Additive Preconditioning Research Articles

Sound and extensible renaming for java

Descriptive names are crucial to understand code. However, good names are notoriously hard to choose and manually changing a globally visible name can be a maintenance nightmare. Hence, tool support for automated renaming is an essential aid for developers and widely supported by popular development environments. This work improves on two limitations in current refactoring tools: too weak preconditions that lead to unsoundness where names do not bind to the correct declarations after renaming, and too strong preconditions that prevent renaming of certain programs. We identify two main reasons for unsoundness: complex name lookup rules make it hard to define sufficient preconditions, and new language features require additional preconditions. We alleviate both problems by presenting a novel extensible technique for creating symbolic names that are guaranteed to bind to a desired entity in a particular context by inverting lookup functions. The inverted lookup functions can then be tailored to create qualified names where otherwise a conflict would occur, allowing the refactoring to proceed and improve on the problem with too strong preconditions. We have implemented renaming for Java as an extension to the JastAdd Extensible Java Compiler and integrated it in Eclipse. We show examples for which other refactoring engines have too weak preconditions, as well as examples where our approach succeeds in renaming entities by inserting qualifications. To validate the extensibility of the approach we have implemented renaming support for Java 5 and AspectJ like inter-type declarations as modular extensions to the initial Java 1.4 refactoring engine. The renaming engine is only a few thousand lines of code including extensions and performance is on par with industrial strength refactoring tools.

Additive preconditioning, eigenspaces, and the inverse iteration

We incorporate our recent preconditioning techniques into the classical inverse power (Rayleigh quotient) iteration for computing matrix eigenvectors. Every loop of this iteration essentially amounts to solving an ill conditioned linear system of equations. Due to our modification we solve a well conditioned linear system instead. We prove that this modification preserves local quadratic convergence, show experimentally that fast global convergence is preserved as well, and yield similar results for higher order inverse iteration, covering the cases of multiple and clustered eigenvalues.

Reliable Suction Detection for Patients With Rotary Blood Pumps

All rotary blood pumps (RBPs) are prone to the harmful effects of ventricular collapse or "suction events" because of over-pumping, because they are inherently preload insensitive devices, yet RBP controllers do not comprise a clinically reliable suction detector. We therefore investigated the clinical performance of seven expertly selected time domain indices of suction based on the observed positive spike induced in the RBP impeller speed waveform. Using expert panel classifications, a balanced set of 404 five-second speed snapshots of normal and suction events was created from the impeller speed 25 Hz data in 12 VentrAssist implant patients. Initially, suction index threshold levels were set differently for each patient, giving best sensitivity 95% and specificity 99%. However, analysis of paired combinations of suction indices with fixed thresholds identified one pair giving an acceptable sensitivity of 99.5% and specificity 97.5%; the low number of high speed data samples relative to the speed snapshot mean and maximum OR the largest increase in successive speed maxima. The additional precondition of RBP speed amplitude exceeding a low threshold level allows its more general application to patients with low cardiac contractility. This gives a suction detector with high clinical utility; requiring three index threshold settings only.

Additive preconditioning in matrix computations

AbstractWe combine our novel SVD‐free additive preconditioning with aggregation and other relevant techniques to facilitate the solution of a linear system of equations and other fundamental matrix computations. Our analysis and experiments show the power of our algorithms, guide us in selecting most effective policies of preconditioning and aggregation, and provide some new insights into these and related subjects. Compared to the popular SVD‐based multiplicative preconditioners, our additive preconditioners are generated more readily and for a much larger class of matrices. Furthermore, they better preserve matrix structure and sparseness and have a wider range of applications (e.g., they facilitate the solution of a consistent singular linear system of equations and of the eigen‐problem). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Additive preconditioning and aggregation in matrix computations

We combine our novel SVD-free additive preconditioning with aggregation and other relevant techniques to facilitate the solution of a linear system of equations and other fundamental matrix computations. Our analysis and experiments show the power of our algorithms, guide us in selecting most effective policies of preconditioning and aggregation, and provide some new insights into these and related subjects. Compared to the popular SVD-based multiplicative preconditioners, our additive preconditioners are generated more readily and for a much larger class of matrices. Furthermore, they better preserve matrix structure and sparseness and have a wider range of applications (e.g., they facilitate the solution of a consistent singular linear system of equations and of the eigenproblem).

A practical computational framework for the multidimensional moment-constrained maximum entropy principle

The maximum entropy principle is a versatile tool for evaluating smooth approximations of probability density functions with a least bias beyond given constraints. In particular, the moment-based constraints are often a common prior information about a statistical state in various areas of science, including that of a forecast ensemble or a climate in atmospheric science. With that in mind, here we present a unified computational framework for an arbitrary number of phase space dimensions and moment constraints for both Shannon and relative entropies, together with a practical usable convex optimization algorithm based on the Newton method with an additional preconditioning and robust numerical integration routine. This optimization algorithm has already been used in three studies of predictability, and so far was found to be capable of producing reliable results in one- and two-dimensional phase spaces with moment constraints of up to order 4. The current work extensively references those earlier studies as practical examples of the applicability of the algorithm developed below.

Differential response of coronary collateral channels to atrial pacing and balloon occlusion at angioplasty.

Collateral channels can protect from infarction, even in the presence of a total or sub-total occlusion. Acute re-occlusion following restoration of flow may still lead to ischaemia or infarction. It is unclear whether collaterals respond differently to tachycardia-induced stress and balloon inflation. This study compared the response of collateral-dependent viable myocardium to repetitive atrial pacing with the response to multiple balloon occlusions during percutaneous transluminal coronary angioplasty (PTCA). Fifteen patients undergoing elective single vessel PTCA with well-developed collateral channels supplying the target vessel were recruited. Patients underwent two periods of incremental atrial pacing (P(1); P(2)) followed by two 90-s balloon inflations (I(1); I(2)). Collateral flow velocity was assessed by Doppler flow wire across the target lesion. Evidence of ischaemia was obtained from monitoring of surface ST-segments and by chest pain scores recorded on a visual analogue scale. Retrograde and 'aggregate' flow velocities were significantly lower during I(1) and I(2) than either P(1) or P(2). Reduction in flow velocity was most marked during I(1) compared with P(1) or P(2). Chest pain score was lower during P(2) than P(1) (3.8 +/- 3.5 versus 5.5 +/- 3.0, P < 0.02), although flow velocity was unchanged. Collateral flow velocity is significantly higher during tachycardia-induced stress than balloon occlusion. Restoration of antegrade flow by balloon inflation results in a further reduction in flow during a second inflation, suggesting a functional down-regulation of the collateral channels. Ischaemic symptoms are attenuated with repetitive pacing independent of collateral flow, suggesting an additional preconditioning response.

New Citizens — New Voters? Political Preferences and Voting Intentions of Naturalized Germans: A Case Study in Progress

The third millennium witnesses the introduction of a new naturalization law in Germany. Passed by both chambers of parliament in May 1999, the law can be interpreted as a legislative change in Germany's national identity. From January 1, 2000 on, not only German ancestry but also birth on German soil will qualify for the acquisition of German citizenship. The change is remarkable, even though permanent residency of at least one parent is an additional precondition to acquire German citizenship and, in the case of dual citizenship, a final choice of one citizenship has to be made by the age of 23. The naturalization of foreigners also became easier: eight years of residency instead of the formerly required ten will enable a foreigner to become German. Still criticized by the left of the governing Social Democratic Party (SPD) and the Green Party, as well as by the opposition Party of Democratic Socialism (PDS), these changes in naturalization law nevertheless are the most notable ones in twentieth century Germany.

Multilevel preconditioning based on discrete symmetrization for convection-diffusion equations

The subject of this paper is an additive multilevel preconditioning approach for convection-diffusion problems. Our particular interest is in the convergence behavior for convection-dominated problems which are discretized by the streamline diffusion method. The multilevel preconditioner is based on a transformation of the discrete problem which reduces the relative size of the skew-symmetric part of the operator. For the constant coefficient case, an analysis of the convergence properties of this multilevel preconditioner is given in terms of its dependence on the convection size. Moreover, the results of computational experiments for more general convection-diffusion problems are presented and our new preconditioner is compared to standard multilevel preconditioning.

Protection from preconditioning can be reinstated at various reperfusion intervals

The aim of this study was to evaluate the way in which short-term protection declines and is eventually lost in preconditioning and to determine the efficacy of a second preconditioning at various reperfusion intervals. Male rabbits were divided into six groups. Forty-five minutes (sustained) ischemia followed by 120 minutes reperfusion was applied 60, 65, 70, 75, and 80 minutes after a 5 minute preconditioning (groups A, B, C, D, and E) and in a control group (F) after no preconditioning. The infarct to risk ratio (I/R) was 38.3 +/- 3.5% in group A, 46.0 +/- 7.8% in B, 61.6 +/- 9.7% in C, 68.1 +/- 4.2% in D, 64.5 +/- 7.8% in E, and 61.0 +/- 7.7% in F. Group A had a smaller I/R compared with groups C, D, E, and F (p < 0.05). In another series, groups G, H, and I were exposed to two 5-minute preconditioning stimuli, separated, respectively, by 45, 60, and 75 minutes of reperfusion; 10 minutes after the last preconditioning, the animals were exposed to 45-minutes ischemia and 120 minutes reperfusion. Groups A and D (with the smaller and higher I/R ratio) were also incorporated into this protocol in order to compare the effect of the additional preconditioning with the single one. The I/R ratio was 25.4 +/- 8.5% in group G, 22.8 +/- 7.0% in group H, and 14.7 +/- 4.0% in group I (p = NS). Group D showed a higher I/R compared with groups G, A, and H (p < 0.01), and group I had a smaller I/R compared with groups A (p < 0.01) and D (p < 0.001). Cardioprotection after a first preconditioning declines gradually and is eventually lost. An additional preconditioning is always effective, and the longer the interval from the first preconditioning, the more potent is the effect.

The November 1988 Palestine national council resolutions in Algiers and their aftermath

Although Arafat's 14 December 1988 statement in Geneva was described by PLO spokesmen as an accurate interpretation of the resolutions adopted in Algiers on 15 November by the PLO's Palestine National Council, the disparity between the two statements calls for a detailed examination of the PNC resolutions to determine the current posture and intentions of the PLO. At the Algiers session, a Palestinian Declaration of Independence and a Political were approved. This study examines the PNC resolutions included in those documents in light of Arafat's Geneva Statement and other pronouncements made by top PLO leaders subsequently to the Algiers session. Despite claims to the contrary, nowhere in the PNC resolutions themselves is there any explicit recognition of Israel. Security Council Resolutions 242 and 338, which may be construed as implying recognition of Israel's to exist, were accepted by the PNC only tangentially as a basis for an conference. And that oblique acceptance was further eroded by additional preconditions: acceptance of the Palestinians' right to self‐determination--i. e., an independent state--and of all relevant UN resolutions--some of which contradict 242/338. It has been argued that by partially basing its Declaration of Independence on UN Resolution 181 of 1947, which partitioned Palestine into an Arab state and a Jewish the PNC implicitly accepted Israel's to exist. But the PNC referred to 181 exclusively as a source of international legitimacy for the Palestinian not the Jewish state. Nowhere in its resolutions did the PNC define the borders of the Palestinian state it declared, which by implication would have also defined the borders of Israel it was ready to accept. Subsequent statements by PLO leaders suggest that the PNC may still intend to revitalize its 1974 phase program for the liberation of all Palestinian soil. Furthermore, the PNC rejected direct negotiations with Israel, derogated Israel's sovereign to determine admission and exclusion of would‐be immigrants by insisting on the Palestinians' right of return to all of Palestine, described Israel as a fascist, racist, colonialist state, and took no steps to amend its 1968 Palestine National Covenant, which calls for Israel's destruction. And other than Arafat's Stockholm and Geneva statements to the Western press, virtually all subsequent pronouncements by top PLO leaders--particularly in Arabic--further aggravate the doubts that the PNC genuinely intended to recognize Israel. Just five days after clearly and unambiguously renouncing terrorism in Geneva, Arafat stated that he had meant to condemn, not renounce, terrorism and essentially only to repeat the PNC resolutions on that issue. The PNC had predicated its rejection of terrorism in all its forms on the reaffirmation of several previous formulations, each of which leaves the PLO with complete freedom to conduct terrorist attacks. Language: en