OutFlank Routing: Increasing Throughput in Toroidal Interconnection Networks

We present a new, deadlock-free, routing scheme for toroidal interconnection networks, called OutFlank Routing (OFR). OFR is an adaptive strategy which exploits non-minimal links, both in the source and in the destination nodes. When minimal links are congested, OFR deroutes packets to carefully chosen intermediate destinations, in order to obtain travel paths which are only an additive constant longer than the shortest ones. Since routing performance is very sensitive to changes in the traffic model or in the router parameters, an accurate discrete-event simulator of the toroidal network has been developed to empirically validate OFR, by comparing it against other relevant routing strategies, over a range of typical real-world traffic patterns. On the 16x16x16 (4096 nodes) simulated network OFR exhibits improvements of the maximum sustained throughput between 14% and 114%, with respect to Adaptive Bubble Routing.Comment: 9 pages, 5 figures, to be presented at ICPADS 201

Data Structures for Task-based Priority Scheduling

Many task-parallel applications can benefit from attempting to execute tasks in a specific order, as for instance indicated by priorities associated with the tasks. We present three lock-free data structures for priority scheduling with different trade-offs on scalability and ordering guarantees. First we propose a basic extension to work-stealing that provides good scalability, but cannot provide any guarantees for task-ordering in-between threads. Next, we present a centralized priority data structure based on $k$-fifo queues, which provides strong (but still relaxed with regard to a sequential specification) guarantees. The parameter $k$ allows to dynamically configure the trade-off between scalability and the required ordering guarantee. Third, and finally, we combine both data structures into a hybrid, $k$-priority data structure, which provides scalability similar to the work-stealing based approach for larger $k$, while giving strong ordering guarantees for smaller $k$. We argue for using the hybrid data structure as the best compromise for generic, priority-based task-scheduling. We analyze the behavior and trade-offs of our data structures in the context of a simple parallelization of Dijkstra's single-source shortest path algorithm. Our theoretical analysis and simulations show that both the centralized and the hybrid $k$-priority based data structures can give strong guarantees on the useful work performed by the parallel Dijkstra algorithm. We support our results with experimental evidence on an 80-core Intel Xeon system

Integrated Methodologies for the Analysis and Conservation of the Old Bar (Montenegro): the Case Study of Doge’s Palace

The old town of Bar in Montenegro, a Byzantine settlement rebuilt on the remains of a more ancient town destroyed in the 3rd century during the Roman invasion of Dalmatia, ruled between 1443 and 1571 from the city of Venice and then by the Turks until 1878 is, today, a little over an abandoned village but, at the same time, an extraordinary monument from the past to protect and enhance. Traces of its most glorious past are still recognizable in the ruins and artifacts of daily life become known following recent archaeological excavations. Stari Bar is a site unique, a sort of miracle that fortunately survived the ravages of time and negligence of the men. However, it now runs the risk of being overwhelmed by a frenzy of "intervention" that leaves little room for reflection and that can produce errors, which cannot be remedied in the future. Rather than rebuild a fake medieval city or give way to immobility, risking that the culture of ruin prevail, it is necessary to pursue activities of knowledge, study and promotion allowing local communities (as well as those further afield) to re-appropriate the memory of those architectural and urban spaces, triggering new ideas for their possible regeneration. In this framework, this paper presents the case study of the "Doge's Palace", analyzing this important monument in depth knowledge, in order to formulate a proposal for its conservation and valorisation. The experience here reported responds to the initial phase of a more ambitious project aiming at producing a three dimensional “picture” of the site in its current state: a representation made both through the documentation of the town’s most relevant parts and the use of virtual tours and 3D modelling. This activity intends to support the nomination proposal submitted by Montenegro in 2010 to include Stari Bar in UNESCO’s World Heritage List

A study for the conservation of the architectural Islamic complex of Xhemal in Delvina (Albania)

Water is a fundamental element for Islamic culture and the need to purify themselves before the prayer and religious celebrations is made in special baths - near mosques - called hammam. The hammam is usually a large public service building, but there are particular types of small dimensions and for the exclusive use of a wealthy family or, as in the case study here presented - related to the Islamic complex of Xhemal in Delvina (Albania) - an integral part of a religious centre. Characterised by a singular complexity, the monumental site of Xhemal is composed of some aboveground tombs, a mosque, a tekke, two türbe, a fountain and a hammam indeed, as well as of ancient tall plants (cypresses and plane trees). The building, already listed by the national Institute for Cultural Monuments of Albania, has been the subject of a study carried out by prof. Valter Shtylla at the end of the 70s and classed as a hammam from the medieval period. Provisionally measured only in its plan, it is today in a state of serious deterioration, while an example of great interest. For this reason and, along with the entire complex, since 2008 it has been an object of study by the University of Bergamo and Enna Kore, within the research group formed by the Milan Polytechnic and the University Ca' Foscari, in the framework of the program “Albania tomorrow” co-funded by the Cariplo Foundation, in collaboration with the municipality of Delvina. The complex has recently been subjected to a complete laser scanning survey in order to develop a well-planned preservation and valorisation programme

The difficult relationship between ruins and modernity: the case study of the Mother Church reconstruction in Salemi (Italy)

Located in the heart of Sicily, Salemi, a town of Arab origin and first capital of Italy, was devastated by the powerful earthquake that struck the Belice Valley in January 1968. From that moment on, its historic centre has long been abandoned; a few restoration works have been carried out as it was preferred to reconstruct affected districts in new sites. Nevertheless, Salemi has generally maintained its medieval structure, still preserving the original attractive landscape of perched village, resulting from security and control needs of an area based on agricultural and pastoral economy. At its highest point, next to the majestic Norman castle, re-erected in the 13th century by Frederick II of Swabia, stands the Mother Church, were acted the architects Alvaro Siza Vieira and Roberto Collova. Their project, drafted in the early 80's, can be considered as an emblematic case of architectural conservation and cultural preservation. Remains have been seen here in their profound value as a testimony to memory, turning them into charming and moving scenery for the new square created around. The designers considered the traumatic event has a starting point for an overhaul of the historic urban core of the city. They founded the project on the idea of "opening and offering" this sacred space to the town, accepting and integrating the earthquake effects into the architectural plans. Starting from this experience of consolidation and architectural restoration, recalling in its expression Ruskin's romantic memory, this work intends to highlight the historical and today's difficult relationship between ruins and modernity, improvement and destruction, conservation and new buildings design

Update On The Code Intercomparison and Benchmark For Muon Fluence and Absorbed Dose Induced By An 18-GeV Electron Beam After Massive Iron Shielding

In 1974, Nelson, Kase and Svensson published an experimental investigation on muon shielding around SLAC high-energy electron accelerators. They measured muon fluence and absorbed dose induced by 14 and 18 GeV electron beams hitting a copper/water beamdump and attenuated in a thick steel shielding. In their paper, they compared the results with the theoretical models available at that time. In order to compare their experimental results with present model calculations, we use the modern transport Monte Carlo codes MARS15, FLUKA2011 and GEANT4 to model the experimental setup and run simulations. The results are then compared between the codes, and with the SLAC data.Comment: 14 pp. Presented paper at the 13th Meeting of the task-force on Shielding aspects of Accelerators, Targets and Irradiation Facilities (SATIF-13), HZDR, October 10-12, 2016, Dresden, Germany. arXiv admin note: substantial text overlap with arXiv:1502.0168

Laser Scanner 3D per lo studio e la catalogazione dell’archeologia medievale: la chiesa di Santa Croce in Bergamo

The improvement of new active optical sensors has revolutionized the methods for documenting cultural heritage. The conservation and appreciation of our cultural legacy re¬quire an extensive documentation both in terms of shape, color and geometry as well as the more traditional art-historical features. The incessant development of scientific research today provides new possibilities and tools which are essential to know and use in a responsible and scientific way. In the field of archaeology, the automatic 3D survey is now recognized as an added value compared to traditional practices and the active contribution that this technology can provide to the interpretative phase, cataloguing and promotion of archaeological assets, even through the web, is becoming increasingly clear. On the other hand, even considering the speed of the procedure and the accuracy of measurement, there have been calls for reflection on the role that laser scanning can play in the field of archaeology; this role needs to be clarified and consolidated by conducting new studies and experiments, such as the one presented here that concerns the Church of Santa Croce in Bergamo, a small octagonal Romanesque chapel built in the first half of the 11th century

Processor Allocation for Optimistic Parallelization of Irregular Programs

Optimistic parallelization is a promising approach for the parallelization of irregular algorithms: potentially interfering tasks are launched dynamically, and the runtime system detects conflicts between concurrent activities, aborting and rolling back conflicting tasks. However, parallelism in irregular algorithms is very complex. In a regular algorithm like dense matrix multiplication, the amount of parallelism can usually be expressed as a function of the problem size, so it is reasonably straightforward to determine how many processors should be allocated to execute a regular algorithm of a certain size (this is called the processor allocation problem). In contrast, parallelism in irregular algorithms can be a function of input parameters, and the amount of parallelism can vary dramatically during the execution of the irregular algorithm. Therefore, the processor allocation problem for irregular algorithms is very difficult. In this paper, we describe the first systematic strategy for addressing this problem. Our approach is based on a construct called the conflict graph, which (i) provides insight into the amount of parallelism that can be extracted from an irregular algorithm, and (ii) can be used to address the processor allocation problem for irregular algorithms. We show that this problem is related to a generalization of the unfriendly seating problem and, by extending Tur\'an's theorem, we obtain a worst-case class of problems for optimistic parallelization, which we use to derive a lower bound on the exploitable parallelism. Finally, using some theoretically derived properties and some experimental facts, we design a quick and stable control strategy for solving the processor allocation problem heuristically.Comment: 12 pages, 3 figures, extended version of SPAA 2011 brief announcemen

Percutaneous coronary intervention driven by combined use of intracoronary anatomy and physiology Towards a tailored therapy for coronary artery disease

Coronary angiography classically allows a bidimensional evaluation of the vascular lumen, however with many limitations in the case of eccentric lesions, irregular contour or tortuosity of the vessel.Moreover, it does not enable to assess neither the features of the vessel wall, nor the functional significance of a lesion [1]. Newer technologies are available to overcome these limitations.We present a case of percutaneous coronary revascularization optimized by combined use of two of the most widely used techniques