix structure and eliminate all artifactual sources of global synchronization.Scalability of iterative computation of square-root inverse of block-rank-sparse QC matrices is demonstrated; for full-rank (dense) matrices the performance of our SUMMA formulation usually exceeds that of the state-of-the-art dense MM implementations (ScaLAPACK and Cyclops Tensor Framework).Comment: 8 pages, 6 figures, accepted to IA3 2015. arXiv admin note: text overlap with arXiv:1504.0504

Planning the digitisation, storage and access of large scale audiovisual archives

This paper presents ongoing work in PrestoSpace on how broadcast archives can plan large-scale, long-term digitization and storage projects. In our approach, carrier decay, technical obsolescence, and rapidly falling costs of mass storage are represented as a series of statistical and predictive models. The models include ongoing migration within a digital archive. The objective is to allow archive managers to investigate the trade-offs between how many items to transfer, the cost of transfer and storage, how long it will take, what quality can be achieved, how much will be lost, and what digital storage solutions to adopt over time. The process and models are based on digitization projects conducted by large broadcast archives that are currently migrating their collections into digital form. Whilst our focus is on broadcast archives, our findings should be readily transferable to other scenarios where there is a need to store large volumes of digital data over long periods of time

CP violation at one loop in the polarization-independent chargino production in e+e- collisions

Recently Osland and Vereshagin noticed, based on sample calculations of some box diagrams, that in unpolarised e+e- collisions CP-odd effects in the non-diagonal chargino-pair production process are generated at one-loop. Here we perform a full one-loop analysis of these effects and point out that in some cases the neglected vertex and self-energy contributions may play a dominant role. We also show that CP asymmetries in chargino production are sensitive not only to the phase of mu parameter in the chargino sector but also to the phase of stop trilinear coupling A_t.Comment: 14 pages, 5 figure

Judicial Ability and Securities Class Actions

We exploit a new data set of judicial rulings on motions in order to investigate the relationship between judicial ability and judicial outcomes. The data set consists of federal district judges’ rulings on motions to dismiss, to approve the lead plaintiff, and to approve attorneys’ fees in securities class actions cases, and also judges’ decisions to remove themselves from cases. We predict that higher-quality judges, as measured by citations, affirmance rates, and similar criteria, are more likely to dismiss cases, reject lead plaintiffs, reject attorneys’ fees, and retain cases rather than hand them over to other judges. Our results are mixed, providing some but limited evidence for the hypotheses

The Dynamics of Contract Evolution

Contract scholarship has given little attention to the production process for contracts. The usual assumption is that the parties will construct the contract ex nihilo, choosing all the terms so that they will maximize the surplus from the contract. In fact, parties draft most contracts by slightly modifying the terms of contracts that they have used in the past, or that other parties have used in related transactions. A small literature on boilerplate recognizes this phenomenon, but little empirical work examines the process. This Article provides an empirical analysis by drawing on a data set of sovereign bonds. The authors show that exogenous factors are key determinants in the evolution of these contracts. We find an evolutionary pattern that roughly separates into three stages. Stage one where a particular standard form dominates; stage two where there are external shocks and marginal players experiment with deviations from the standard form; and stage three where a new standard emerges. The pattern confirms roughly to the S curve commonly described in the product innovation literature. The authors also find that more marginal law firms are likely to be leaders in innovation at early stages of the innovation cycle but that dominant law firms are the leaders at later stages

The Law and Policy of Judicial Retirement

Lifetime tenure maximizes judicial independence by shielding judges from political pressures, but it creates problems of its own. As is widely known, judges with judicial independence may implement their political preferences or shirk in other ways. Less attention has been given to another problem: that judges will remain in office after their abilities degrade as a result of old age. The U.S. federal system addresses these problems in an indirect way. When judges’ pensions vest, they receive a full salary regardless of whether they work or not; thus, the effective compensation for judicial work falls to zero. Judges can retire, receive their pension, and obtain paying work elsewhere. This approach limits some of the harmful effects of judicial independence by encouraging judges to vacate their offices when they reach a certain age, and by causing judges who lack talent, and therefore find their work burdensome, to self-select themselves out of office. But this solution is hardly perfect. Wealthier judges will be insulated from the financial incentives, and judges with strong partisan preferences can time their retirement for political purposes. We test the potential benefits and costs of this system using a database of federal district judges

Pricing Terms in Sovereign Debt Contracts: A Greek Case Study With Implications for the European Crisis Resolution Mechanism

Conventional wisdom holds that boilerplate contract terms are ignored by parties, and thus are not priced into contracts. We test this view by comparing Greek sovereign bonds that have Greek choice-of-law terms and Greek sovereign bonds that have English choice-of-law terms. Because Greece can change the terms of Greek-law bonds unilaterally by changing Greek Law, and cannot change the terms of English-law bonds, Greek-law bonds should be riskier, with higher yields and lower prices. The spread between the two types of bonds should increase when the probability of Greek default increases. Recent events allow us to test this hypothesis, and the data are consistent with it. We suggest that sovereigns, like private entities, minimize their cost of credit by offering investors with different risk preferences bonds with different levels of risk, which is reflected in their terms, including choice-of-law clauses. The market understands this practice. This finding has implications for the design of the European Crisis Resolution Mechanism (ECRM), which is currently being debated. To the extent the goal of the new restructuring mechanism is to force private investors to take better precautions, ex ante, the restructuring authorities would be well advised to abandon the past practice of largely ignoring variations in the boilerplate of sovereign debt contracts and giving equal treatment to different types of debt

Local well-posedness of the generalized Cucker-Smale model

In this paper, we study the local well-posedness of two types of generalized Cucker-Smale (in short C-S) flocking models. We consider two different communication weights, singular and regular ones, with nonlinear coupling velocities $v|v|^{\beta-2}$ for $\beta > \frac{3-d}{2}$. For the singular communication weight, we choose $\psi^1(x) = 1/|x|^{\alpha}$ with $\alpha \in (0,d-1)$ and $\beta \geq 2$ in dimension $d > 1$. For the regular case, we select $\psi^2(x) \geq 0$ belonging to (L_{loc}^\infty \cap \mbox{Lip}_{loc})(\mathbb{R}^d) and $\beta \in (\frac{3-d}{2},2)$. We also remark the various dynamics of C-S particle system for these communication weights when $\beta \in (0,3)$