Improved Acceleration of the GPU Fourier Domain Acceleration Search Algorithm

We present an improvement of our implementation of the Correlation Technique for the Fourier Domain Acceleration Search (FDAS) algorithm on Graphics Processor Units (GPUs) (Dimoudi & Armour 2015; Dimoudi et al. 2017). Our new improved convolution code which uses our custom GPU FFT code is between 2.5 and 3.9 times faster the than our cuFFT-based implementation (on an NVIDIA P100) and allows for a wider range of filter sizes then our previous version. By using this new version of our convolution code in FDAS we have achieved 44% performance increase over our previous best implementation. It is also approximately 8 times faster than the existing PRESTO GPU implementation of FDAS (Luo 2013). This work is part of the AstroAccelerate project (Armour et al. 2002), a many-core accelerated time-domain signal processing library for radio astronomy.Comment: proceeding from ADASS XXVII conference, 4 page

A GPU implementation of the harmonic sum algorithm

Time-domain radio astronomy utilizes a harmonic sum algorithm as part of the Fourier domain periodicity search, this type of search is used to discover single pulsars. The harmonic sum algorithm is also used as part of the Fourier domain acceleration search which aims to discover pulsars that are locked in orbit around another pulsar or compact object. However porting the harmonic sum to many-core architectures like GPUs is not a straightforward task. The main problem that must be overcome is the very unfavourable memory access pattern, which gets worse as the dimensionality of the harmonic sum increases. We present a set of algorithms for calculating the harmonic sum that are more suited to many-core architectures such as GPUs. We present an evaluation of the sensitivity of these different approaches, and their performance. This work forms part of the AstroAccelerate project which is a GPU accelerated software package for processing time-domain radio astronomy data.Comment: 4 pages, 2 figure

Some aspects of the everyday life in DPRK

Bakalářská práce je pokusem o zachycení všedního života mladého člověka, jeho výchovy a vzdělávání v KLDR se zaměřením na hlavní město. Hlavním prostředkem poznávání je záznam vyprávění emigranta o dětství, škole, rodině a dospívání v hlavním městě Korejské lidově demokratické republiky - v Pchjŏngjangu. Sdělení jeho subjektivních prožitků, pozorování a zkušeností, konfrontované s jinými prameny a literaturou, mají významnou vypovídající hodnotu o skutečném obraze života občanů v KLDR, zbavených komunistickým režimem základních lidských práv. Powered by TCPDF (www.tcpdf.org)This bachelor's thesis tries to document everyday life of a young man, fostering and education of him in DPRK with a focus on the capital city. The key source of information is a record of a story of an emigrant about his childhood, school, family and growing-up in the capital city of the Democratic People's Republic of Korea - Pyongyang. His personal experience, observations and knowledge confronted with other sources and literature have expressive value in comprehending the real life of citizens in DPRK deprived of their basic human rights by the communist regime. Powered by TCPDF (www.tcpdf.org)Katedra sinologieDepartment of SinologyFilozofická fakultaFaculty of Art

The Implementation of a Real-Time Polyphase Filter

In this article we study the suitability of dierent computational accelerators for the task of real-time data processing. The algorithm used for comparison is the polyphase filter, a standard tool in signal processing and a well established algorithm. We measure performance in FLOPs and execution time, which is a critical factor for real-time systems. For our real-time studies we have chosen a data rate of 6.5GB/s, which is the estimated data rate for a single channel on the SKAs Low Frequency Aperture Array. Our findings how that GPUs are the most likely candidate for real-time data processing. GPUs are better in both performance and power consumption.Comment: Proceedings of WDS 2014, Charles University in Prague, Faculty of Mathematics and Physics Troja, Pragu

Toward using GANs in astrophysical Monte-Carlo simulations

Accurate modelling of spectra produced by X-ray sources requires the use of Monte-Carlo simulations. These simulations need to evaluate physical processes, such as those occurring in accretion processes around compact objects by sampling a number of different probability distributions. This is computationally time-consuming and could be sped up if replaced by neural networks. We demonstrate, on an example of the Maxwell-J\"uttner distribution that describes the speed of relativistic electrons, that the generative adversarial network (GAN) is capable of statistically replicating the distribution. The average value of the Kolmogorov-Smirnov test is 0.5 for samples generated by the neural network, showing that the generated distribution cannot be distinguished from the true distribution.Comment: Proceedings of ADASS XXXIII (2023

Averaged recurrence quantification analysis: Method omitting the recurrence threshold choice

Recurrence quantification analysis (RQA) is a well established method of nonlinear data analysis. In this work, we present a new strategy for an almost parameter-free RQA. The approach finally omits the choice of the threshold parameter by calculating the RQA measures for a range of thresholds (in fact recurrence rates). Specifically, we test the ability of the RQA measure determinism, to sort data with respect to their signal to noise ratios. We consider a periodic signal, simple chaotic logistic equation, and Lorenz system in the tested data set with different and even very small signal-to-noise ratios of lengths 10 2, 10 3, 10 4, and 10 5. To make the calculations possible, a new effective algorithm was developed for streamlining of the numerical operations on graphics processing unit (GPU)

GPU Fast Convolution via the Overlap-and-Save Method in Shared Memory

We present an implementation of the overlap-and-save method, a method for the convolution of very long signals with short response functions, which is tailored to GPUs. We have implemented several FFT algorithms (using the CUDA programming language), which exploit GPU shared memory, allowing for GPU accelerated convolution. We compare our implementation with an implementation of the overlap-and-save algorithm utilizing the NVIDIA FFT library (cuFFT). We demonstrate that by using a shared-memory-based FFT, we can achieved significant speed-ups for certain problem sizes and lower the memory requirements of the overlap-and-save method on GPUs

Constraining models of twin peak quasi-periodic oscillations with realistic neutron star equations of state

Twin-peak quasi-periodic oscillations (QPOs) are observed in the X-ray power-density spectra of several accreting low-mass neutron star (NS) binaries. In our previous work we have considered several QPO models. We have identified and explored mass-angular-momentum relations implied by individual QPO models for the atoll source 4U 1636-53. In this paper we extend our study and confront QPO models with various NS equations of state (EoS). We start with simplified calculations assuming Kerr background geometry and then present results of detailed calculations considering the influence of NS quadrupole moment (related to rotationally induced NS oblateness) assuming Hartle-Thorne spacetimes. We show that the application of concrete EoS together with a particular QPO model yields a specific mass-angular-momentum relation. However, we demonstrate that the degeneracy in mass and angular momentum can be removed when the NS spin frequency inferred from the X-ray burst observations is considered. We inspect a large set of EoS and discuss their compatibility with the considered QPO models. We conclude that when the NS spin frequency in 4U 1636-53 is close to 580Hz we can exclude 51 from 90 of the considered combinations of EoS and QPO models. We also discuss additional restrictions that may exclude even more combinations. Namely, there are 13 EOS compatible with the observed twin peak QPOs and the relativistic precession model. However, when considering the low frequency QPOs and Lense-Thirring precession, only 5 EOS are compatible with the model.Comment: 12 pages, 9 figures, 3 tables, accepted for publication in The Astrophysical Journa