Towards HPC-Embedded Case Study: Kalray and Message-Passing on NoC

Today one of the most important challenges in HPC is the development of computers with a low power consumption. In this context, recently, new embedded many-core systems have emerged. One of them is Kalray. Unlike other many-core architectures, Kalray is not a co-processor (self-hosted). One interesting feature of the Kalray architecture is the Network on Chip (NoC) connection. Habitually, the communication in many-core architectures is carried out via shared memory. However, in Kalray, the communication among processing elements can also be via Message-Passing on the NoC. One of the main motivations of this work is to present the main constraints to deal with the Kalray architecture. In particular, we focused on memory management and communication. We assess the use of NoC and shared memory on Kalray. Unlike shared memory, the implementation of Message-Passing on NoC is not transparent from programmer point of view. The synchronization among processing elements and NoC is other of the challenges to deal with in the Karlay processor. Although the synchronization using Message-Passing is more complex and consuming time than using shared memory, we obtain an overall speedup close to 6 when using Message-Passing on NoC with respect to the use of shared memory. Additionally, we have measured the power consumption of both approaches. Despite of being faster, the use of NoC presents a higher power consumption with respect to the approach that exploits shared memory. This additional consumption in Watts is about a 50%. However, the reduction in time by using NoC has an important impact on the overall power consumption as well

Deconvolving Instrumental and Intrinsic Broadening in Excited State X-ray Spectroscopies

Intrinsic and experimental mechanisms frequently lead to broadening of spectral features in excited-state spectroscopies. For example, intrinsic broadening occurs in x-ray absorption spectroscopy (XAS) measurements of heavy elements where the core-hole lifetime is very short. On the other hand, nonresonant x-ray Raman scattering (XRS) and other energy loss measurements are more limited by instrumental resolution. Here, we demonstrate that the Richardson-Lucy (RL) iterative algorithm provides a robust method for deconvolving instrumental and intrinsic resolutions from typical XAS and XRS data. For the K-edge XAS of Ag, we find nearly complete removal of ~9.3 eV FWHM broadening from the combined effects of the short core-hole lifetime and instrumental resolution. We are also able to remove nearly all instrumental broadening in an XRS measurement of diamond, with the resulting improved spectrum comparing favorably with prior soft x-ray XAS measurements. We present a practical methodology for implementing the RL algorithm to these problems, emphasizing the importance of testing for stability of the deconvolution process against noise amplification, perturbations in the initial spectra, and uncertainties in the core-hole lifetime.Comment: 35 pages, 13 figure

A novel wear-resistant magnetic thin film material based on a Ti1−xFexC1−yTi_{1-x}Fe_xC_{1-y} nanocomposite alloy

In this study we report on the film growth and characterization of thin (approximately 50 nm thick) Ti-Fe-C films deposited on amorphous quartz. The experimental studies have been complemented by first principles density functional theory (DFT) calculations. Upon annealing of as-prepared films, the composition of the metastable Ti-Fe-C film changes. An iron-rich phase is first formed close to the film surface, but with increasing annealing time this phase is gradually displaced toward the film-substrate interface where its position stabilizes. Both the magnetic ordering temperature and the saturation magnetization changes significantly upon annealing. The DFT calculations show that the critical temperature and the magnetic moment both increase with increasing Fe and C-vacancy concentration. The formation of the metastable iron-rich Ti-Fe-C compound is reflected in the strong increase of the magnetic ordering temperature. Eventually, after enough annealing time ($\geq 10$ minutes), nano-crystalline $\alpha$-Fe starts to precipitate and the amount and size of these precipitates can be controlled by the annealing procedure; after 20 minutes of annealing, the experimental results indicate a nano-crystalline iron-film embedded in a wear resistant TiC compound. This conclusion is further supported by transmission electron microscopy studies on epitaxial Ti-Fe-C films deposited on single crystalline MgO substrates where, upon annealing, an iron film embedded in TiC is formed. Our results suggest that annealing of metastable Ti-Fe-C films can be used as an efficient way of creating a wear-resistant magnetic thin film material.Comment: 23 pages, 13 figure

Carbon release by selective alloying of transition metal carbides

We have performed first principles density functional theory calculations on TiC alloyed on the Ti sublattice with 3d transition metals ranging from Sc to Zn. The theory is accompanied with experimental investigations, both as regards materials synthesis as well as characterization. Our results show that by dissolving a metal with a weak ability to form carbides, the stability of the alloy is lowered and a driving force for the release of carbon from the carbide is created. During thin film growth of a metal carbide this effect will favor the formation of a nanocomposite with carbide grains in a carbon matrix. The choice of alloying elements as well as their concentrations will affect the relative amount of carbon in the carbide and in the carbon matrix. This can be used to design the structure of nanocomposites and their physical and chemical properties. One example of applications is as low-friction coatings. Of the materials studied, we suggest the late 3d transition metals as the most promising elements for this phenomenon, at least when alloying with TiC.Comment: 9 pages, 6 figure

Reconstructing phylogenetic level-1 networks from nondense binet and trinet sets

Binets and trinets are phylogenetic networks with two and three leaves, respectively. Here we consider the problem of deciding if there exists a binary level-1 phylogenetic network displaying a given set T of binary binets or trinets over a taxon set X, and constructing such a network whenever it exists. We show that this is NP-hard for trinets but polynomial-time solvable for binets. Moreover, we show that the problem is still polynomial-time solvable for inputs consisting of binets and trinets as long as the cycles in the trinets have size three. Finally, we present an O(3^{|X|} poly(|X|)) time algorithm for general sets of binets and trinets. The latter two algorithms generalise to instances containing level-1 networks with arbitrarily many leaves, and thus provide some of the first supernetwork algorithms for computing networks from a set of rooted 1 phylogenetic networks

A critical analysis of the hydrino model

Recently, spectroscopic and calorimetric observations of hydrogen plasmas and chemical reactions with them have been interpreted as evidence for the existence of electronic states of the hydrogen atom with a binding energy of more than 13.6 eV. The theoretical basis for such states, that have been dubbed hydrinos, is investigated. We discuss both, the novel deterministic model of the hydrogen atom, in which the existence of hydrinos was predicted, and standard quantum mechanics. Severe inconsistencies in the deterministic model are pointed out and the incompatibility of hydrino states with quantum mechanics is reviewed.Comment: 9 page

Materials with periodic internal structure: Computation based on homogenization and comparison with experiment

The combination of thermal and mechanical loading expected in practice means that constitutive equations of metal matrix composites must be developed which deal with time-independent and time-dependent irreversible deformation. Also, the internal state of composites is extremely complicated which underlines the need to formulate macroscopic constitutive equations with a limited number of state variables which represent the internal state at the micro level. One available method for calculating the macro properties of composites in terms of the distribution and properties of the constituent materials is the method of homogenization whose formulation is based on the periodicity of the substructure of the composite. A homogenization procedure was developed which lends itself to the use of the finite element procedure. The efficiency of these procedures, to determine the macroscopic properties of a composite system from its constituent properties, was demonstrated utilizing an aluminum plate perforated by directionally oriented slits. The selection of this problem is based on the fact that, extensive experimental results exist, the macroscopic response is highly anisotropic, and that the slits provide very high stress gradients which severely test the effectiveness of the computational procedures. Furthermore, both elastic and plastic properties were investigated so that the application to practical systems with inelastic deformation should be able to proceed without difficulty. The effectiveness of the procedures was rigorously checked against experimental results and with the predictions of approximate calculations. Using the computational results it is illustrated how macroscopic constitutive equations can be expressed in forms of the elastic and limit load behavior

High-accuracy sampling of saproxylic diversity indicators at regional scales with pheromones: The case of "Elater ferrugineus" (Coleoptera, Elateridae)

The rare beetle Elater ferrugineus was sampled at 47 sites in the county of Östergötland, Sweden by means of pheromone-baited traps to assess its value as an indicator species for hollow oak stands rich in rare saproxylic beetle species. In addition, Osmoderma eremita was also sampled with pheromone baits. These data were then compared against species survey data collected at the same sites by pitfall and window traps. Both species co-occur with many Red Listed saproxylic beetles, with E. ferrugineus being a somewhat better indicator for the rarest species. The conservation value of a site (measured as Red List points or number of Red Listed species) increased with the number of specimens of E. ferrugineus and O. eremita caught. Accuracy of sampling by means of pheromone trapping turned out to be radically different for the two model species. E. ferrugineus traps put out during July obtained full accuracy after only 6 days, whereas O. eremita traps needed to be out from early July to mid-August in order to obtain full accuracy with one trap per site. By using E. ferrugineus, or preferably both species, as indicator species, accuracy would increase and costs decrease for saproxylic biodiversity sampling, monitoring and identification of hotspots