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  • 51.
    Kusetogullari, Hüseyin
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Lavesson, Niklas
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Handwriting image enhancement using local learning windowing, Gaussian Mixture Model and k-means clustering2016Ingår i: 2016 IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2016, Institute of Electrical and Electronics Engineers Inc. , 2016, s. 305-310, artikel-id 7886054Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a new approach is proposed to enhance the handwriting image by using learning-based windowing contrast enhancement and Gaussian Mixture Model (GMM). A fixed size window moves over the handwriting image and two quantitative methods which are discrete entropy (DE) and edge-based contrast measure (EBCM) are used to estimate the quality of each patch. The obtained results are used in the unsupervised learning method by using k-means clustering to assign the quality of handwriting as bad (if it is low contrast) or good (if it is high contrast). After that, if the corresponding patch is estimated as low contrast, a contrast enhancement method is applied to the window to enhance the handwriting. GMM is used as a final step to smoothly exchange information between original and enhanced images to discard the artifacts to represent the final image. The proposed method has been compared with the other contrast enhancement methods for different datasets which are Swedish historical documents, DIBCO2010, DIBCO2012 and DIBCO2013. Results illustrate that proposed method performs well to enhance the handwriting comparing to the existing contrast enhancement methods. © 2016 IEEE.

  • 52. Kusetogullari, Hüseyin
    et al.
    Yavariabdi, Amir
    KTO Karatay University, TUR.
    Cheddad, Abbas
    Grahn, Håkan
    Johan, Hall
    Arkiv Digital, SWE.
    ARDIS: A Swedish Historical Handwritten Digit Dataset2019Ingår i: Neural computing & applications (Print), ISSN 0941-0643, E-ISSN 1433-3058Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper introduces a new image-based handwrittenhistorical digit dataset named ARDIS (Arkiv DigitalSweden). The images in ARDIS dataset are extractedfrom 15,000 Swedish church records which were writtenby different priests with various handwriting styles in thenineteenth and twentieth centuries. The constructed datasetconsists of three single digit datasets and one digit stringsdataset. The digit strings dataset includes 10,000 samplesin Red-Green-Blue (RGB) color space, whereas, the otherdatasets contain 7,600 single digit images in different colorspaces. An extensive analysis of machine learning methodson several digit datasets is examined. Additionally, correlationbetween ARDIS and existing digit datasets ModifiedNational Institute of Standards and Technology (MNIST)and United States Postal Service (USPS) is investigated. Experimental results show that machine learning algorithms,including deep learning methods, provide low recognitionaccuracy as they face difficulties when trained on existingdatasets and tested on ARDIS dataset. Accordingly, ConvolutionalNeural Network (CNN) trained on MNIST andUSPS and tested on ARDIS provide the highest accuracies 58.80% and 35.44%, respectively. Consequently, the resultsreveal that machine learning methods trained on existingdatasets can have difficulties to recognize digits effectivelyon our dataset which proves that ARDIS dataset hasunique characteristics. This dataset is publicly available forthe research community to further advance handwritten digitrecognition algorithms.

  • 53. Kågström, Simon
    et al.
    Grahn, Håkan
    Lundberg, Lars
    Automatic Low Overhead Program Instrumentation with the LOPI framework2005Konferensbidrag (Refereegranskat)
  • 54. Kågström, Simon
    et al.
    Grahn, Håkan
    Lundberg, Lars
    Cibyl: an Environment for Language Diversity on Mobile Devices2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    With an estimated installation base of around 1 billion units, the Java J2ME platform is one of the largest development targets available. For mobile devices, J2ME is often the only available environment. For the very large body of software written in C other languages, this means difficult and costly porting to another language to support J2ME devices. This paper presents the Cibyl programming environment which allows existing code written in C and other languages supported by GCC to be recompiled into Java bytecode and run with close to native Java performance on J2ME devices. Cibyl translates compiled MIPS binaries into Java bytecode. In contrast to other approaches, Cibyl supports the full C language, is based on unmodified standard tools, and does not rely on source code conversion. To achieve good performance, Cibyl employs extensions to the MIPS architecture to support low-overhead calls to native Java functionality and use knowledge of the MIPS ABI to avoid computing unused values and transfer unnecessary registers. An evaluation on multiple virtual machines shows that Cibyl achieves performance similar to native Java, with results ranging from a slowdown of around to a speedup of over 9 depending on the JVM and the benchmark.

  • 55. Kågström, Simon
    et al.
    Grahn, Håkan
    Lundberg, Lars
    Experiences from Implementing Multiprocessor Support for an Industrial Operating System Kernel2005Konferensbidrag (Refereegranskat)
  • 56. Kågström, Simon
    et al.
    Grahn, Håkan
    Lundberg, Lars
    Optimizations in the Cibyl binary translator for J2ME devices2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Java J2ME platform is one of the largest software platforms available, and often the only available development platform for mobile phones, which is a problem when porting C or C++ applications. The Cibyl binary translator targets this problem, translating MIPS binaries into Java bytecode to run on J2ME devices. This paper presents the optimization framework used by Cibyl to provide compact and well-performing translated code. Cibyl optimizes expensive multiplications/divisions, floating point support, function co-location to Java methods and provides a peephole optimizer. The paper also evaluates Cibyl performance both in a real-world GPS navigation application where the optimizations increase display update frequency with around 15% and a comparison against native Java and the NestedVM binary translator where we show that Cibyl can provide significant advantages for common code patterns.

  • 57. Kågström, Simon
    et al.
    Grahn, Håkan
    Lundberg, Lars
    The Design and Implementation of Multiprocessor Support for an Industrial Operating System Kernel2005Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Övergången från singelprocessorsystem till multiprocessorer kräver operativsystemsstöd. I denna rapport beskriver vi designen och implementationen av multiprocessorstödet för en industriell operativsystemskärna. Vi har använt ett jättelås för att skydda kärnan från samtidig åtkomst, vilket tillät oss att implementera stödet utan omfattande källkodsändringar till priset av sämre prestanda. I rapporten diskuterar vi också erfarenheter från implementeringen.

  • 58. Kågström, Simon
    et al.
    Grahn, Håkan
    Lundberg, Lars
    The Design and Implementation of Multiprocessor Support for an Industrial Operating System Kernel2009Ingår i: International Journal of Computers and Their Applications, ISSN 1076-5204, Vol. 16, nr 1, s. 59-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ongoing transition from uniprocessor to multi-core computers requires support from the operating system kernel. Although many general-purpose multiprocessor operating systems exist, there is a large number of specialized operating systems which require porting in order to work on multiprocessors. In this paper we describe the multiprocessor port of a cluster operating system kernel from a producer of industrial systems. Our initial implementation uses a giant locking scheme that serializes kernel execution. We also employed a method in which CPU-local variables are placed in a special section mapped to per-CPU physical memory pages. The giant lock and CPU-local section allowed us to implement an initial working version with only minor changes to the original code, although the giant lock and kernel-bound applications limit the performance of our multiprocessor port. Finally, we also discuss experiences from the implementation.

  • 59. Kågström, Simon
    et al.
    Lundberg, Lars
    Grahn, Håkan
    A novel method for adding multiprocessor support to a large and complex uniprocessor kernel2004Konferensbidrag (Refereegranskat)
    Abstract [en]

    Summary form only given. The current trend of using multiprocessor computers for server applications requires operating system adoptions for high performance. However, modifying large bodies of software is very costly and time-consuming, and the cost of porting an operating system to a multiprocessor might not be motivated by the potential performance benefits. We present a novel method, the application kernel approach, for adaption of an existing uniprocessor kernel to SMP hardware. Our approach considers the existing kernel as a "black box", to which no or small changes are made. Instead, the original kernel runs OS-services unmodified on one processor whereas the other processors execute applications on top of a small custom kernel. A prototype implementation illustrates that the approach can be realized with fairly small resources. We also present an initial performance evaluation where we show that the performance is good for user-bound applications.

  • 60. Kågström, Simon
    et al.
    Lundberg, Lars
    Grahn, Håkan
    The Application Kernel Approach: A Novel Approach for Adding SMP Support to Uniprocessor Operating Systems2006Ingår i: Software - Practice & Experience, ISSN 0038-0644 , Vol. 36, nr 14, s. 1563-1583Artikel i tidskrift (Refereegranskat)
  • 61. Linde, Peter
    et al.
    Grahn, Håkan
    Strategic Publishing Rules – a Manual for Researchers2011Ingår i: ScieCom Info, E-ISSN 1652-3202, Vol. 7, nr 4Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    At Blekinge Institute of Technology (BTH) attempts have been made to with different means motivate researchers to publish in ISI-ranked journals as an adjustment to the resource distribution- and evaluation system of Swedish research policy. This means that we have to stimulate ISI publishing at the same time as we want to meet the research funders’ requirements and make use of the advantages that open access to the research publications of BTH give in the form of increased exposure. The matter is now about finding ways that fulfill both goals. It is unambiguously so that a mere Open Access policy, whether it comes from one’s own higher education institution or from other national research actors, is not sufficient. Particularly not if the policy is in conflict with the established publishing culture among the researchers who not seldom regard the new rules as a counter direction to local and national recommendations to publish in ISI-ranked journals. This is why the Faculty Board at BTH has anchored, supplemented and increased their OA policy document with a descriptive and constructive manual for the individual researcher on how to act to fulfill different conditions and requirements concerning OA generally and research publishing in particular. A policy that does not only provide fundamental support but that also paves the way for administrative systems that give researchers practical support to publish OA and the possibility to choose publishing ways of high quality, favouring both the author and the organization.

  • 62.
    Lundberg, Lars
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Ilie, Dragos
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Melander, Christian
    Compuverde AB.
    Cache Support in a High Performance Fault-Tolerant Distributed Storage System for Cloud and Big Data2015Ingår i: 2015 IEEE 29TH INTERNATIONAL PARALLEL AND DISTRIBUTED PROCESSING SYMPOSIUM WORKSHOPS, IEEE Computer Society, 2015, s. 537-546Konferensbidrag (Refereegranskat)
    Abstract [en]

    Due to the trends towards Big Data and Cloud Computing, one would like to provide large storage systems that are accessible by many servers. A shared storage can, however, become a performance bottleneck and a single-point of failure. Distributed storage systems provide a shared storage to the outside world, but internally they consist of a network of servers and disks, thus avoiding the performance bottleneck and single-point of failure problems. We introduce a cache in a distributed storage system. The cache system must be fault tolerant so that no data is lost in case of a hardware failure. This requirement excludes the use of the common write-invalidate cache consistency protocols. The cache is implemented and evaluated in two steps. The first step focuses on design decisions that improve the performance when only one server uses the same file. In the second step we extend the cache with features that focus on the case when more than one server access the same file. The cache improves the throughput significantly compared to having no cache. The two-step evaluation approach makes it possible to quantify how different design decisions affect the performance of different use cases.

  • 63. Magnusson, Peter S.
    et al.
    Dahlgren, Fredrik
    Grahn, Håkan
    Karlsson, Magnus
    Larsson, Fredrik
    Lundholm, Fredrik
    Moestedt, Andreas
    Nilsson, Jim
    Stenström, Per
    Werner, Bengt
    SimICS/sun4m: A Virtual Workstation1998Konferensbidrag (Refereegranskat)
    Abstract [en]

    System level simulators allow computer architects and system software designers to recreate an accurate and complete replica of the program behavior of a target system, regardless of the availability, existence, or instrumentation support of such a system. Applications include evaluation of architectural design alternatives as well as software engineering tasks such as traditional debugging and performance tuning. We present an implementation of a simulator acting as a virtual workstation fully compatible with the sun4m architecture from Sun Microsystems. Built using the system-level SPARC V8 simulator SimICS, SimICS/sun4m models one or more SPARC V8 processors, supports user-developed modules for data cache and instruction cache simulation and execution profiling of all code, and provides a symbolic and performance debugging environment for operating systems. SimICS/sun4m can boot unmodified operating systems, including Linux 2.0.30 and Solaris 2.6, directly from snapshots of disk partitions. To support essentially arbitrary code, we implemented binary-compatible simulators for several devices, including SCSI, console, interrupt, timers, EEPROM, and Ethernet. The Ethernet simulation hooks into the host and allows the virtual workstation to appear on the local network with full services available (NFS, NIS, rsh, etc). Ethernet and console traffic can be recorded for future playback. The performance of SimICS/sun4m is sufficient to run realistic workloads, such as the database benchmark TPC-D, scaling factor 1/100, or an interactive network application such as Mozilla. The slowdown in relation to native hardware is in the range of 25 to 75 (measured using SPECint95). We also demonstrate some applications, including modeling an 8-processor sun4m version (which does not exist), modeling future memory hierarchies, and debugging an operating system.

  • 64. Mamun, M. A. A.
    et al.
    Khanam, A.
    Grahn, Håkan
    Feldt, Robert
    Comparing Four Static Analysis Tools for Java Concurrency Bugs2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Static analysis (SA) tools are being used for early detection of software defects. Concurrency bugs are different from bugs in sequential programs, and they are often harder to detect. This paper presents the evaluation of four static analysis tools and their capabilities to detect Java concurrency bugs and bug patterns. The tools, i.e., Coverity Prevent, Jtest, FindBugs, and Jlint, are evaluated using concurrent benchmark programs and a collection of multithreaded bug patterns. In addition, we have categorized the bug pattern detectors of the tools and also identified 87 unique bug patterns from the tools’ detectors and literature.

  • 65. Martinsen, Jan Kasper
    et al.
    Grahn, Håkan
    A Methodology for Evaluating JavaScript Execution Behavior in Interactive Web Applications2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    JavaScript has gone from being a mechanism for providing dynamic web pages to an important component of many web applications. Currently one of the most popular type of web applications is so-called social networks, e.g., Facebook, Twitter, and MySpace. However, the workload and execution behavior of JavaScript in this context have not been fully explored or understood. In this paper we present a methodology for characterizing the JavaScript execution behavior in interactive web applications using deterministic execution of use cases. Then, we apply this methodology to evaluate a set of social network applications and compare their behavior to a set of established JavaScript benchmarks. Our results confirm previous studies that the execution behavior of social networks differ from established benchmarks. In addition, we identify one novel difference not published before, i.e., the use of anonymous functions in web applications.

  • 66. Martinsen, Jan Kasper
    et al.
    Grahn, Håkan
    An alternative optimization technique for JavaScript engines2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thread Level Speculation at function level has been suggested as a method to automatically (or semi-automatically) extract parallelism from sequential programs. While there have been multiple implementations in both hardware and software, little work has been done in the context of dynamic programming languages such as JavaScript. In this paper we evaluate the effects of a simple Thread Level Speculation approach, implemented on top of the Rhino1 7R2 JavaScript engine. The evaluation is done using the wellknown JavaScript benchmark suite V8. More specifically, we have measured the effects of our null return value prediction approach for function calls, conflicts with variables in a global scope, and the effects on the execution time. The results show that our strategy to speculate on return values is successful, that conflicts with global variables occur, and for several applications are the execution time improved, while the performance decrease for some applications due to speculation overhead.

  • 67. Martinsen, Jan Kasper
    et al.
    Grahn, Håkan
    Thread-level speculation as an optimization technique in Web Applications Initial results2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Web Applications have become increasingly popular as they allow developers to use an uniform platform for user interactions. The dynamic programming language JavaScript used in most Web Applications has performance penalties, that have been addressed by traditional optimization techniques. We have found that while the performance gain of such techniques are positive for a set of established benchmarks, it often fails to improve the performance of real-life Web Applications. We suggest Thread-Level Speculation (TLS) at the JavaScript function level to automatically extract parallelism to gain performance. There have been multiple TLS proposals in both hardware and software, but little work has been done within JavaScript. Currently we are implementing our TLS ideas in a state-of-the-art JavaScript engine targeted for embedded mobile devices.

  • 68. Martinsen, Jan Kasper
    et al.
    Grahn, Håkan
    Thread-Level Speculation for Web Applications2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thread Level Speculation (TLS) has been suggested as a mean to automatically (or semi-automatically) extract parallelism from sequential programs. While there have been multiple attempts both in hardware and software to implement real time TLS, to the best of our knowledge all attempts have so far been on a byte code level or with statically typed languages. In this study, we examine the potential of TLS for Web Applications, using the popular scripting language JavaScript(JS).We have chosen to execute the programs by traversing their parse trees, taking advantage of information from the programming language that are normally lost when compiled to, e.g., byte code. We have performed a test where we automatically have divided the execution of the parsing tree among 1, 2, 4, and 8 cores for four benchmark programs. We have found that this approach has a small number of rollbacks (i.e. error correction when speculation fails) and significantly increases the performance of our benchmarks.

  • 69. Martinsen, Jan Kasper
    et al.
    Grahn, Håkan
    Isberg, Anders
    A comparative evaluation of JavaScript execution behavior2011Ingår i: Lecture Notes in Computer Science, springer , 2011, Vol. 6757, s. 399-402Konferensbidrag (Refereegranskat)
    Abstract [en]

    JavaScript is a dynamically typed, object-based scripting language with runtime evaluation. It has emerged as an important language for client-side computation of web applications. Previous studies indicate some differences in execution behavior between established benchmarks and real-world web applications. Our study extends previous studies by showing some consequences of these differences. We compare the execution behavior of four application classes, i.e., four JavaScript benchmark suites, the first pages of the Alexa top-100 web sites, 22 use cases for three social networks, and demo applications for the emerging HTML5 standard. Our results indicate that just-in-time compilation often increases the execution time for web applications, and that there are large differences in the execution behavior between benchmarks and web applications at the bytecode level.

  • 70.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Isberg, Anders
    A Limit Study of Thread-Level Speculation in JavaScript Engines --- Initial Results2012Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    JavaScript is a programming language for interactive clientside functionalities in web applications. It is a sequential pro- gramming language, so it cannot take advantage of multicore processors. Previously Thread-Level Speculation has been used to take advantage of multicore processors for JavaScript execution in web applications with promising results execu- tion time wise, but with a large memory overhead. In this study we have evaluated the effects of limiting the amount of memory, the number of threads and the depth of specula- tion in Thread-Level Speculation. Our results indicate that we can tune these parameters to improve execution time and reduce the memory overhead.

  • 71.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Isberg, Anders
    Sony Mobile Communications AB.
    An argument for thread-level speculation and just-in-time compilation in the google's v8 javascript engine2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thread-Level Speculation can be used to take advantage of multicore architectures for web applications. We have implemented Thread-Level Speculation in the state-of-the-art JavaScript engine V8 instead of using an interpreted JavaScript engine. We evaluate the implementation with the Chromium web browser on 15 popular web applications for 2, 4, and 8 cores. The results show that it is benecial to combine Thread-Level Speculation and Just-in-time compi-lation and that it is possible to take advantage of multicore architectures while hiding the details of parallel program-ming from the programmer of web applications.

  • 72.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Isberg, Anders
    Sony Mobile Communications AB Lund, SWE.
    Combining thread-level speculation and just-in-time compilation in Google’s V8 JavaScript engine2017Ingår i: Concurrency and Computation, ISSN 1532-0626, E-ISSN 1532-0634, Vol. 29, nr 1, artikel-id e3826Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Summary: Thread-level speculation can be used to take advantage of multicore architectures for JavaScript in web applications. We extend previous studies with these main contributions; we implement thread-level speculation in the state-of-the art just-in-time-enabled JavaScript engine V8 and make the measurements in the Chromium web browser both from Google instead of using an interpreted JavaScript engine. We evaluate the thread-level speculation and just-in-time compilation combination on 15 very popular web applications, 20 HTML5 demos from the JS1K competition, and 4 Google Maps use cases. The performance is evaluated on two, four, and eight cores. The results clearly show that it is possible to successfully combine thread-level speculation and just-in-time compilation. This makes it possible to take advantage of multicore architectures for web applications while hiding the details of parallel programming from the programmer. Further, our results show an average speedup for the thread-level speculation and just-in-time compilation combination by a factor of almost 3 on four cores and over 4 on eight cores, without changing any of the JavaScript source code.

  • 73. Martinsen, Jan Kasper
    et al.
    Grahn, Håkan
    Isberg, Anders
    Evaluating Four Aspects of JavaScript Execution Behavior in Benchmarks and Web Applications2011Rapport (Övrigt vetenskapligt)
    Abstract [en]

    JavaScript is a dynamically typed and object-based scripting language with runtime evaluation. It has emerged as an important language for client-side computation of web applications. Previous studies have shown differences in behavior between established JavaScript benchmarks and real-world web applications. However, there still remain several important aspects to explore. In this study, we compare the JavaScript execution behavior of four application classes, i.e., four established JavaScript benchmark suites, the first pages of the top 100 sites on the Alexa list, 22 different use cases for Facebook, Twitter, and Blogger, and finally, demo applications for the emerging HTML5 standard. Our results extend previous studies by identifying the importance of anonymous and eval functions, showing that just-in-time compilation often decreases the performance of real-world web applications, and a detailed bytecode instruction mix evaluation.

  • 74.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Isberg, Anders
    Heuristics for Thread-Level Speculation in Web Applications2014Ingår i: IEEE Computer Architecture Letters, ISSN 1556-6056, Vol. 13, nr 2, s. 77-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    JavaScript is a sequential programming language, and Thread-Level Speculation has been proposed to dynamically extract parallelism in order to take advantage of parallel hardware. In previous work, we have showed significant speed-ups with a simple on/off speculation heuristic. In this paper, we propose and evaluate three heuristics for dynamically adapt the speculation: a 2-bit heuristic, an exponential heuristic, and a combination of these two. Our results show that the combined heuristic is able to both increase the number of successful speculations and decrease the execution time for 15 popular web applications.

  • 75.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Isberg, Anders
    Preliminary Results of Combining Thread-Level Speculation and Just-in-Time Compilation in Google’s V82013Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present the first implementation of Thread-Level Speculation in combination with Just-in-time compilation. The implementation is done in Google’s V8, a well-known JavaScript engine, and evaluated on 15 popular web application executing on 2, 4, and 8 core computers. Our results show an average speedup of 2.9 on 4 cores, without any JavaScript code modifications. Further, we have found that the Just-in-time compilation time is significant, and that most functions are lazily compiled (approximately 80%) and that V8 contains features that are advantageous in Thread-Level Speculation.

  • 76. Martinsen, Jan Kasper
    et al.
    Grahn, Håkan
    Isberg, Anders
    The Effect of Thread-Level Speculation on a Set of Well-known Web Applications2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Previous studies have shown that there are large differences between the workload of established JavaScript benchmarks and popular Web Applications. It has also been shown that popular optimization techniques, such as just-in-time compilation, many times degrade the performance of Web Applications. Further, since JavaScript is a sequential language it cannot take advantage of multicore processors. In this paper, we propose to use Thread-Level Speculation (TLS) as an alternative optimization technique for Web Applications written in JavaScript. Our TLS approach is based on speculation at the function level. We have implemented TLS in WebKit, a state-of-the-art web browser and JavaScript engine. Our results show speedups between 2 and 8 on eight cores for seven popular Web Applications, without any JavaScript source code changes at all. The results also show few roll-backs and the additional memory requirements for our speculation is up to 17.8 MB for the studied Web Applications.

  • 77.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Isberg, Anders
    Sony Mobile Communications AB.
    The Effects of Parameter Tuning in Software Thread-Level Speculation in JavaScript Engines2015Ingår i: ACM Transactions on Architecture and Code Optimization, ISSN 1544-3566, Vol. 11, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    JavaScript is a sequential programming language that has a large potential for parallel execution in Web applications. Thread-level speculation can take advantage of this, but it has a large memory overhead. In this article, we evaluate the effects of adjusting various parameters for thread-level speculation. Our results clearly show that thread-level speculation is a useful technique for taking advantage of multicore architectures for JavaScript in Web applications, that nested speculation is required in thread-level speculation, and that the execution characteristics of Web applications significantly reduce the needed memory, the number of threads, and the depth of our speculation.

  • 78.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Isberg, Anders
    Using speculation to enhance JavaScript performance in web applications2013Ingår i: IEEE Internet Computing, ISSN 1089-7801, E-ISSN 1941-0131, Vol. 17, nr 2, s. 10-19Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    JavaScript lets developers provide client-side interactivity in Web applications, but because it is sequential, it can't take advantage of multicore processors. Thread-level speculation (TLS) addresses this issue by enabling the speculation of JavaScript function calls and thus exploits the parallel performance potential multicore processors provide. The authors implemented TLS in the Squirrelfish JavaScript engine, which is part of the WebKit browser environment. They evaluate their approach using 15 popular Web applications on an eight-core computer, and show significant speed-ups without any modifications to the JavaScript source code.

  • 79.
    Martinsen, Jan Kasper
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Isberg, Anders
    Sony Mobile Communications AB.
    Sundström, Henrik
    Sony Mobile Communications AB.
    Reducing Memory in Software-Based Thread-Level Speculation for JavaScript Virtual Machine Execution of Web Applications2014Ingår i: 2014 IEEE INTERNATIONAL CONFERENCE ON HIGH PERFORMANCE COMPUTING AND COMMUNICATIONS, 2014 IEEE 6TH INTL SYMP ON CYBERSPACE SAFETY AND SECURITY, 2014 IEEE 11TH INTL CONF ON EMBEDDED SOFTWARE AND SYST (HPCC,CSS,ICESS), Elsevier, 2014, s. 181-184Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thread-Level Speculation has been used to take advantage of multicore processors in virtual execution environments for the sequential JavaScript scripting language. While the results are promising the memory overhead is high. Here we propose to reduce the memory usage by limiting the checkpoint depth based on an in-depth study of the memory and execution time effects. We also propose an adaptive heuristic to dynamically adjust the checkpoints. We evaluate this using 15 web applications on an 8-core computer. The results show that the memory overhead is reduced for Thread-Level Speculation by over 90% as compared to storing all checkpoints. Further, the performance is often better than when storing all the checkpoints and at worst 4% slower.

  • 80. Mattsson, Michael
    et al.
    Grahn, Håkan
    Mårtensson, Frans
    Software Architecture Evaluation Methods for Performance, Maintainability, Testability, and Portability2006Konferensbidrag (Refereegranskat)
  • 81.
    Muzahim Aziz, Hussein
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Fiedler, Markus
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Grahn, Hakan
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Lundberg, Lars
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Adapting the Streaming Video on the Estimated Motion Position2012Ingår i: Advances in Electrical and Electronic Engineering, ISSN 1336-1376, E-ISSN 1804-3119, Vol. 10, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In real time video streaming, the frames must meet their timing constraints, typically specified as their deadlines. Wireless networks may suffer from bandwidth limitations. To reduce the data transmission over the wireless networks, we propose an adaption technique in the server side by extracting a part of the video frames that considered as a Region Of Interest (ROI), and drop the part outside the ROI from the frames that are between reference frames. The estimated position of the selection of the ROI is computed by using the Sum of Squared Differences (SSD) between consecutive frames. The reconstruction mechanism to the region outside the ROI is implemented in the mobile side by using linear interpolation between reference frames. We evaluate the proposed approach by using Mean Opinion Score (MOS) measurements. MOS are used to evaluate two scenarios with equivalent encoding size, where the users observe the first scenario with low bit rate for the original videos, while for the second scenario the users observe our proposed approach with high bit rate. The results show that our technique significantly reduces the amounts of data are streamed over wireless networks, while the reconstruction mechanism will provides acceptable video quality.

  • 82.
    Muzahim Aziz, Hussein
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Fiedler, Markus
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Lundberg, Lars
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Adapting the Streaming Video Based on the Estimated Position of the Region of Interest2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Streaming real time video over wireless networks cannot guarantee that all the frames could meet their deadlines. Wireless networks may suffer from bandwidth limitations. To reduce the streaming data over wireless networks, we propose a technique to identify, and extract the Region Of Interest (ROI), and drop the non-ROI from the frames that are between the reference frames. The Sum of Absolute Differences (SAD) will compute the consecutive video frames to identify the ROI as it considered the most motion and important region. The reconstruction mechanism to the non-ROI is performed on the mobile side by applying linear interpolation between the reference frames. We evaluate the proposed approach by using Mean Opinion Score (MOS) measurements. MOS are used to evaluate the two scenarios with equivalent encoding size, where the users observe the first scenario with a low bit rate for the original videos, while for the second scenario the users observe our proposed approach. The results show that our technique significantly reduces the amount of data, while the reconstruction mechanism provides acceptable video quality to the mobile viewers.

  • 83.
    Muzahim Aziz, Hussein
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Fiedler, Markus
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Lundberg, Lars
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Distribute the Video Frame Pixels over the Streaming Video Sequence as Sub-Frames2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Real-time video streaming over wireless channel has become an important issue due to the limited bandwidth that is unable to handle the flow of information of the video frames. The characteristics of wireless networks in terms of the available bandwidth, frame delay, and frame losses cannot be known in advance. As the effect of that, the user may notice a frozen picture in the mobile screen. In this work, we propose a technique to prevent freezing frames in the mobile devices based on spatial and temporal locality for the video stream, by splitting the video frame into four sub-frames and combining them with another sub-frames from different sequence positions in the streaming video. In case of frames losses, there is still a possibility that one fourth (one sub-frame) of the frame will be received by the mobile device. The received sub-frames will be reconstructed based on the surrounding pixels. The rate adaptation mechanism will be also highlighted in this work, by skipping sub-frames from the video frames. We show that the server can skip up to 75% of the frame’s pixels and the receiving pixels (sub-frames) can be reconstructed to acceptable quality in the mobile device.

  • 84. Mårtensson, Frans
    et al.
    Grahn, Håkan
    Mattsson, Michael
    An Approach for Performance Evaluation of Software Architectures using Prototyping2003Konferensbidrag (Refereegranskat)
    Abstract [en]

    The fundamental structure of a software system is referred to as the software architecture. Researchers have identified that the quality attributes of a software system, e.g., performance and maintainability, often are restricted by the architecture. Therefore, it is important to evaluate the quality properties of a system already during architectural design. In this paper we propose an approach for evaluating the performance of a software architecture using architectural prototyping. As a part of the approach we have developed an evaluation support framework. We also show the applicability of the approach and evaluate it using a case study of a distributed software system for automated guided vehicles.

  • 85. Mårtensson, Frans
    et al.
    Grahn, Håkan
    Mattsson, Michael
    Evaluating Software Quality Attributes of Communication Components in an Automated Guided Vehicle System2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    The architecture of a large complex software system, i.e., the division of the system into components and modules, is crucial since it often affects and limits the quality attributes of the system, e.g., performance and maintainability. In this paper we evaluate three software components for intra- and inter process communication in a distributed real-time system, i.e., an automated guided vehicle system. We evaluate three quality attributes: performance, maintainability, and portability. The performance and maintainability are evaluated quantitatively using prototype-based evaluation, while the portability is evaluated qualitatively. Our findings indicate that it might be possible to use one third-party component for both intra- and inter process communication, thus replacing two inhouse developed components.

  • 86. Mårtensson, Frans
    et al.
    Jönsson, Per
    Bengtsson, PerOlof
    Grahn, Håkan
    Mattsson, Michael
    A Case Against Continous Simulation for Software Architecture Evaluation2003Konferensbidrag (Refereegranskat)
  • 87.
    Nilsson, Eric
    et al.
    Intel Corp., SWE.
    Aarno, Daniel
    Intel Corp., SWE.
    Carstensen, Erik
    Intel Corp., SWE.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Accelerating Graphics in the Simics Full-System Simulator2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Virtual platforms provide benefits to developers in terms of a more rapid development cycle since development may begin before next-generation hardware is available. However, there is a distinct lack of graphics virtualization in industry-grade virtual platforms, leading to performance issues that may reduce the benefits virtual platforms otherwise have over execution on actual hardware. This paper demonstrates graphics acceleration by the means of paravirtualizing OpenGL ES in the Wind River Simics full-system simulator. We propose a solution for paravirtualized graphics using magic instructions to share memory between target and host systems, and present an implementation utilizing this method. The study illustrates the benefits and drawbacks of paravirtualized graphics acceleration and presents a performance analysis of strengths and weaknesses compared to software rasterization. Additionally, benchmarks are devised to stress key aspects in the solution, such as communication latency and computationally intensive applications. We assess paravirtualization as a viable method to accelerate graphics in system simulators, this reduces frame times up to 34 times compared to that of software rasterization. Furthermore, magic instructions are identified as the primary bottleneck of communication latency in the implementation.

  • 88.
    Nordahl, Christian
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Boeva, Veselka
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Netz Persson, Marie
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Monitoring Household Electricity Consumption Behaviour for Mining Changes2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present an ongoing work on using a household electricity consumption behavior model for recognizing changes in sleep patterns. The work is inspired by recent studies in neuroscience revealing an association between dementia and sleep disorders and more particularly, supporting the hypothesis that insomnia may be a predictor for dementia in older adults. Our approach initially creates a clustering model of normal electricity consumption behavior of the household by using historical data. Then we build a new clustering model on a new set of electricity consumption data collected over a predefined time period and compare the existing model with the built new electricity consumption behavior model. If a discrepancy between the two clustering models is discovered a further analysis of the current electricity consumption behavior is conducted in order to investigate whether this discrepancy is associated with alterations in the resident’s sleep patterns. The approach is studied and initially evaluated on electricity consumption data collected from a single randomly selected anonymous household. The obtained results show that our approach is robust to mining changes in the resident daily routines by monitoring and analyzing their electricity consumption behavior model.

  • 89.
    Nordahl, Christian
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Boeva, Veselka
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Netz Persson, Marie
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datavetenskap.
    Profiling of household residents’ electricity consumption behavior using clustering analysis2019Ingår i: Lect. Notes Comput. Sci., Springer Verlag , 2019, s. 779-786Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study we apply clustering techniques for analyzing and understanding households’ electricity consumption data. The knowledge extracted by this analysis is used to create a model of normal electricity consumption behavior for each particular household. Initially, the household’s electricity consumption data are partitioned into a number of clusters with similar daily electricity consumption profiles. The centroids of the generated clusters can be considered as representative signatures of a household’s electricity consumption behavior. The proposed approach is evaluated by conducting a number of experiments on electricity consumption data of ten selected households. The obtained results show that the proposed approach is suitable for data organizing and understanding, and can be applied for modeling electricity consumption behavior on a household level. © Springer Nature Switzerland AG 2019.

  • 90.
    Nordahl, Christian
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Persson, Marie
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Boeva, Veselka
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Organizing, Visualizing and Understanding Households Electricity Consumption Data through Clustering Analysis.2018Ingår i: Organizing, Visualizing and Understanding Households Electricity Consumption Data through Clustering Analysis, https://sites.google.com/view/arial2018/accepted-papersprogram , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    We propose a cluster analysis approach for organizing, visualizing and understanding households’ electricity consumption data. We initially partition the consumption data into a number of clusters with similar daily electricity consumption profiles. The centroids of each cluster can be seen as representative signatures of a household’s electricity consumption behaviors. We evaluate the proposed approach by conducting a number of experiments on electricity consumption data of ten selected households. Our results show that the approach is suitable for data analysis, understanding and creating electricity consumption behavior models.

  • 91.
    Nordahl, Christian
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Persson, Marie
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Detection of Residents' Abnormal Behaviour by Analysing Energy Consumption of Individual Households2017Ingår i: Proceedings of the 17th IEEE International Conference on Data Mining Workshops (ICDMW) / [ed] Gottumukkala, R; Ning, X; Dong, G; Raghavan, V; Aluru, S; Karypis, G; Miele, L; Wu, X, IEEE, 2017, s. 729-738Konferensbidrag (Refereegranskat)
    Abstract [en]

    As average life expectancy continuously rises, assisting the elderly population with living independently is of great importance. Detecting abnormal behaviour of the elderly living at home is one way to assist the eldercare systems with the increase of the elderly population. In this study, we perform an initial investigation to identify abnormal behaviour of household residents using energy consumption data. We conduct an experiment in two parts, the first to identify a suitable prediction algorithm to model energy consumption behaviour, and the second to detect abnormal behaviour. This approach allows for an initial step for the elderly care that has a low cost, is easily deployable, and is non-intrusive.

  • 92.
    Petersson, Stefan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kreativa teknologier.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Improving image quality by SSIM based increase of run-length zeros in GPGPU JPEG encoding2014Ingår i: Conference Record of the Asilomar Conference on Signals Systems and Computers, IEEE Computer Society, 2014, s. 1714-1718Konferensbidrag (Refereegranskat)
    Abstract [en]

    JPEG encoding is a common technique to compress images. However, since JPEG is a lossy compression certain artifacts may occur in the compressed image. These artifacts typically occur in high frequency or detailed areas of the image. This paper proposes an algorithm based on the SSIM metric to improve the experienced quality in JPEG encoded images. The algorithm improves the quality in detailed areas by up to 1.29 dB while reducing the quality in less detailed areas of the image, thereby increasing the overall experienced quality without increasing the image data size. Further, the algorithm can also be used to decrease the file size (by up to 43%) while preserving the experienced image quality. Finally, an efficient GPU implementation is presented. © 2014 IEEE.

  • 93.
    Petersson, Stefan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kreativa teknologier.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Rasmusson, Jim
    Sony Mobile Communications AB, SWE.
    Color demosaicing using structural instability2016Ingår i: Proceedings - 2016 IEEE International Symposium on Multimedia, ISM 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, s. 541-544Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper introduces a new metric for approximating structural instability in Bayer image data. We show that the metric can be used to identify and classify validity of color correlation in local image regions. The metric is used to improve interpolation performance of an existing state of-the-art single pass linear demosaicing algorithm, with virtually no impact on computational GPGPU complexity and performance. Using four different image sets, the modification is shown to outperform the original method in terms of visual quality, by having an average increase in PSNR of 0.7 dB in the red, 1.5 dB in the green and 0.6 dB in the blue channel respectively. Because of fewer high-frequency artifacts, the average output data size also decreases by 2.5%. © 2016 IEEE.

  • 94.
    Sidorova, Yulia
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Lundberg, Lars
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Rosander, Oliver
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Skold, Lars
    telenor, SWE.
    Recommendations for marketing campaigns in telecommunication business based on the footprint analysis: Who is a good client?2017Ingår i: 2017 8th International Conference on Information, Intelligence, Systems and Applications, IISA 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, s. 513-518Konferensbidrag (Refereegranskat)
    Abstract [en]

    A major investment made by a telecom operator goes into the infrastructure and its maintenance, while business revenues depend on how efficiently it is exploited. We present a data-driven analytic strategy based on combinatorial optimization and analysis of historical data. The data cover historical mobility in one region of Sweden during a week. Applying the proposed method in a case study, we have identified the optimal combination of geodemographic segments in the customer base, developed a functionality to assess the potential of a planned marketing campaign, and investigated how many and which segments to target for customer base growth. A comprehensible summary of the conclusions is created via execution of the queries with a fuzzy logic component. © 2017 IEEE.

  • 95.
    Sidorova, Yulia
    et al.
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Rosander, Oliver
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Sköld, Lars
    Telenor, SWE.
    Grahn, Håkan
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Lundberg, Lars
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för datalogi och datorsystemteknik.
    Finding a healthy equilibrium of geo-demographic segments for a telecom business: Who are malicious hot-spotters?2019Ingår i: Machine Learning Paradigms: Advances in Data Analytics / [ed] George A. Tsihrintzis, Dionisios N. Sotiropoulos, Lakhmi C. Jain, Springer Science and Business Media Deutschland GmbH , 2019, s. 187-196Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    In telecommunication business, a major investment goes into the infrastructure and its maintenance, while business revenues are proportional to how big, good, and well-balanced the customer base is. In our previous work we presented a data-driven analytic strategy based on combinatorial optimization and analysis of the historical mobility designed to quantify the desirability of different geo-demographic segments, and several segments were recommended for a partial reduction. Within a segment, clients are different. In order to enable intelligent reduction, we introduce the term infrastructure-stressing client and, using the proposed method, we reveal the list of the IDs of such clients. We also have developed a visualization tool to allow for manual checks: it shows how the client moved through a sequence of hot spots and was repeatedly served by critically loaded antennas. The code and the footprint matrix are available on the SourceForge. © 2019, Springer International Publishing AG, part of Springer Nature.

  • 96. Stenström, Per
    et al.
    Brorsson, Mats
    Dahlgren, Fredrik
    Grahn, Håkan
    Dubois, Michel
    Boosting the Performance of Shared Memory Multiprocessors1997Ingår i: Computer, ISSN 0018-9162, E-ISSN 1558-0814, Vol. 30, nr 7, s. 63-70Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Shared memory multiprocessors make it practical to convert sequential programs to parallel ones in a variety of applications. An emerging class of shared memory multiprocessors are nonuniform memory access machines with private caches and a cache coherence protocol. Proposed hardware optimizations to CC-NUMA machines can shorten the time processors lose because of cache misses and invalidations. The authors look at cost-performance trade-offs for each of four proposed optimizations: release consistency, adaptive sequential prefetching, migratory sharing detection, and hybrid update/invalidate with a write cache. The four optimizations differ with respect to which application features they attack, what hardware resources they require, and what constraints they impose on the application software. The authors measured the degree of performance improvement using the four optimizations in isolation and in combination, looking at the trade-offs in hardware and programming complexities. Although one combination of the proposed optimizations (prefetching and migratory sharing detection) can boost a sequentially consistent machine to perform as well as a machine with release consistency, release consistency models offer significant performance improvements across a broad application domain at little extra complexity in the machine design. Moreover, a combination of sequential prefetching and hybrid update/invalidate with a write cache cuts the execution time of a sequentially consistent machine by half with fairly modest changes to the second-level cache and the cache protocol. The authors expect that designers will begin to turn more to the release consistency model.

  • 97. Tomaszewski, Piotr
    et al.
    Grahn, Håkan
    Lundberg, Lars
    A Method for an Accurate Early Prediction of Faults in Modified Classes,2006Konferensbidrag (Refereegranskat)
  • 98. Tomaszewski, Piotr
    et al.
    Håkansson, Jim
    Grahn, Håkan
    Lundberg, Lars
    Statistical Models vs. Expert Estimation for Fault Prediction in Modified Code: an Industrial Case Study2007Ingår i: Journal of Systems and Software, ISSN 0164-1212 , Vol. 80, nr 8, s. 1227-1238Artikel i tidskrift (Refereegranskat)
  • 99. Tomaszewski, Piotr
    et al.
    Håkansson, Jim
    Lundberg, Lars
    Grahn, Håkan
    The Accuracy of Fault Prediction in Modified Code –Statistical Model vs. Expert Estimation2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fault prediction models still seem to be more popular in academia than in industry. In industry expert estimations of fault proneness are the most popular methods of deciding where to focus the fault defection efforts. In this paper we present a study in which we empirically evaluate the accuracy of fault prediction offered by statistical models as compared to expert estimations. The study is industry based It involves a large telecommunication system and experts that were involved in the development of this system. Expert estimations are compared to simple prediction models built on another large system, also from the telecommunication domain. We show that the statistical methods clearly outperform the expert estimations. As the main reason for the superiority of the statistical models we see their ability to cope with large datasets, which results in their ability to perform reliable predictions for larger number of components in the system, as well as the ability to perform prediction at a more fine-grain level, e.g., at the class instead of at the component level.

  • 100. Tomaszewski, Piotr
    et al.
    Lundberg, Lars
    Grahn, Håkan
    Improving Fault Detection in Modified Code: A Study from the Telecommunication Industry2007Ingår i: Journal of Computer Science and Technology, ISSN 1000-9000, E-ISSN 1860-4749, Vol. 22, nr 3, s. 397-409Artikel i tidskrift (Refereegranskat)
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