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<a class="dropdown-item" tabindex="-1" href="ParallelDistributedOverview.html#"><b>Chapter 1</b></a>
<a class="dropdown-item" href="IntroConcSysOverview.html">&nbsp;&nbsp;&nbsp;1.1. Introduction to Concurrent Systems</a>
<a class="dropdown-item" href="SysAndModels.html">&nbsp;&nbsp;&nbsp;1.2. Systems and Models</a>
<a class="dropdown-item" href="Themes.html">&nbsp;&nbsp;&nbsp;1.3. Themes and Guiding Principles</a>
<a class="dropdown-item" href="Architectures.html">&nbsp;&nbsp;&nbsp;1.4. System Architectures</a>
<a class="dropdown-item" href="StateModels.html">&nbsp;&nbsp;&nbsp;1.5. State Models in UML</a>
<a class="dropdown-item" href="SequenceModels.html">&nbsp;&nbsp;&nbsp;1.6. Sequence Models in UML</a>
<a class="dropdown-item" href="StateModelImplementation.html">&nbsp;&nbsp;&nbsp;1.7. Extended Example: State Model Implementation</a>
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<a class="dropdown-item disabled"><b>Chapter 2</b></a>
<a class="dropdown-item" href="ProcessesOverview.html">&nbsp;&nbsp;&nbsp;2.1. Processes and OS Basics</a>
<a class="dropdown-item" href="Multiprogramming.html">&nbsp;&nbsp;&nbsp;2.2. Processes and Multiprogramming</a>
<a class="dropdown-item" href="KernelMechanics.html">&nbsp;&nbsp;&nbsp;2.3. Kernel Mechanics</a>
<a class="dropdown-item" href="Syscall.html">&nbsp;&nbsp;&nbsp;2.4. System Call Interface</a>
<a class="dropdown-item" href="ProcessCycle.html">&nbsp;&nbsp;&nbsp;2.5. Process Life Cycle</a>
<a class="dropdown-item" href="UnixFile.html">&nbsp;&nbsp;&nbsp;2.6. The UNIX File Abstraction</a>
<a class="dropdown-item" href="EventsSignals.html">&nbsp;&nbsp;&nbsp;2.7. Events and Signals</a>
<a class="dropdown-item" href="Extended2Processes.html">&nbsp;&nbsp;&nbsp;2.8. Extended Example: Listing Files with Processes</a>
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<a class="dropdown-item" href="IPCOverview.html">&nbsp;&nbsp;&nbsp;3.1. Concurrency with IPC</a>
<a class="dropdown-item" href="IPCModels.html">&nbsp;&nbsp;&nbsp;3.2. IPC Models</a>
<a class="dropdown-item" href="Pipes.html">&nbsp;&nbsp;&nbsp;3.3. Pipes and FIFOs</a>
<a class="dropdown-item" href="MMap.html">&nbsp;&nbsp;&nbsp;3.4. Shared Memory With Memory-mapped Files</a>
<a class="dropdown-item" href="POSIXvSysV.html">&nbsp;&nbsp;&nbsp;3.5. POSIX vs. System V IPC</a>
<a class="dropdown-item" href="MQueues.html">&nbsp;&nbsp;&nbsp;3.6. Message Passing With Message Queues</a>
<a class="dropdown-item" href="ShMem.html">&nbsp;&nbsp;&nbsp;3.7. Shared Memory</a>
<a class="dropdown-item" href="IPCSems.html">&nbsp;&nbsp;&nbsp;3.8. Semaphores</a>
<a class="dropdown-item" href="Extended3Bash.html">&nbsp;&nbsp;&nbsp;3.9. Extended Example: Bash-lite: A Simple Command-line Shell</a>
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<a class="dropdown-item" href="SocketsOverview.html">&nbsp;&nbsp;&nbsp;4.1. Networked Concurrency</a>
<a class="dropdown-item" href="FiveLayer.html">&nbsp;&nbsp;&nbsp;4.2. The TCP/IP Internet Model</a>
<a class="dropdown-item" href="NetApps.html">&nbsp;&nbsp;&nbsp;4.3. Network Applications and Protocols</a>
<a class="dropdown-item" href="Sockets.html">&nbsp;&nbsp;&nbsp;4.4. The Socket Interface</a>
<a class="dropdown-item" href="TCPSockets.html">&nbsp;&nbsp;&nbsp;4.5. TCP Socket Programming: HTTP</a>
<a class="dropdown-item" href="UDPSockets.html">&nbsp;&nbsp;&nbsp;4.6. UDP Socket Programming: DNS</a>
<a class="dropdown-item" href="AppBroadcast.html">&nbsp;&nbsp;&nbsp;4.7. Application-Layer Broadcasting: DHCP</a>
<a class="dropdown-item" href="Extended4CGI.html">&nbsp;&nbsp;&nbsp;4.8. Extended Example: CGI Web Server</a>
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<a class="dropdown-item disabled"><b>Chapter 5</b></a>
<a class="dropdown-item" href="InternetOverview.html">&nbsp;&nbsp;&nbsp;5.1. The Internet and Connectivity</a>
<a class="dropdown-item" href="AppLayer.html">&nbsp;&nbsp;&nbsp;5.2. Application Layer: Overlay Networks</a>
<a class="dropdown-item" href="TransLayer.html">&nbsp;&nbsp;&nbsp;5.3. Transport Layer</a>
<a class="dropdown-item" href="NetSec.html">&nbsp;&nbsp;&nbsp;5.4. Network Security Fundamentals</a>
<a class="dropdown-item" href="NetLayer.html">&nbsp;&nbsp;&nbsp;5.5. Network Layer: IP</a>
<a class="dropdown-item" href="LinkLayer.html">&nbsp;&nbsp;&nbsp;5.6. Link Layer</a>
<a class="dropdown-item" href="Wireless.html">&nbsp;&nbsp;&nbsp;5.7. Wireless Connectivity: Wi-Fi, Bluetooth, and Zigbee</a>
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<a class="dropdown-item" href="ThreadsOverview.html">&nbsp;&nbsp;&nbsp;6.1. Concurrency with Multithreading</a>
<a class="dropdown-item" href="ProcVThreads.html">&nbsp;&nbsp;&nbsp;6.2. Processes vs. Threads</a>
<a class="dropdown-item" href="RaceConditions.html">&nbsp;&nbsp;&nbsp;6.3. Race Conditions and Critical Sections</a>
<a class="dropdown-item" href="POSIXThreads.html">&nbsp;&nbsp;&nbsp;6.4. POSIX Thread Library</a>
<a class="dropdown-item" href="ThreadArgs.html">&nbsp;&nbsp;&nbsp;6.5. Thread Arguments and Return Values</a>
<a class="dropdown-item" href="ImplicitThreads.html">&nbsp;&nbsp;&nbsp;6.6. Implicit Threading and Language-based Threads</a>
<a class="dropdown-item" href="Extended6Input.html">&nbsp;&nbsp;&nbsp;6.7. Extended Example: Keyboard Input Listener</a>
<a class="dropdown-item" href="Extended6Primes.html">&nbsp;&nbsp;&nbsp;6.8. Extended Example: Concurrent Prime Number Search</a>
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<a class="dropdown-item" href="SynchOverview.html">&nbsp;&nbsp;&nbsp;7.1. Synchronization Primitives</a>
<a class="dropdown-item" href="CritSect.html">&nbsp;&nbsp;&nbsp;7.2. Critical Sections and Peterson's Solution</a>
<a class="dropdown-item" href="Locks.html">&nbsp;&nbsp;&nbsp;7.3. Locks</a>
<a class="dropdown-item" href="Semaphores.html">&nbsp;&nbsp;&nbsp;7.4. Semaphores</a>
<a class="dropdown-item" href="Barriers.html">&nbsp;&nbsp;&nbsp;7.5. Barriers</a>
<a class="dropdown-item" href="Condvars.html">&nbsp;&nbsp;&nbsp;7.6. Condition Variables</a>
<a class="dropdown-item" href="Deadlock.html">&nbsp;&nbsp;&nbsp;7.7. Deadlock</a>
<a class="dropdown-item" href="Extended7Events.html">&nbsp;&nbsp;&nbsp;7.8. Extended Example: Event Log File</a>
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<a class="dropdown-item" href="SynchProblemsOverview.html">&nbsp;&nbsp;&nbsp;8.1. Synchronization Patterns and Problems</a>
<a class="dropdown-item" href="SynchDesign.html">&nbsp;&nbsp;&nbsp;8.2. Basic Synchronization Design Patterns</a>
<a class="dropdown-item" href="ProdCons.html">&nbsp;&nbsp;&nbsp;8.3. Producer-Consumer Problem</a>
<a class="dropdown-item" href="ReadWrite.html">&nbsp;&nbsp;&nbsp;8.4. Readers-Writers Problem</a>
<a class="dropdown-item" href="DiningPhil.html">&nbsp;&nbsp;&nbsp;8.5. Dining Philosophers Problem and Deadlock</a>
<a class="dropdown-item" href="CigSmokers.html">&nbsp;&nbsp;&nbsp;8.6. Cigarette Smokers Problem and the Limits of Semaphores and Locks</a>
<a class="dropdown-item" href="Extended8ModExp.html">&nbsp;&nbsp;&nbsp;8.7. Extended Example: Parallel Modular Exponentiation</a>
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<a class="dropdown-item disabled"><b>Chapter 9</b></a>
<a class="dropdown-item" href="ParallelDistributedOverview.html">&nbsp;&nbsp;&nbsp;9.1. Parallel and Distributed Systems</a>
<a class="dropdown-item" href="ParVConc.html">&nbsp;&nbsp;&nbsp;9.2. Parallelism vs. Concurrency</a>
<a class="dropdown-item" href="ParallelDesign.html">&nbsp;&nbsp;&nbsp;9.3. Parallel Design Patterns</a>
<a class="dropdown-item" href="Scaling.html">&nbsp;&nbsp;&nbsp;9.4. Limits of Parallelism and Scaling</a>
<a class="dropdown-item" href="DistTiming.html">&nbsp;&nbsp;&nbsp;9.5. Timing in Distributed Environments</a>
<a class="dropdown-item" href="DistDataStorage.html">&nbsp;&nbsp;&nbsp;9.6. Reliable Data Storage and Location</a>
<a class="dropdown-item" href="DistConsensus.html">&nbsp;&nbsp;&nbsp;9.7. Consensus in Distributed Systems</a>
<a class="dropdown-item" href="Extended9Blockchain.html">&nbsp;&nbsp;&nbsp;9.8. Extended Example: Blockchain Proof-of-Work</a>
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<a class="dropdown-item disabled"><b>Appendix A</b></a>
<a class="dropdown-item" href="CLangOverview.html">&nbsp;&nbsp;&nbsp;A.1. C Language Reintroduction</a>
<a class="dropdown-item" href="Debugging.html">&nbsp;&nbsp;&nbsp;A.2. Documentation and Debugging</a>
<a class="dropdown-item" href="BasicTypes.html">&nbsp;&nbsp;&nbsp;A.3. Basic Types and Pointers</a>
<a class="dropdown-item" href="Arrays.html">&nbsp;&nbsp;&nbsp;A.4. Arrays, Structs, Enums, and Type Definitions</a>
<a class="dropdown-item" href="Functions.html">&nbsp;&nbsp;&nbsp;A.5. Functions and Scope</a>
<a class="dropdown-item" href="Pointers.html">&nbsp;&nbsp;&nbsp;A.6. Pointers and Dynamic Allocation</a>
<a class="dropdown-item" href="Strings.html">&nbsp;&nbsp;&nbsp;A.7. Strings</a>
<a class="dropdown-item" href="FunctionPointers.html">&nbsp;&nbsp;&nbsp;A.8. Function Pointers</a>
<a class="dropdown-item" href="Files.html">&nbsp;&nbsp;&nbsp;A.9. Files</a>
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<h1>9.1. Parallel and Distributed Systems<a class="headerlink" href="ParallelDistributedOverview.html#parallel-and-distributed-systems" title="Permalink to this headline"></a></h1>
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<a class="reference internal image-reference" href="_images/CSF-Timeline.9.png"><img class="p-3 mb-2 align-center border border-dark rounded-lg" alt="Timeline of major CSF topics with Parallelism and Distributed Systems highlighted" src="_images/CSF-Timeline.9.png" style="width: 90%;" /></a>
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<blockquote class="blockquote text-center">
<p>“A distributed system is one in which the failure of a computer you didnt
even know existed can render your own computer unusable.”
<footer class="blockquote-footer">Leslie Lamport</footer>
</blockquote><p>As with multithreading, the general concepts of distributed computing are
decades old. The Internet, for instance, can be characterized as a distributed
computing system. Leslie Lamport introduced distributed timestamps in 1978.
However, the past two decades have brought these techniques to new heights with
massively parallel supercomputers (such as Cray Titan or IBM BlueGene) and grid
computing (Berkeley Open Infrastructure for Network Computing (BOINC),
Folding&#64;home, Great Internet Mersenne Prime Search (GIMPS)). Furthermore, the
domains of parallel and distributed computing remain key areas of computer
science research. This chapter provides an introduction to key results and
concepts in these areas, providing a foundation for interested readers to pursue
more advanced study.</p>
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<p class="topic-title first pt-2 mb-1">Chapter Objectives</p><hr class="mt-1" />
<p>In this chapter, we will address the following instructional objectives:</p>
<ul class="simple">
<li>We will distinguish the notions of concurrency and parallelism and examine the
relationship of both techniques to the hardware capabilities.</li>
<li>We will explore parallel design patterns that can be applied toward the
construction of algorithms, program implementations, or program execution.</li>
<li>We will examine the theoretical and practical limits to parallelism.</li>
<li>We will consider three foundational concepts—timing of events, object
location, and consensus—of distributed systems that have been very influential
in this field.</li>
</ul>
</div>
<p>The principles of concurrency and synchronization can apply to a wide variety of
systems. In particular, throughout most of the history of computing, most
systems implemented multiprogramming in the software (the operating system) to
improve utilization on a processor that was capability of one task at a time. In
recent years, there has been an increasing focus on and adoption of hardware
capable of parallel execution units. The ability to exploit parallelism on
modern hardware makes it possible to achieve significant gains in the speed of computing.</p>
<p>The benefits of parallelism, however, are not automatic and unlimited. Creating
software that can take full advantage of hardware support for parallelism
requires careful design and implementation. Some algorithms simply cannot be
executed in parallel; for algorithms that can be parallelized, the code must be
properly structured to account for the nondeterministic nature of the timing
that can arise. Furthermore, even if the algorithm can be parallelized, there
are theoretical and practical limits to how much the speed can be improved. In
this chapter, we will explore these issues, strategies, and limits of parallelism.</p>
<p>In addition to parallelism on a single computer, we can link a larger collection
of <a class="reference internal" href="Glossary.html#term-distributed-system"><span class="xref std std-term">distributed systems</span></a> of independent computers. The goal of distributed
systems is to link many computers together, executing coordinated software to
accomplish a single, larger goal. Distributed computing involves confronting the
challenge of unexpected and intermittent failures of nodes in the system. As an
introduction to this area of computing, we will explore how computer scientists
have addressed three well-known challenges in distributed computing:
communicating the timing of events, achieving an agreement — known as
<a class="reference internal" href="Glossary.html#term-consensus-protocol"><span class="xref std std-term">consensus</span></a> — on the state of the system, and storing data so that it can
still be accessed when nodes fail. Readers who find these topics of interest
should explore the recommended readings at the end of the chapter.</p>
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