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Book Time Predictable Architectures

Download or read book Time Predictable Architectures written by Christine Rochange and published by John Wiley & Sons. This book was released on 2014-01-17 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: Building computers that can be used to design embedded real-time systems is the subject of this title. Real-time embedded software requires increasingly higher performances. The authors therefore consider processors that implement advanced mechanisms such as pipelining, out-of-order execution, branch prediction, cache memories, multi-threading, multicorearchitectures, etc. The authors of this book investigate the timepredictability of such schemes.

Book High Performance and Time Predictable Embedded Computing

Download or read book High Performance and Time Predictable Embedded Computing written by Pinho, Luis Miguel and published by River Publishers. This book was released on 2018-07-04 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nowadays, the prevalence of computing systems in our lives is so ubiquitous that we live in a cyber-physical world dominated by computer systems, from pacemakers to cars and airplanes. These systems demand for more computational performance to process large amounts of data from multiple data sources with guaranteed processing times. Actuating outside of the required timing bounds may cause the failure of the system, being vital for systems like planes, cars, business monitoring, e-trading, etc. High-Performance and Time-Predictable Embedded Computing presents recent advances in software architecture and tools to support such complex systems, enabling the design of embedded computing devices which are able to deliver high-performance whilst guaranteeing the application required timing bounds. Technical topics discussed in the book include: Parallel embedded platformsProgramming modelsMapping and scheduling of parallel computationsTiming and schedulability analysisRuntimes and operating systems The work reflected in this book was done in the scope of the European project P‑SOCRATES, funded under the FP7 framework program of the European Commission. High-performance and time-predictable embedded computing is ideal for personnel in computer/communication/embedded industries as well as academic staff and master/research students in computer science, embedded systems, cyber-physical systems and internet-of-things.

Book Hard Real Time Computing Systems

Download or read book Hard Real Time Computing Systems written by Giorgio C Buttazzo and published by Springer Science & Business Media. This book was released on 2011-09-10 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: This updated edition offers an indispensable exposition on real-time computing, with particular emphasis on predictable scheduling algorithms. It introduces the fundamental concepts of real-time computing, demonstrates the most significant results in the field, and provides the essential methodologies for designing predictable computing systems used to support time-critical control applications. Along with an in-depth guide to the available approaches for the implementation and analysis of real-time applications, this revised edition contains a close examination of recent developments in real-time systems, including limited preemptive scheduling, resource reservation techniques, overload handling algorithms, and adaptive scheduling techniques. This volume serves as a fundamental advanced-level textbook. Each chapter provides basic concepts, which are followed by algorithms, illustrated with concrete examples, figures and tables. Exercises and solutions are provided to enhance self-study, making this an excellent reference for those interested in real-time computing for designing and/or developing predictable control applications.

Book Software Technologies for Embedded and Ubiquitous Systems

Download or read book Software Technologies for Embedded and Ubiquitous Systems written by Uwe Brinkschulte and published by Springer Science & Business Media. This book was released on 2008-09-19 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book includes selected papers of the 6th IFIP WG 10.2 International Workshop on Software Technologies for Future Embedded and Ubiquitous Systems, SEUS 2008, held on Capri, Italy, in October 2008. The 38 revised full papers presented were carefully reviewed and selected. The papers are organized in topical sections on model-driven development; middleware; real time; quality of service and performance; applications; pervasive and mobile systems: wireless embedded systems; synthesis, verification and protection.

Book Building Evolutionary Architectures

Download or read book Building Evolutionary Architectures written by Neal Ford and published by "O'Reilly Media, Inc.". This book was released on 2022-11-22 with total page 275 pages. Available in PDF, EPUB and Kindle. Book excerpt: The software development ecosystem is constantly changing, providing a constant stream of new tools, frameworks, techniques, and paradigms. Over the past few years, incremental developments in core engineering practices for software development have created the foundations for rethinking how architecture changes over time, along with ways to protect important architectural characteristics as it evolves. This practical guide ties those parts together with a new way to think about architecture and time.

Book Embedded  Cyber Physical  and IoT Systems

Download or read book Embedded Cyber Physical and IoT Systems written by Shuvra S. Bhattacharyya and published by Springer. This book was released on 2019-06-29 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Festschrift is in honor of Marilyn Wolf, on the occasion of her 60th birthday. Prof. Wolf is a renowned researcher and educator in Electrical and Computer Engineering, who has made pioneering contributions in all of the major areas in Embedded, Cyber-Physical, and Internet of Things (IoT) Systems. This book provides a timely collection of contributions that cover important topics related to Smart Cameras, Hardware/Software Co-Design, and Multimedia applications. Embedded systems are everywhere; cyber-physical systems enable monitoring and control of complex physical processes with computers; and IoT technology is of increasing relevance in major application areas, including factory automation, and smart cities. Smart cameras and multimedia technologies introduce novel opportunities and challenges in embedded, cyber-physical and IoT applications. Advanced hardware/software co-design methodologies provide valuable concepts and tools for addressing these challenges. The diverse topics of the chapters in this Festschrift help to reflect the great breadth and depth of Marilyn Wolf's contributions in research and education. The chapters have been written by some of Marilyn’s closest collaborators and colleagues.

Book Architecture of Computing Systems     ARCS 2018

Download or read book Architecture of Computing Systems ARCS 2018 written by Mladen Berekovic and published by Springer. This book was released on 2018-04-05 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the proceedings of the 31st International Conference on Architecture of Computing Systems, ARCS 2018, held in Braunschweig, Germany, in April 2018. The 23 full papers presented in this volume were carefully reviewed and selected from 53 submissions. ARCS has always been a conference attracting leading-edge research outcomes in Computer Architecture and Operating Systems, including a wide spectrum of topics ranging from embedded and real-time systems all the way to large-scale and parallel systems.

Book Scheduling Real Time Streaming Applications onto an Embedded Multiprocessor

Download or read book Scheduling Real Time Streaming Applications onto an Embedded Multiprocessor written by Orlando Moreira and published by Springer Science & Business Media. This book was released on 2013-11-20 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive overview of the state-of-the-art, data flow-based techniques for the analysis, modeling and mapping technologies of concurrent applications on multi-processors. The authors present a flow for designing embedded hard/firm real-time multiprocessor streaming applications, based on data flow formalisms, with a particular focus on wireless modem applications. Architectures are described for the design tools and run-time scheduling and resource management of such a platform.

Book Invasive Computing for Mapping Parallel Programs to Many Core Architectures

Download or read book Invasive Computing for Mapping Parallel Programs to Many Core Architectures written by Andreas Weichslgartner and published by Springer. This book was released on 2017-12-29 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an overview of and essential insights on invasive computing. Pursuing a comprehensive approach, it addresses proper concepts, invasive language constructs, and the principles of invasive hardware. The main focus is on the important topic of how to map task-parallel applications to future multi-core architectures including 1,000 or more processor units. A special focus today is the question of how applications can be mapped onto such architectures while not only taking into account functional correctness, but also non-functional execution properties such as execution times and security properties. The book provides extensive experimental evaluations, investigating the benefits of applying invasive computing and hybrid application mapping to give guarantees on non-functional properties such as timing, energy, and security. The techniques in this book are presented in a step-by-step manner, supported by examples and figures. All proposed ideas for providing guarantees on performance, energy consumption, and security are enabled by using the concept of invasive computing and the exclusive usage of resources.

Book Architecture of Computing Systems     ARCS 2015

Download or read book Architecture of Computing Systems ARCS 2015 written by Luís Miguel Pinho Pinho and published by Springer. This book was released on 2015-03-10 with total page 255 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the proceedings of the 28th International Conference on Architecture of Computing Systems, ARCS 2015, held in Porto, Portugal, in March 2015. The 19 papers presented together with three invited papers were carefully reviewed and selected from 45 submissions. The papers are organized in six sessions covering the topics: hardware, design, applications, trust and privacy, real-time issues and a best papers session.

Book Beyond Databases  Architectures and Structures  Facing the Challenges of Data Proliferation and Growing Variety

Download or read book Beyond Databases Architectures and Structures Facing the Challenges of Data Proliferation and Growing Variety written by Stanisław Kozielski and published by Springer. This book was released on 2018-09-07 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the 14th International Conference entitled Beyond Databases, Architectures and Structures, BDAS 2018, held in Poznań, Poland, in September 2018, during the IFIP World Computer Congress. It consists of 38 carefully reviewed papers selected from 102 submissions. The papers are organized in topical sections, namely big data and cloud computing; architectures, structures and algorithms for efficient data processing; artificial intelligence, data mining and knowledge discovery; text mining, natural language processing, ontologies and semantic web; image analysis and multimedia mining.

Book Architecture of Computing Systems    ARCS 2013

Download or read book Architecture of Computing Systems ARCS 2013 written by Hana Kubatova and published by Springer. This book was released on 2013-02-12 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the 26th International Conference on Architecture of Computing Systems, ARCS 2013, held in Prague, Czech Republic, in February 2013. The 29 papers presented were carefully reviewed and selected from 73 submissions. The topics covered are computer architecture topics such as multi-cores, memory systems, and parallel computing, adaptive system architectures such as reconfigurable systems in hardware and software, customization and application specific accelerators in heterogeneous architectures, organic and autonomic computing including both theoretical and practical results on self-organization, self-configuration, self-optimization, self-healing, and self-protection techniques, operating systems including but not limited to scheduling, memory management, power management, RTOS, energy-awareness, and green computing.

Book Multithreaded Computer Architecture  A Summary of the State of the ART

Download or read book Multithreaded Computer Architecture A Summary of the State of the ART written by Robert A. Iannucci and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 411 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multithreaded computer architecture has emerged as one of the most promising and exciting avenues for the exploitation of parallelism. This new field represents the confluence of several independent research directions which have united over a common set of issues and techniques. Multithreading draws on recent advances in dataflow, RISC, compiling for fine-grained parallel execution, and dynamic resource management. It offers the hope of dramatic performance increases through parallel execution for a broad spectrum of significant applications based on extensions to `traditional' approaches. Multithreaded Computer Architecture is divided into four parts, reflecting four major perspectives on the topic. Part I provides the reader with basic background information, definitions, and surveys of work which have in one way or another been pivotal in defining and shaping multithreading as an architectural discipline. Part II examines key elements of multithreading, highlighting the fundamental nature of latency and synchronization. This section presents clever techniques for hiding latency and supporting large synchronization name spaces. Part III looks at three major multithreaded systems, considering issues of machine organization and compilation strategy. Part IV concludes the volume with an analysis of multithreaded architectures, showcasing methodologies and actual measurements. Multithreaded Computer Architecture: A Summary of the State of the Art is an excellent reference source and may be used as a text for advanced courses on the subject.

Book The Compiler Design Handbook

Download or read book The Compiler Design Handbook written by Y.N. Srikant and published by CRC Press. This book was released on 2018-10-03 with total page 784 pages. Available in PDF, EPUB and Kindle. Book excerpt: Today’s embedded devices and sensor networks are becoming more and more sophisticated, requiring more efficient and highly flexible compilers. Engineers are discovering that many of the compilers in use today are ill-suited to meet the demands of more advanced computer architectures. Updated to include the latest techniques, The Compiler Design Handbook, Second Edition offers a unique opportunity for designers and researchers to update their knowledge, refine their skills, and prepare for emerging innovations. The completely revised handbook includes 14 new chapters addressing topics such as worst case execution time estimation, garbage collection, and energy aware compilation. The editors take special care to consider the growing proliferation of embedded devices, as well as the need for efficient techniques to debug faulty code. New contributors provide additional insight to chapters on register allocation, software pipelining, instruction scheduling, and type systems. Written by top researchers and designers from around the world, The Compiler Design Handbook, Second Edition gives designers the opportunity to incorporate and develop innovative techniques for optimization and code generation.

Book Architecture of Computing Systems   ARCS 2008

Download or read book Architecture of Computing Systems ARCS 2008 written by Theo Ungerer and published by Springer. This book was released on 2008-02-15 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the refereed proceedings of the 21st International Conference on Architecture of Computing Systems, ARCS 2008, held in Dresden, Germany, in February 2008. The 19 revised full papers presented together with 2 keynote papers were carefully reviewed and selected from 47 submissions. The papers cover a wide spectrum reaching from pre-fabrication adaptation of architectural templates to dynamic run-time adaptation of deployed systems with special focus on adaptivity and adaptive system architectures. The papers are organized in topical sections on hardware design, pervasive computing, network processors and memory management, reconfigurable hardware, real-time architectures, organic computing, and computer architecture.

Book Software Technologies for Embedded and Ubiquitous Systems

Download or read book Software Technologies for Embedded and Ubiquitous Systems written by Sunggu Lee and published by Springer Science & Business Media. This book was released on 2009-11-03 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 7th IFIP Workshop on Software Technologies for Future Embedded and Ubiquitous Systems (SEUS) followed on the success of six previous editions in Capri, Italy (2008), Santorini, Greece (2007), Gyeongju, Korea (2006), Seattle, USA (2005), Vienna, Austria (2004), and Hokodate, Japan (2003), establishing SEUS as one of the emerging workshops in the ?eld of embedded and ubiq- tous systems. SEUS 2009 continued the tradition of fostering cross-community scienti?c excellence and establishing strong links between researchand industry. The ?elds of both embedded computing and ubiquitous systems have seen considerable growth over the past few years. Given the advances in these ?elds, and also those in the areas of distributed computing, sensor networks, midd- ware, etc. , the area of ubiquitous embedded computing is now being envisioned as the wayof the future. The systems and technologies that will arise in support of ubiquitous embedded computing will undoubtedly need to address a variety of issues, including dependability, real-time, human–computer interaction, - tonomy, resource constraints, etc. All of these requirements pose a challenge to the research community. The purpose of SEUS 2009 was to bring together - searchersand practitioners with an interest in advancing the state of the artand the state of practice in this emerging ?eld, with the hope of fostering new ideas, collaborations and technologies. SEUS 2009 would not have been possible without the e?ort of many people.

Book Real Time Systems

    Book Details:
  • Author : Hermann Kopetz
  • Publisher : Springer Science & Business Media
  • Release : 2006-04-18
  • ISBN : 0306470551
  • Pages : 347 pages

Download or read book Real Time Systems written by Hermann Kopetz and published by Springer Science & Business Media. This book was released on 2006-04-18 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: 7. 6 Performance Comparison: ET versus TT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 7. 7 The Physical Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 Points to Remember . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 Bibliographic Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Review Questions and Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 Chapter 8: The Time-Triggered Protocols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 8. 1 Introduction to Time-Triggered Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 8. 2 Overview of the TTP/C Protocol Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 8. 3 TheBasic CNI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 Internal Operation of TTP/C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 8. 4 8. 5 TTP/A for Field Bus Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 Points to Remember. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 Bibliographic Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 Review Questions and Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 Chapter 9: Input/Output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 9. 1 The Dual Role of Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 9. 2 Agreement Protocol. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 9. 3 Sampling and Polling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 9. 4 Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201 9. 5 Sensors and Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 9. 6 Physical Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 Points to Remember. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 Bibliographic Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 Review Questions and Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 Chapter 10: Real-Time Operating Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 10. 1 Task Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212 10. 2 Interprocess Communication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 10. 3 Time Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 10. 4 Error Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 10. 5 A Case Study: ERCOS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 Points to Remember. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 Bibliographic Notes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 Review Questions and Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224 Chapter 11: Real-Time Scheduling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 11. 1 The Scheduling Problem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 11. 2 The Adversary Argument. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 11. 3 Dynamic Scheduling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 x TABLE OF CONTENTS 11. 4 Static Scheduling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237 Points to Remember. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Bibliographic Notes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 Review Questions and Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 Chapter 12: Validation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 12. 1 Building aConvincing Safety Case. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 12. 2 Formal Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 12. 3 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .