Compiling Communication-Minimizing Query Plans

Because of the low arithmetic intensity of relational database operators, the performance of in-memory column stores ought to be bound by main-memory bandwidth, and in practice, highly-optimized operator implementations already achieve close to their peak theoretical performance. By itself, this would imply that hardware acceleration for analytics would be of limited utility, but I show that the emergence of full-query compilation presents new opportunities to reduce memory traffic and trade computation for communication, meaning that database-oriented processors may yet be worth designing.Moreover, the communication costs of queries on a given processor and memory hierarchy are determined by factors below the level of abstraction expressed in traditional query plans, such as how operators are (or are not) fused together, how execution is parallelized and cache-blocked, and how intermediate results are arranged in memory. I present a Scala- embedded programming language called Ressort that exposes these machine-level aspects of query compilation, and which emits parallel C++/OpenMP code as its target to express a greater range of algorithmic variants for each query than would be easy to study by hand

Rapid Prototyping and Exploration Environment for Generating C-to-Hardware-Compilers

There is today an ever-increasing demand for more computational power coupled with a desire to minimize energy requirements. Hardware accelerators currently appear to be the best solution to this problem. While general purpose computation with GPUs seem to be very successful in this area, they perform adequately only in those cases where the data access patterns and utilized algorithms fit the underlying architecture. ASICs on the other hand can yield even better results in terms of performance and energy consumption, but are very inflexible, as they are manufactured with an application specific circuitry. Field Programmable Gate Arrays (FPGAs) represent a combination of approaches: With their application specific hardware they provide high computational power while requiring, for many applications, less energy than a CPU or a GPU. On the other hand they are far more flexible than an ASIC due to their reconfigurability. The only remaining problem is the programming of the FPGAs, as they are far more difficult to program compared to regular software. To allow common software developers, who have at best very limited knowledge in hardware design, to make use of these devices, tools were developed that take a regular high level language and generate hardware from it. Among such tools, C-to-HDL compilers are a particularly wide-spread approach. These compilers attempt to translate common C code into a hardware description language from which a datapath is generated. Most of these compilers have many restrictions for the input and differ in their underlying generated micro architecture, their scheduling method, their applied optimizations, their execution model and even their target hardware. Thus, a comparison of a certain aspect alone, like their implemented scheduling method or their generated micro architecture, is almost impossible, as they differ in so many other aspects. This work provides a survey of the existing C-to-HDL compilers and presents a new approach to evaluating and exploring different micro architectures for dynamic scheduling used by such compilers. From a mathematically formulated rule set the Triad compiler generates a backend for the Scale compiler framework, which then implements a hardware generation backend with described dynamic scheduling. While more than a factor of four slower than hardware from highly optimized compilers, this environment allows easy comparison and exploration of different rule sets and the micro architecture for the dynamically scheduled datapaths generated from them. For demonstration purposes a rule set modeling the COCOMA token flow model from the COMRADE 2.0 compiler was implemented. Multiple variants of it were explored: Savings of up to 11% of the required hardware resources were possible

COMRADE: A High Level Compiler for Adaptive Computer Systems

Rechenleistung wird klassisch durch schnellere oder zusätzliche Mikroprozessoren gesteigert. Dagegen lagert ein Adaptives Computersystem (ACS) rechenintensive Teile in rekonfigurierbare Hardware (HW) aus. Da die Programmerstellung für ein ACS von Hand Wissen über den Entwurf von Software (SW) und Hardware vom Entwickler verlangt und viel Zeit verbraucht, wurde der Compiler COMRADE entwickelt. COMRADE partitioniert einen C-Quelltext in einen SW-Teil und eine HW-Konfiguration für ein ACS. Dabei werden automatisch Regionen für eine HW-Beschleunigung bestimmt und HW-Konfiguration und SW zu einem lauffähigen Ganzen zusammengesetzt. COMRADE kann durch neue HW-Modulbibliotheken und Konfigurationsdateien leicht an neue Zielarchitekturen angepasst werden. Er unterstützt den vollen C-Sprachumfang. Eine verbesserte HW-SW-Partitionierung vergrößert den synthetisierten HW-Anteil. Heuristiken in COMRADE reduzieren die Nachteile der hohen Rekonfigurationszeiten von aktuellen Logikbausteinen durch Zusammenfassen mehrerer HW-Teile zu Konfigurationen. Ein Großteil der während der Programmausführung auf einem ACS sonst nötigen Konfigurationen kann so eingespart werden. Die Steuerung der HW übernimmt eine neu entwickelte Datenflussmaschine. Neben Hardware-Pipelines werden spekulative Berechnungen unterstützt. Aus mehreren Ergebnissen wird das richtige für die weitere Berechnung ausgewählt. Durch das neuartige Ausführungsmodell ergibt sich gegenüber herkömmlichen spekulativen Mechanismen ein Laufzeitgewinn. Die Anwendung verschiedener Optimierungen auf Hochsprachenebene zeigte wesentlichen Einfluss auf die Größe und die Geschwindigkeit der erzeugten HW. Nachgewiesen wurden der Vorteil jeder einzelnen Optimierung sowie die höhere Effektivität der Kombination von Optimierungen. Durch die in COMRADE implementierten Optimierungen konnten der HW-Verbrauch wie auch die Anzahl der Speicherzugriffe wesentlich reduziert werden.Traditionally, computer performance is increased by using faster or additional processors. Adaptive computers (AC) accelerate applications by executing software (SW) on reconfigurable hardware. The programming of an AC generally requires experience beyond conventional software programming, namely detailed knowledge in hardware (HW) architecture and design. COMRADE helps the programmer to develop program for ACs. It partitions C source code into HW configurations and SW. Automatically, HW regions for acceleration are determined, and these HW configurations are linked to the SW to create the program for the AC. COMRADE is easily adaptable to new target architectures with help of new HW module libraries and configuration files. It supports dusty deck C source code. Improved HW/SW partitioning increases the synthesizable HW part of translated application. Heuristics reduce disadvantages of high reconfiguration times of actual reconfigurable logic chips. It combines several HW configurations to one configuration. Thus, many configurations during the program execution are not needed anymore. The HW execution is controlled by a new developed data flow machine. Besides HW pipelining, speculative executions are supported. The right result is chosen from several in parallel calculated values. Because of the new execution model, the runtime of calculations in HW is increased compared to traditional data flow machines. Several optimizations are included in COMRADE. They achieve better performance and decreased resource requirements of the created HW. Besides advantages of single optimizations, the combination of optimizations showed higher efficiency than every single optimization

Localized Minimum-Latency Broadcasting in Multi-radio Multi-rate Wireless Mesh Networks

Abstract: We address the problem of minimizing the worst-case broadcast delay in multi-rate wireless mesh networks (WMN) in a distributed and localized fashion. Efficient broadcasting in such networks is especially challenging due to the multi-rate transmission capability and the interference between wireless transmissions of WMN nodes. We propose connecting dominating set (CDS) based broadcast routing approach which calculates the set of forwarding nodes and the transmission rate at each forwarding node independent of the broadcast source. Thereafter, a forwarding tree is constructed taking into consideration the source of the broadcast. In this paper, we propose three distributed and localized rate-aware broadcast algorithms. We compare the performance of our distributed and localized algorithms with previously proposed centralized algorithms and observe that the performance gap is not large. We show that our algorithms greatly improve performance of rate-unaware broadcasting algorithms by incorporating rate-awareness into the broadcast tree construction algorithm process. I

Virtual Cell Layout Based Dynamic Source Routing (vb-dsr) For The Mobile Subsystem Of The Next Generation Tactical Communications Systems

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2002Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2002Telsiz ağlar, 1970’lerde ortaya çıkışlarından itibaren bilgisayar endüstrisinde çok yaygınlaşmıştır. Telsiz ağlar gezgin kullanıcılara nerede olduklarına bağlı olmadan heryerde iletişim kurma ve bilgiye erişim imkanı sağlar. Hiçbir sabit altyapıya gerek duymadan bu imkanı sağlayan ad hoc ağların zaman içinde gelişmesiyle ve askeri, ticari ve özel maksatlar için tercih edilir hale gelmesiyle, uygulamada bazı zorluklar başgöstermiştir. Çalışmamızda, bu zorlukları ve ad hoc ağlardan beklenenleri dikkate alarak Sanal Hücre Kalıbı (SHK) tabanlı Dinamik Kaynak Yol Atama (DKYA) yaklaşımını bir çözüm olarak sunuyoruz. SHK, etkili bir özkaynak yönetimi ve ağ ölçeklenebilirliği sağlayan çok-katmanlı öbek-yapılı bir yaklaşımdır. Biz SHK yapısının üzerine Dinamik Kaynak Yolatama protokolunu uyguladık. Sunduğumuz yaklaşım, SHK yapılı DKYA, iki düzeyli hiyerarşik öbek yapılı bir sistemdir. SHK yaklaşımında önerilen benzetim yaklaşımını geliştiriyoruz ve taktik iletişimlerin başarımlarının değerlendirmesinde bu benzetim yaklaşımını kullanıyoruz. Bu yöntemde, önceden gerçekleştirilen bilgisayar destekli askeri tatbikatlarda girilen emirleri, çok sayıdaki birliğe ait hareket, görev ve durum gibi verileri toplayan bir yapıcı (muharebe) model kullanarak tekrar işlemekteyiz. Daha sonra toplanan bu veriler daha da detaylandırılarak, başarı ölçütlerimize ait değerleri üreten benzetim kullanılmaktadır. Sistemi değerlendiren başarım ölçütleri, SHK-tabanlı DKYA’nın gezgin ad hoc ağlardan beklenenleri sağladığını göstermektedir.Wireless networks have become very popular in the computing industry after their emergence in the 1970’s. Wireless networks provide mobile user with ubiquitous communication capability and information access regardless of location. Mobile ad hoc networks, that manage it without a need to infrastructure networks, as evolved in time, exhibit some challenges to implement as they become more preferable for military, commercial and special purposes. By considering the challenges and expectations of mobile ad hoc networks, we propose an approach called VCL based DSR (VB-DSR), which uses Dynamic Source Routing (DSR) protocol over Virtual Cell Layout (VCL) structure. VCL is a multi-tier cluster-based approach that provides an efficient resource management and network scalability. We implemented Dynamic Source Routing protocol over VCL structure. Proposed approach, VB-DSR, is a cluster-based two level hierarchical scheme. We also enhance the simulation approach proposed by VCL structure, and use it for the evaluation of tactical communication systems. In this approach, the commands entered during the military computer aided exercises are replayed by running a constructive (combat) model which generates mobility, posture and status data for a number of units, then these data are enhanced and drive a simulation which produces the data related to the performance metrics. The evaluated performance of the system shows that VB-DSR approach satisfies the requirements of mobile ad hoc networks.Yüksek LisansM.Sc

Improving broadcast performance in multi-radio multi-channel multi-rate wireless mesh networks.

This thesis addresses the problem of `efficient' broadcast in a multi-radio multi-channel multi-rate wireless mesh network (MR$^2$-MC WMN). In such a MR$^2$-MC WMN, nodes are equipped with multiple radio network interface cards, each tuned to an orthogonal channel, that can dynamically adjust transmission rate by choosing a modulation scheme appropriate for the channel conditions. We choose `broadcast latency', defined as the maximum delay between a packet's network-wide broadcast at the source and its eventual reception at all network nodes, as the `efficiency' metric of broadcast performance. The problem of constructing a broadcast forwarding structure having minimal broadcast latency is referred to as the `minimum-latency-broadcasting' (MLB) problem. While previous research for broadcast in single-radio single-rate wireless networks has highlighted the wireless medium's `\emph{wireless broadcast advantage}' (WBA); little is known regarding how the new features of MR$^2$-MC WMN may be exploited. We study in this thesis how the availability of multiple radio interfaces (tuned to orthogonal channels) at WMN nodes, and WMN's multi-rate transmission capability and WBA, might be exploited to improve the `broadcast latency' performance. We show the MLB problem for MR$^2$-MC WMN to be NP-hard, and resort to heuristics for its solution. We divide the overall problem into two sub-problems, which we address in two separate parts of this thesis. \emph{In the first part of this thesis}, the MLB problem is defined for the case of single-radio single-channel multi-rate WMNs where WMN nodes are equipped with a single radio tuned to a common channel. \emph{In the second part of this thesis}, the MLB problem is defined for MR$^2$-MC WMNs where WMN nodes are equipped with multiple radios tuned to multiple orthogonal channels. We demonstrate that broadcasting in multi-rate WMNs is significantly different to broadcasting in single-rate WMNs, and that broadcast performance in multi-rate WMNs can be significantly improved by exploiting the availability of multi-rate feature and multiple interfaces. We also present two alternative MLB broadcast frameworks and specific algorithms, centralized and distributed, for each framework that can exploit multiple interfaces at a WMN node, and the multi-rate feature and WBA of MR$^2$-MC WMN to return improved `broadcast latency' performance

Plan Projection, Execution, and Learning for Mobile Robot Control

Most state-of-the-art hybrid control systems for mobile robots are decomposed into different layers. While the deliberation layer reasons about the actions required for the robot in order to achieve a given goal, the behavioral layer is designed to enable the robot to quickly react to unforeseen events. This decomposition guarantees a safe operation even in the presence of unforeseen and dynamic obstacles and enables the robot to cope with situations it was not explicitly programmed for. The layered design, however, also leaves us with the problem of plan execution. The problem of plan execution is the problem of arbitrating between the deliberation- and the behavioral layer. Abstract symbolic actions have to be translated into streams of local control commands. Simultaneously, execution failures have to be handled on an appropriate level of abstraction. It is now widely accepted that plan execution should form a third layer of a hybrid robot control system. The resulting layered architectures are called three-tiered architectures, or 3T architectures for short. Although many high level programming frameworks have been proposed to support the implementation of the intermediate layer, there is no generally accepted algorithmic basis for plan execution in three-tiered architectures. In this thesis, we propose to base plan execution on plan projection and learning and present a general framework for the self-supervised improvement of plan execution. This framework has been implemented in APPEAL, an Architecture for Plan Projection, Execution And Learning, which extends the well known RHINO control system by introducing an execution layer. This thesis contributes to the field of plan-based mobile robot control which investigates the interrelation between planning, reasoning, and learning techniques based on an explicit representation of the robot's intended course of action, a plan. In McDermott's terminology, a plan is that part of a robot control program, which the robot cannot only execute, but also reason about and manipulate. According to that broad view, a plan may serve many purposes in a robot control system like reasoning about future behavior, the revision of intended activities, or learning. In this thesis, plan-based control is applied to the self-supervised improvement of mobile robot plan execution

A ciência da leitura e a produção acadêmica: caminhos trilhados

Linguistics focuses on the different phenomena of language. In macrolinguistics areas, there is Psycholinguistics. This subfield researches (de)coding processes of messages with verbal codes. Thus, one of its influential fields of activity is reading. Reading is one of the most complex information processing tasks. It begins with the graphemes decoding and it finishes with the text comprehension. Regarding the assessment of reading, there are several exams and large-scale tests, such as Pisa, Saeb (Aneb and Anresc/Prova Brasil), ENEM. Alarming statistics come with the indicators from these evaluative instruments. There are, among Brazilians, low levels of reading comprehension and marked functional illiteracy rate. Therefore, this study aimed to research what scientific communication has shared in terms of knowledge about reading. Specifically, the objectives were synthesize, considering the psycholinguistic approach of reading research, studies and research with the most recurrent theme in the reading field evidenced from the electronic communication, in order to investigate the dimensions and limitations of knowledge about this subject. For this, through WebQualis system, Qualis A1 and A2 scientific journals with electronic format and with focuses/scopes related to reading from the areas of (1) Language Arts/Linguistics, (2) Psychology and (3) Education were selected. With the selected journals and through Capes Journals Portal, all their volumes and issues from 2011 to 2015 were analyzed. With this, scientific articles related to reading were mapped. With the mapped articles abstracts, the recurrent themes in reading in the scientific production were observed. Finally, with the full articles that had the recurrent theme, the researches results were integrated, synthesizing and pondering about them. With a critical-reflexive assessment of the data, relevant information was found. First, on one hand, it was noted that the reading has achieved a stable and upward space through the electronic communication. On the other one, it was checked that the contributions of Psychology have a great influence in reading and comprehension research. Second, it was shown that the most frequent theme in electronic productions is comprehension. Finally, with the synthesis, it was found that, increasingly, comprehension topics related to reading neurobiological aspects were empirical and directly investigated. In addition, there are several studies that propose reading teaching methods as well as strategies for improving the comprehension, including the use of TICs. Moreover, it was found that many research results are limited. This is because the comprehension involves several components – cognitive processes and skills. Researches often focus attention on one or the other component of it only, and each research fixes a specific methodology design and that vary considerabably. Regarding the assessment of reading, many of the methodological apparatus tasks evaluate only the product of comprehension and not its process. In other words, built mental representations are evaluated and not how the encoding of this text occurred. Therefore, in short, both the researches advancement in the comprehension field and several limitations were observed.A Linguística atém-se aos mais diferentes fenômenos da língua(gem). Nos domínios macrolinguísticos, há a Psicolinguística. Essa subárea tem como foco de investigação os processos de (de)codificação de mensagens de códigos verbais. Assim, um de seus influentes campos de atuação é o de leitura. A leitura é uma das tarefas de processamento de informações mais complexas. Ela tem como princípio a decodificação grafêmica e como fim a compreensão textual. Em relação à avaliação da leitura, existem diversos testes e provas em larga escala, como o Pisa, o Saeb (Aneb e Anresc/Prova Brasil), o ENEM. Com os indicadores desses instrumentos avaliativos, vêm estatísticas alarmantes. Há, entre os brasileiros, baixos níveis de compreensão leitora e acentuado índice de analfabetismo funcional. Por conseguinte, este trabalho pretendeu investigar o que a comunicação científica tem compartilhado em termos de conhecimento sobre leitura. Especificamente, objetivou-se sintetizar, considerando a abordagem psicolinguística de investigação da leitura, estudos e pesquisas cuja temática evidenciada da comunicação eletrônica fosse a mais recorrente no campo da leitura, a fim de investigar dimensões e limitações do conhecimento a respeito dessa temática. Para isso, selecionaram-se, por meio do sistema WebQualis, periódicos científicos Qualis A1 e A2 em formato eletrônico e com focos/escopos relacionados à leitura, das áreas de (1) Letras/Linguística, (2) Psicologia e (3) Educação. Com os periódicos selecionados e por meio do Portal de Periódicos Capes, analisaram-se todos os seus volumes e números de 2011 a 2015, a fim de mapear artigos científicos com assunto em leitura. Com os resumos dos artigos mapeados, evidenciaram-se temáticas mais recorrentes na produção científica em leitura. Por fim, dos artigos completos cuja temática era a mais recorrente, integraram-se resultados das pesquisas, fazendo-se uma análise, com fins de síntese e reflexão. Da apreciação crítico-reflexiva dos dados, constataram-se relevantes informações. Em primeiro lugar, de um lado, observou-se que a leitura tem conquistado um estável e ascendente espaço em meio à comunicação eletrônica. De outro, demonstrou-se que contribuições da Psicologia têm forte influência na pesquisa de leitura e compreensão. Em segundo, evidenciou-se que a compreensão é a temática mais frequente nas produções eletrônicas. Por fim, com a síntese, constatou-se que, cada vez mais, se investiga empírica e diretamente facetas da compreensão em relação às bases neurobiológicas da leitura. Igualmente, há diversas pesquisas que propõem metodologias de ensino da leitura, bem como estratégias para a melhoria da compreensão, incluindo a utilização das TICs. Além disso, concluiu-se que muitos resultados de pesquisas são limitados. Isso porque a compreensão envolve diversos componentes – processos cognitivos e habilidades. E as pesquisas, muitas vezes, apenas focam a atenção em um ou em outro componente, além de definirem específicos e variados designs de metodologia. Em relação à avaliação da leitura, muitas das tarefas do aparato metodológico das pesquisas apenas avaliam o produto da compreensão e não o seu processo. Ou seja, avaliam-se representações mentais construídas e não como ocorreu a codificação desse texto na mente do leitor. Por conseguinte, em suma, tanto o avanço de pesquisas no campo de compreensão quanto, também, diversas limitações ficaram evidentes

Letters from the War of Ecosystems – An Analysis of Independent Software Vendors in Mobile Application Marketplaces

The recent emergence of a new generation of mobile application marketplaces has changed the business in the mobile ecosystems. The marketplaces have gathered over a million applications by hundreds of thousands of application developers and publishers. Thus, software ecosystems—consisting of developers, consumers and the orchestrator—have emerged as a part of the mobile ecosystem. This dissertation addresses the new challenges faced by mobile application developers in the new ecosystems through empirical methods. By using the theories of two-sided markets and business ecosystems as the basis, the thesis assesses monetization and value creation in the market as well as the impact of electronic Word-of-Mouth (eWOM) and developer multihoming— i. e. contributing for more than one platform—in the ecosystems. The data for the study was collected with web crawling from the three biggest marketplaces: Apple App Store, Google Play and Windows Phone Store. The dissertation consists of six individual articles. The results of the studies show a gap in monetization among the studied applications, while a majority of applications are produced by small or micro-enterprises. The study finds only weak support for the impact of eWOM on the sales of an application in the studied ecosystem. Finally, the study reveals a clear difference in the multi-homing rates between the top application developers and the rest. This has, as discussed in the thesis, an impact on the future market analyses—it seems that the smart device market can sustain several parallel application marketplaces.Muutama vuosi sitten julkistetut uuden sukupolven mobiilisovellusten kauppapaikat ovat muuttaneet mobiiliekosysteemien liiketoimintadynamiikkaa. Nämä uudet markkinapaikat ovat jo onnistuneet houkuttelemaan yli miljoona sovellusta sadoilta tuhansilta ohjelmistokehittäjiltä. Nämä kehittäjät yhdessä markkinapaikan organisoijan sekä loppukäyttäjien kanssa ovat muodostaneet ohjelmistoekosysteemin osaksi laajempaa mobiiliekosysteemiä. Tässä väitöskirjassa tarkastellaan mobiilisovellusten kehittäjien uudenlaisilla kauppapaikoilla kohtaamia haasteita empiiristen tutkimusmenetelmien kautta. Väitöskirjassa arvioidaan sovellusten monetisaatiota ja arvonluontia sekä verkon asiakasarviointien (engl. electronicWord-of-Mouth, eWOM) ja kehittäjien moniliittymisen (engl. multi-homing) — kehittäjä on sitoutunut useammalle kuin yhdelle ekosysteemille — vaikutuksia ekosysteemissä. Työn teoreettinen tausta rakentuu kaksipuolisten markkinapaikkojen ja liiketoimintaekosysteemien päälle. Tutkimuksen aineisto on kerätty kolmelta suurimmalta mobiilisovellusmarkkinapaikalta: Apple App Storesta, Google Playstä ja Windows Phone Storesta. Tämä artikkeliväitöskirja koostuu kuudesta itsenäisestä tutkimuskäsikirjoituksesta. Artikkelien tulokset osoittavat puutteita monetisaatiossa tutkittujen sovellusten joukossa. Merkittävä osa tarkastelluista sovelluksista on pienten yritysten tai yksittäisten kehittäjien julkaisemia. Tutkimuksessa löydettiin vain heikkoa tukea eWOM:in positiiviselle vaikutukselle sovellusten myyntimäärissä. Työssä myös osoitetaan merkittävä ero menestyneimpien sovelluskehittäjien sekä muiden kehittäjien moniliittymiskäyttäytymisen välillä. Tällä havainnolla on merkitystä tuleville markkina-analyyseille ja sen vaikutuksia on käsitelty työssä. Tulokset esimerkiksi viittaavat siihen, että markkinat pystyisivät ylläpitämään useita kilpailevia kauppapaikkoja.Siirretty Doriast