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<a class="dropdown-item" tabindex="-1" href="Extended8ModExp.html#"><b>Chapter 1</b></a>
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<a class="dropdown-item" href="IntroConcSysOverview.html"> 1.1. Introduction to Concurrent Systems</a>
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<a class="dropdown-item" href="SysAndModels.html"> 1.2. Systems and Models</a>
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<a class="dropdown-item" href="Themes.html"> 1.3. Themes and Guiding Principles</a>
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<a class="dropdown-item" href="SequenceModels.html"> 1.6. Sequence Models in UML</a>
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<a class="dropdown-item" href="StateModelImplementation.html"> 1.7. Extended Example: State Model Implementation</a>
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<a class="dropdown-item disabled"><b>Chapter 2</b></a>
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<a class="dropdown-item" href="ProcessesOverview.html"> 2.1. Processes and OS Basics</a>
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<a class="dropdown-item" href="Multiprogramming.html"> 2.2. Processes and Multiprogramming</a>
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<a class="dropdown-item" href="Syscall.html"> 2.4. System Call Interface</a>
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<a class="dropdown-item" href="ProcessCycle.html"> 2.5. Process Life Cycle</a>
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<a class="dropdown-item" href="UnixFile.html"> 2.6. The UNIX File Abstraction</a>
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<a class="dropdown-item" href="EventsSignals.html"> 2.7. Events and Signals</a>
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<a class="dropdown-item" href="Extended2Processes.html"> 2.8. Extended Example: Listing Files with Processes</a>
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<a class="dropdown-item disabled"><b>Chapter 3</b></a>
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<a class="dropdown-item" href="IPCOverview.html"> 3.1. Concurrency with IPC</a>
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<a class="dropdown-item" href="IPCModels.html"> 3.2. IPC Models</a>
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<a class="dropdown-item" href="Pipes.html"> 3.3. Pipes and FIFOs</a>
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<a class="dropdown-item" href="MMap.html"> 3.4. Shared Memory With Memory-mapped Files</a>
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<a class="dropdown-item" href="POSIXvSysV.html"> 3.5. POSIX vs. System V IPC</a>
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<a class="dropdown-item" href="MQueues.html"> 3.6. Message Passing With Message Queues</a>
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<a class="dropdown-item" href="ShMem.html"> 3.7. Shared Memory</a>
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<a class="dropdown-item" href="IPCSems.html"> 3.8. Semaphores</a>
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<a class="dropdown-item" href="Extended3Bash.html"> 3.9. Extended Example: Bash-lite: A Simple Command-line Shell</a>
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<a class="dropdown-item disabled"><b>Chapter 4</b></a>
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<a class="dropdown-item" href="SocketsOverview.html"> 4.1. Networked Concurrency</a>
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<a class="dropdown-item" href="FiveLayer.html"> 4.2. The TCP/IP Internet Model</a>
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<a class="dropdown-item" href="NetApps.html"> 4.3. Network Applications and Protocols</a>
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<a class="dropdown-item" href="Sockets.html"> 4.4. The Socket Interface</a>
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<a class="dropdown-item" href="TCPSockets.html"> 4.5. TCP Socket Programming: HTTP</a>
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<a class="dropdown-item" href="UDPSockets.html"> 4.6. UDP Socket Programming: DNS</a>
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<a class="dropdown-item" href="AppBroadcast.html"> 4.7. Application-Layer Broadcasting: DHCP</a>
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<a class="dropdown-item" href="Extended4CGI.html"> 4.8. Extended Example: CGI Web Server</a>
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<a class="dropdown-item disabled"><b>Chapter 5</b></a>
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<a class="dropdown-item" href="InternetOverview.html"> 5.1. The Internet and Connectivity</a>
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<a class="dropdown-item" href="AppLayer.html"> 5.2. Application Layer: Overlay Networks</a>
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<a class="dropdown-item" href="TransLayer.html"> 5.3. Transport Layer</a>
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<a class="dropdown-item" href="NetSec.html"> 5.4. Network Security Fundamentals</a>
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<a class="dropdown-item" href="Wireless.html"> 5.7. Wireless Connectivity: Wi-Fi, Bluetooth, and Zigbee</a>
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<a class="dropdown-item" href="ThreadsOverview.html"> 6.1. Concurrency with Multithreading</a>
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<a class="dropdown-item" href="ProcVThreads.html"> 6.2. Processes vs. Threads</a>
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<a class="dropdown-item" href="RaceConditions.html"> 6.3. Race Conditions and Critical Sections</a>
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<a class="dropdown-item" href="POSIXThreads.html"> 6.4. POSIX Thread Library</a>
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<a class="dropdown-item" href="ThreadArgs.html"> 6.5. Thread Arguments and Return Values</a>
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<a class="dropdown-item" href="ImplicitThreads.html"> 6.6. Implicit Threading and Language-based Threads</a>
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<a class="dropdown-item" href="Extended6Input.html"> 6.7. Extended Example: Keyboard Input Listener</a>
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<a class="dropdown-item" href="Extended6Primes.html"> 6.8. Extended Example: Concurrent Prime Number Search</a>
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<a class="dropdown-item disabled"><b>Chapter 7</b></a>
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<a class="dropdown-item" href="SynchOverview.html"> 7.1. Synchronization Primitives</a>
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<a class="dropdown-item" href="CritSect.html"> 7.2. Critical Sections and Peterson's Solution</a>
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<a class="dropdown-item" href="Locks.html"> 7.3. Locks</a>
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<a class="dropdown-item" href="Semaphores.html"> 7.4. Semaphores</a>
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<a class="dropdown-item" href="Barriers.html"> 7.5. Barriers</a>
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<a class="dropdown-item" href="Deadlock.html"> 7.7. Deadlock</a>
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<a class="dropdown-item" href="Extended7Events.html"> 7.8. Extended Example: Event Log File</a>
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<a class="dropdown-item disabled"><b>Chapter 8</b></a>
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<a class="dropdown-item" href="SynchProblemsOverview.html"> 8.1. Synchronization Patterns and Problems</a>
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<a class="dropdown-item" href="SynchDesign.html"> 8.2. Basic Synchronization Design Patterns</a>
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<a class="dropdown-item" href="ProdCons.html"> 8.3. Producer-Consumer Problem</a>
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<a class="dropdown-item" href="ReadWrite.html"> 8.4. Readers-Writers Problem</a>
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<a class="dropdown-item" href="DiningPhil.html"> 8.5. Dining Philosophers Problem and Deadlock</a>
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<a class="dropdown-item" href="CigSmokers.html"> 8.6. Cigarette Smokers Problem and the Limits of Semaphores and Locks</a>
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<a class="dropdown-item" href="Extended8ModExp.html"> 8.7. Extended Example: Parallel Modular Exponentiation</a>
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<a class="dropdown-item disabled"><b>Chapter 9</b></a>
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<a class="dropdown-item" href="ParallelDistributedOverview.html"> 9.1. Parallel and Distributed Systems</a>
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<a class="dropdown-item" href="ParVConc.html"> 9.2. Parallelism vs. Concurrency</a>
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<a class="dropdown-item" href="ParallelDesign.html"> 9.3. Parallel Design Patterns</a>
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<a class="dropdown-item" href="Scaling.html"> 9.4. Limits of Parallelism and Scaling</a>
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<a class="dropdown-item" href="DistTiming.html"> 9.5. Timing in Distributed Environments</a>
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<a class="dropdown-item" href="DistDataStorage.html"> 9.6. Reliable Data Storage and Location</a>
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<a class="dropdown-item" href="DistConsensus.html"> 9.7. Consensus in Distributed Systems</a>
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<a class="dropdown-item" href="Extended9Blockchain.html"> 9.8. Extended Example: Blockchain Proof-of-Work</a>
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<a class="dropdown-item disabled"><b>Appendix A</b></a>
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<a class="dropdown-item" href="CLangOverview.html"> A.1. C Language Reintroduction</a>
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<a class="dropdown-item" href="Debugging.html"> A.2. Documentation and Debugging</a>
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<a class="dropdown-item" href="BasicTypes.html"> A.3. Basic Types and Pointers</a>
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<a class="dropdown-item" href="Arrays.html"> A.4. Arrays, Structs, Enums, and Type Definitions</a>
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<a class="dropdown-item" href="Functions.html"> A.5. Functions and Scope</a>
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<a class="dropdown-item" href="Pointers.html"> A.6. Pointers and Dynamic Allocation</a>
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<a class="dropdown-item" href="Strings.html"> A.7. Strings</a>
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<a class="dropdown-item" href="Files.html"> A.9. Files</a>
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«  <a id="prevmod" href="CigSmokers.html">8.6. Cigarette Smokers Problem and the Limits of Semaphores and Locks</a>
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<script>ODSA.SETTINGS.DISP_MOD_COMP = true;ODSA.SETTINGS.MODULE_NAME = "Extended8ModExp";ODSA.SETTINGS.MODULE_LONG_NAME = "Extended Example: Parallel Modular Exponentiation";ODSA.SETTINGS.MODULE_CHAPTER = "Synchronization Patterns and Problems"; ODSA.SETTINGS.BUILD_DATE = "2021-06-01 15:31:51"; ODSA.SETTINGS.BUILD_CMAP = false;JSAV_OPTIONS['lang']='en';JSAV_EXERCISE_OPTIONS['code']='java';</script><div class="section" id="extended-example-parallel-modular-exponentiation">
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<h1>8.7. Extended Example: Parallel Modular Exponentiation<a class="headerlink" href="Extended8ModExp.html#extended-example-parallel-modular-exponentiation" title="Permalink to this headline">¶</a></h1>
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<p>Modular exponentiation is a mathematical calculation that is used in a variety
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of applications, including public key cryptography. This operation simply
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consists of performing an integer exponentiation and applying a modulus. For
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instance, 2<sup>3</sup> mod 7 = 8 mod 7 ≡ 1 mod 7. This parallel form makes
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use of the fact that multiplication is associative; if we want to compute
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(2<sup>3</sup> * 5<sup>4</sup> ) mod 7, we can calculate
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2<sup>3</sup> mod 7 and 5<sup>4</sup> mod 7 in parallel, then multiply
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their results together. This form uses an intentionally slow implementation of
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modular exponentiation to illustrate the performance improvement from
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parallelism.</p>
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216</pre></div></td><td class="code"><div class="highlight bg-light"><pre class="mb-0"><span></span><span class="cp">#include</span> <span class="cpf"><assert.h></span><span class="cp"></span>
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<span class="cp">#include</span> <span class="cpf"><inttypes.h></span><span class="cp"></span>
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<span class="cp">#include</span> <span class="cpf"><pthread.h></span><span class="cp"></span>
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<span class="cp">#include</span> <span class="cpf"><semaphore.h></span><span class="cp"></span>
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<span class="cp">#include</span> <span class="cpf"><stdbool.h></span><span class="cp"></span>
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<span class="cp">#include</span> <span class="cpf"><stdio.h></span><span class="cp"></span>
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<span class="cp">#include</span> <span class="cpf"><stdint.h></span><span class="cp"></span>
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<span class="cp">#include</span> <span class="cpf"><stdlib.h></span><span class="cp"></span>
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<span class="cp">#include</span> <span class="cpf"><string.h></span><span class="cp"></span>
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<span class="kt">uint64_t</span> <span class="nf">mod_power</span> <span class="p">(</span><span class="kt">uint64_t</span><span class="p">,</span> <span class="kt">uint64_t</span><span class="p">);</span>
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<span class="kt">void</span> <span class="o">*</span> <span class="nf">mod_power_consumer</span> <span class="p">(</span><span class="kt">void</span> <span class="o">*</span><span class="p">);</span>
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<span class="kt">uint64_t</span> <span class="o">*</span> <span class="nf">randomize_powers</span> <span class="p">(</span><span class="kt">size_t</span><span class="p">,</span> <span class="kt">unsigned</span><span class="p">,</span> <span class="kt">double</span><span class="p">,</span> <span class="kt">size_t</span><span class="p">);</span>
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<span class="cm">/* Can use this to change the queue size */</span>
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<span class="cp">#define QUEUE_SIZE 10</span>
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<span class="cm">/* Synchronization primitives and global result */</span>
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<span class="n">pthread_mutex_t</span> <span class="n">mutex</span><span class="p">;</span>
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<span class="cp">#define SEM_AVAILABLE "/OpenCSF_Available"</span>
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<span class="cp">#define SEM_READY "/OpenCSF_Ready"</span>
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<span class="n">sem_t</span> <span class="o">*</span><span class="n">space_available</span><span class="p">;</span>
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|
<span class="n">sem_t</span> <span class="o">*</span><span class="n">item_ready</span><span class="p">;</span>
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<span class="kt">uint64_t</span> <span class="n">result</span> <span class="o">=</span> <span class="mi">1</span><span class="p">;</span>
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<span class="cm">/* Each entry is for a single base^power computation */</span>
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|
<span class="k">struct</span> <span class="n">queue_entry</span> <span class="p">{</span>
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|
<span class="kt">uint64_t</span> <span class="n">base</span><span class="p">;</span>
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<span class="kt">uint64_t</span> <span class="n">power</span><span class="p">;</span>
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<span class="p">};</span>
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<span class="cm">/* Variables that define the queue structure */</span>
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|
<span class="k">struct</span> <span class="n">queue_entry</span> <span class="n">queue</span><span class="p">[</span><span class="n">QUEUE_SIZE</span><span class="p">];</span>
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|
<span class="kt">size_t</span> <span class="n">next_out</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
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<span class="kt">size_t</span> <span class="n">next_in</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
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<span class="cm">/* Set of 100 primes and the modulus to use for calculations */</span>
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<span class="kt">uint64_t</span> <span class="n">primes</span><span class="p">[]</span> <span class="o">=</span> <span class="p">{</span>
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|
<span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">7</span><span class="p">,</span> <span class="mi">11</span><span class="p">,</span> <span class="mi">13</span><span class="p">,</span> <span class="mi">17</span><span class="p">,</span> <span class="mi">19</span><span class="p">,</span> <span class="mi">23</span><span class="p">,</span> <span class="mi">29</span><span class="p">,</span> <span class="mi">31</span><span class="p">,</span> <span class="mi">37</span><span class="p">,</span> <span class="mi">41</span><span class="p">,</span> <span class="mi">43</span><span class="p">,</span> <span class="mi">47</span><span class="p">,</span> <span class="mi">53</span><span class="p">,</span>
|
|
<span class="mi">59</span><span class="p">,</span> <span class="mi">61</span><span class="p">,</span> <span class="mi">67</span><span class="p">,</span> <span class="mi">71</span><span class="p">,</span> <span class="mi">73</span><span class="p">,</span> <span class="mi">79</span><span class="p">,</span> <span class="mi">83</span><span class="p">,</span> <span class="mi">89</span><span class="p">,</span> <span class="mi">97</span><span class="p">,</span> <span class="mi">101</span><span class="p">,</span> <span class="mi">103</span><span class="p">,</span> <span class="mi">107</span><span class="p">,</span> <span class="mi">109</span><span class="p">,</span> <span class="mi">113</span><span class="p">,</span>
|
|
<span class="mi">127</span><span class="p">,</span> <span class="mi">131</span><span class="p">,</span> <span class="mi">137</span><span class="p">,</span> <span class="mi">139</span><span class="p">,</span> <span class="mi">149</span><span class="p">,</span> <span class="mi">151</span><span class="p">,</span> <span class="mi">157</span><span class="p">,</span> <span class="mi">163</span><span class="p">,</span> <span class="mi">167</span><span class="p">,</span> <span class="mi">173</span><span class="p">,</span> <span class="mi">179</span><span class="p">,</span> <span class="mi">181</span><span class="p">,</span>
|
|
<span class="mi">191</span><span class="p">,</span> <span class="mi">193</span><span class="p">,</span> <span class="mi">197</span><span class="p">,</span> <span class="mi">199</span><span class="p">,</span> <span class="mi">211</span><span class="p">,</span> <span class="mi">223</span><span class="p">,</span> <span class="mi">227</span><span class="p">,</span> <span class="mi">229</span><span class="p">,</span> <span class="mi">233</span><span class="p">,</span> <span class="mi">239</span><span class="p">,</span> <span class="mi">241</span><span class="p">,</span> <span class="mi">251</span><span class="p">,</span>
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|
<span class="mi">257</span><span class="p">,</span> <span class="mi">263</span><span class="p">,</span> <span class="mi">269</span><span class="p">,</span> <span class="mi">271</span><span class="p">,</span> <span class="mi">277</span><span class="p">,</span> <span class="mi">281</span><span class="p">,</span> <span class="mi">283</span><span class="p">,</span> <span class="mi">293</span><span class="p">,</span> <span class="mi">307</span><span class="p">,</span> <span class="mi">311</span><span class="p">,</span> <span class="mi">313</span><span class="p">,</span> <span class="mi">317</span><span class="p">,</span>
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|
<span class="mi">331</span><span class="p">,</span> <span class="mi">337</span><span class="p">,</span> <span class="mi">347</span><span class="p">,</span> <span class="mi">349</span><span class="p">,</span> <span class="mi">353</span><span class="p">,</span> <span class="mi">359</span><span class="p">,</span> <span class="mi">367</span><span class="p">,</span> <span class="mi">373</span><span class="p">,</span> <span class="mi">379</span><span class="p">,</span> <span class="mi">383</span><span class="p">,</span> <span class="mi">389</span><span class="p">,</span> <span class="mi">397</span><span class="p">,</span>
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|
<span class="mi">401</span><span class="p">,</span> <span class="mi">409</span><span class="p">,</span> <span class="mi">419</span><span class="p">,</span> <span class="mi">421</span><span class="p">,</span> <span class="mi">431</span><span class="p">,</span> <span class="mi">433</span><span class="p">,</span> <span class="mi">439</span><span class="p">,</span> <span class="mi">443</span><span class="p">,</span> <span class="mi">449</span><span class="p">,</span> <span class="mi">457</span><span class="p">,</span> <span class="mi">461</span><span class="p">,</span> <span class="mi">463</span><span class="p">,</span>
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|
<span class="mi">467</span><span class="p">,</span> <span class="mi">479</span><span class="p">,</span> <span class="mi">487</span><span class="p">,</span> <span class="mi">491</span><span class="p">,</span> <span class="mi">499</span><span class="p">,</span> <span class="mi">503</span><span class="p">,</span> <span class="mi">509</span><span class="p">,</span> <span class="mi">521</span><span class="p">,</span> <span class="mi">523</span><span class="p">,</span> <span class="mi">541</span>
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|
<span class="p">};</span>
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|
<span class="kt">size_t</span> <span class="n">primes_length</span> <span class="o">=</span> <span class="mi">100</span><span class="p">;</span>
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|
<span class="kt">uint64_t</span> <span class="n">modulus</span> <span class="o">=</span> <span class="mi">524287</span><span class="p">;</span>
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|
|
|
<span class="kt">int</span>
|
|
<span class="nf">main</span> <span class="p">(</span><span class="kt">void</span><span class="p">)</span>
|
|
<span class="p">{</span>
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|
<span class="cm">/* Change these numbers as desired. This set will create 4</span>
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|
<span class="cm"> threads to multiple 50% of the primes, each to a power of</span>
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|
<span class="cm"> at least 10,000. */</span>
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|
<span class="kt">size_t</span> <span class="n">number_of_threads</span> <span class="o">=</span> <span class="mi">4</span><span class="p">;</span>
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|
<span class="kt">unsigned</span> <span class="n">seed</span> <span class="o">=</span> <span class="mi">25</span><span class="p">;</span>
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<span class="kt">double</span> <span class="n">threshold</span> <span class="o">=</span> <span class="mf">0.5</span><span class="p">;</span>
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<span class="kt">size_t</span> <span class="n">minimum</span> <span class="o">=</span> <span class="mi">10000000</span><span class="p">;</span>
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<span class="cm">/* Generate an array of random powers to use */</span>
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|
<span class="kt">uint64_t</span> <span class="o">*</span><span class="n">powers</span> <span class="o">=</span>
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|
<span class="n">randomize_powers</span> <span class="p">(</span><span class="n">primes_length</span><span class="p">,</span> <span class="n">seed</span><span class="p">,</span> <span class="n">threshold</span><span class="p">,</span> <span class="n">minimum</span><span class="p">);</span>
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<span class="cm">/* Initialize synchronization primitives as needed */</span>
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|
<span class="n">pthread_mutex_init</span> <span class="p">(</span><span class="o">&</span><span class="n">mutex</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">);</span>
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|
<span class="n">sem_unlink</span> <span class="p">(</span><span class="n">SEM_AVAILABLE</span><span class="p">);</span> <span class="c1">// Delete an old semaphore instance</span>
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|
<span class="n">sem_unlink</span> <span class="p">(</span><span class="n">SEM_READY</span><span class="p">);</span> <span class="c1">// Delete an old semaphore instance</span>
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|
<span class="n">space_available</span> <span class="o">=</span>
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|
<span class="n">sem_open</span> <span class="p">(</span><span class="n">SEM_AVAILABLE</span><span class="p">,</span> <span class="n">O_CREAT</span> <span class="o">|</span> <span class="n">O_EXCL</span><span class="p">,</span> <span class="n">S_IRUSR</span> <span class="o">|</span> <span class="n">S_IWUSR</span><span class="p">,</span> <span class="n">QUEUE_SIZE</span><span class="p">);</span>
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|
<span class="n">item_ready</span> <span class="o">=</span> <span class="n">sem_open</span> <span class="p">(</span><span class="n">SEM_READY</span><span class="p">,</span> <span class="n">O_CREAT</span> <span class="o">|</span> <span class="n">O_EXCL</span><span class="p">,</span> <span class="n">S_IRUSR</span> <span class="o">|</span> <span class="n">S_IWUSR</span><span class="p">,</span> <span class="mi">0</span><span class="p">);</span>
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|
|
|
<span class="cm">/* Create the pool of worker threads; each will */</span>
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|
<span class="n">pthread_t</span> <span class="n">threads</span><span class="p">[</span><span class="n">number_of_threads</span><span class="p">];</span>
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|
<span class="n">memset</span> <span class="p">(</span><span class="n">threads</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="k">sizeof</span> <span class="p">(</span><span class="n">threads</span><span class="p">));</span>
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|
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|
<span class="kt">size_t</span> <span class="n">i</span><span class="p">;</span>
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|
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">number_of_threads</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span>
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|
<span class="n">pthread_create</span> <span class="p">(</span><span class="o">&</span><span class="n">threads</span><span class="p">[</span><span class="n">i</span><span class="p">],</span> <span class="nb">NULL</span><span class="p">,</span> <span class="n">mod_power_consumer</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">);</span>
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<span class="cm">/* Producer side of the producer/consumer. Select a pair</span>
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|
<span class="cm"> of prime/power and add the entry to the queue. */</span>
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|
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">primes_length</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span>
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|
<span class="p">{</span>
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|
<span class="k">struct</span> <span class="n">queue_entry</span> <span class="n">entry</span><span class="p">;</span>
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<span class="n">entry</span><span class="p">.</span><span class="n">base</span> <span class="o">=</span> <span class="n">primes</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>
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|
<span class="n">entry</span><span class="p">.</span><span class="n">power</span> <span class="o">=</span> <span class="n">powers</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>
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|
|
<span class="cm">/* Wait until space is ready */</span>
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|
<span class="n">sem_wait</span> <span class="p">(</span><span class="n">space_available</span><span class="p">);</span>
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<span class="n">queue</span><span class="p">[</span><span class="n">next_in</span><span class="p">]</span> <span class="o">=</span> <span class="n">entry</span><span class="p">;</span>
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|
<span class="n">next_in</span> <span class="o">=</span> <span class="p">(</span><span class="n">next_in</span> <span class="o">+</span> <span class="mi">1</span><span class="p">)</span> <span class="o">%</span> <span class="n">QUEUE_SIZE</span><span class="p">;</span>
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|
|
|
<span class="cm">/* Signal that an item was added */</span>
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|
<span class="n">sem_post</span> <span class="p">(</span><span class="n">item_ready</span><span class="p">);</span>
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<span class="p">}</span>
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|
<span class="cm">/* No more powers needed from the array */</span>
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|
<span class="n">free</span> <span class="p">(</span><span class="n">powers</span><span class="p">);</span>
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<span class="n">powers</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span>
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|
<span class="cm">/* Now start filling the queue with -1 values to terminate</span>
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|
<span class="cm"> the helper threads */</span>
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|
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">number_of_threads</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span>
|
|
<span class="p">{</span>
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|
<span class="k">struct</span> <span class="n">queue_entry</span> <span class="n">blank</span><span class="p">;</span>
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|
<span class="n">blank</span><span class="p">.</span><span class="n">base</span> <span class="o">=</span> <span class="o">-</span><span class="mi">1</span><span class="p">;</span>
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<span class="n">blank</span><span class="p">.</span><span class="n">power</span> <span class="o">=</span> <span class="o">-</span><span class="mi">1</span><span class="p">;</span>
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|
|
|
<span class="cm">/* Wait for space */</span>
|
|
<span class="n">sem_wait</span> <span class="p">(</span><span class="n">space_available</span><span class="p">);</span>
|
|
<span class="n">queue</span><span class="p">[</span><span class="n">next_in</span><span class="p">]</span> <span class="o">=</span> <span class="n">blank</span><span class="p">;</span>
|
|
<span class="n">next_in</span> <span class="o">=</span> <span class="p">(</span><span class="n">next_in</span> <span class="o">+</span> <span class="mi">1</span><span class="p">)</span> <span class="o">%</span> <span class="n">QUEUE_SIZE</span><span class="p">;</span>
|
|
|
|
<span class="cm">/* Signal that an item was added */</span>
|
|
<span class="n">sem_post</span> <span class="p">(</span><span class="n">item_ready</span><span class="p">);</span>
|
|
<span class="p">}</span>
|
|
|
|
<span class="cm">/* Join all of the threads when finished */</span>
|
|
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">number_of_threads</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span>
|
|
<span class="n">pthread_join</span> <span class="p">(</span><span class="n">threads</span><span class="p">[</span><span class="n">i</span><span class="p">],</span> <span class="nb">NULL</span><span class="p">);</span>
|
|
|
|
<span class="cm">/* Clean up all synchronization primitives */</span>
|
|
<span class="n">pthread_mutex_destroy</span> <span class="p">(</span><span class="o">&</span><span class="n">mutex</span><span class="p">);</span>
|
|
<span class="n">sem_close</span> <span class="p">(</span><span class="n">item_ready</span><span class="p">);</span>
|
|
<span class="n">sem_close</span> <span class="p">(</span><span class="n">space_available</span><span class="p">);</span>
|
|
<span class="n">sem_unlink</span> <span class="p">(</span><span class="n">SEM_AVAILABLE</span><span class="p">);</span>
|
|
<span class="n">sem_unlink</span> <span class="p">(</span><span class="n">SEM_READY</span><span class="p">);</span>
|
|
|
|
<span class="n">printf</span> <span class="p">(</span><span class="s">"Product is %"</span> <span class="n">PRIu64</span> <span class="s">"</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span> <span class="n">result</span><span class="p">);</span>
|
|
|
|
<span class="k">return</span> <span class="n">EXIT_SUCCESS</span><span class="p">;</span>
|
|
<span class="p">}</span>
|
|
|
|
<span class="cm">/* Consumer thread. Each thread runs until it receives a</span>
|
|
<span class="cm"> power of -1 (indicating finished). After a base/power</span>
|
|
<span class="cm"> pair is pulled from the queue, the thread will compute</span>
|
|
<span class="cm"> base^power mod modulus, then multiple that by the global</span>
|
|
<span class="cm"> result product. */</span>
|
|
<span class="kt">void</span> <span class="o">*</span>
|
|
<span class="nf">mod_power_consumer</span> <span class="p">(</span><span class="kt">void</span> <span class="o">*</span> <span class="n">_args</span><span class="p">)</span>
|
|
<span class="p">{</span>
|
|
<span class="k">struct</span> <span class="n">queue_entry</span> <span class="n">entry</span><span class="p">;</span>
|
|
<span class="k">while</span> <span class="p">(</span><span class="nb">true</span><span class="p">)</span>
|
|
<span class="p">{</span>
|
|
<span class="cm">/* Consumer side waits until an item is ready */</span>
|
|
<span class="n">sem_wait</span> <span class="p">(</span><span class="n">item_ready</span><span class="p">);</span>
|
|
|
|
<span class="cm">/* Multiple consumers, so lock the queue */</span>
|
|
<span class="n">pthread_mutex_lock</span> <span class="p">(</span><span class="o">&</span><span class="n">mutex</span><span class="p">);</span>
|
|
<span class="n">entry</span> <span class="o">=</span> <span class="n">queue</span><span class="p">[</span><span class="n">next_out</span><span class="p">];</span>
|
|
<span class="n">next_out</span> <span class="o">+=</span> <span class="mi">1</span><span class="p">;</span>
|
|
<span class="n">next_out</span> <span class="o">%=</span> <span class="n">QUEUE_SIZE</span><span class="p">;</span>
|
|
<span class="n">pthread_mutex_unlock</span> <span class="p">(</span><span class="o">&</span><span class="n">mutex</span><span class="p">);</span>
|
|
|
|
<span class="cm">/* Let producer no there's at least one space */</span>
|
|
<span class="n">sem_post</span> <span class="p">(</span><span class="n">space_available</span><span class="p">);</span>
|
|
|
|
<span class="cm">/* Check for termination signal */</span>
|
|
<span class="k">if</span> <span class="p">(</span><span class="n">entry</span><span class="p">.</span><span class="n">power</span> <span class="o">==</span> <span class="o">-</span><span class="mi">1</span><span class="p">)</span> <span class="k">break</span><span class="p">;</span>
|
|
|
|
<span class="cm">/* Computer base^power, then multiple result with</span>
|
|
<span class="cm"> the global product */</span>
|
|
<span class="kt">uint64_t</span> <span class="n">modp</span> <span class="o">=</span> <span class="n">mod_power</span> <span class="p">(</span><span class="n">entry</span><span class="p">.</span><span class="n">base</span><span class="p">,</span> <span class="n">entry</span><span class="p">.</span><span class="n">power</span><span class="p">);</span>
|
|
<span class="n">pthread_mutex_lock</span> <span class="p">(</span><span class="o">&</span><span class="n">mutex</span><span class="p">);</span>
|
|
<span class="k">if</span> <span class="p">(</span><span class="n">entry</span><span class="p">.</span><span class="n">power</span> <span class="o">></span> <span class="mi">1</span><span class="p">)</span>
|
|
<span class="n">printf</span> <span class="p">(</span><span class="s">"%"</span> <span class="n">PRIu64</span> <span class="s">" ^ %"</span> <span class="n">PRIu64</span> <span class="s">" mod %"</span> <span class="n">PRIu64</span> <span class="s">" = %"</span> <span class="n">PRIu64</span> <span class="s">"</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span>
|
|
<span class="n">entry</span><span class="p">.</span><span class="n">base</span><span class="p">,</span> <span class="n">entry</span><span class="p">.</span><span class="n">power</span><span class="p">,</span> <span class="n">modulus</span><span class="p">,</span> <span class="n">modp</span><span class="p">);</span>
|
|
<span class="n">result</span> <span class="o">*=</span> <span class="n">modp</span><span class="p">;</span>
|
|
<span class="n">result</span> <span class="o">%=</span> <span class="n">modulus</span><span class="p">;</span>
|
|
<span class="n">pthread_mutex_unlock</span> <span class="p">(</span><span class="o">&</span><span class="n">mutex</span><span class="p">);</span>
|
|
<span class="p">}</span>
|
|
|
|
<span class="n">pthread_exit</span> <span class="p">(</span><span class="nb">NULL</span><span class="p">);</span>
|
|
<span class="p">}</span>
|
|
|
|
<span class="cm">/* Intentionally slow mod power routine. Computes</span>
|
|
<span class="cm"> base^power mod modulus by multiplying a running</span>
|
|
<span class="cm"> product repeatedly by the base. Slow enough to</span>
|
|
<span class="cm"> see a speedup from parallel executions. */</span>
|
|
<span class="kt">uint64_t</span>
|
|
<span class="nf">mod_power</span> <span class="p">(</span><span class="kt">uint64_t</span> <span class="n">base</span><span class="p">,</span> <span class="kt">uint64_t</span> <span class="n">power</span><span class="p">)</span>
|
|
<span class="p">{</span>
|
|
<span class="kt">uint64_t</span> <span class="n">index</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
|
|
<span class="kt">uint64_t</span> <span class="n">product</span> <span class="o">=</span> <span class="mi">1</span><span class="p">;</span>
|
|
|
|
<span class="k">while</span> <span class="p">(</span><span class="n">index</span> <span class="o"><</span> <span class="n">power</span><span class="p">)</span>
|
|
<span class="p">{</span>
|
|
<span class="n">product</span> <span class="o">*=</span> <span class="n">base</span><span class="p">;</span>
|
|
<span class="n">product</span> <span class="o">%=</span> <span class="n">modulus</span><span class="p">;</span>
|
|
<span class="n">index</span><span class="o">++</span><span class="p">;</span>
|
|
<span class="p">}</span>
|
|
<span class="k">return</span> <span class="n">product</span><span class="p">;</span>
|
|
<span class="p">}</span>
|
|
|
|
<span class="cm">/* Create an array of random powers for the primes.</span>
|
|
<span class="cm"> The threshold parameter determines (approximately)</span>
|
|
<span class="cm"> what percentage of these powers are non-zero. */</span>
|
|
<span class="kt">uint64_t</span> <span class="o">*</span>
|
|
<span class="nf">randomize_powers</span> <span class="p">(</span><span class="kt">size_t</span> <span class="n">length</span><span class="p">,</span> <span class="kt">unsigned</span> <span class="n">seed</span><span class="p">,</span>
|
|
<span class="kt">double</span> <span class="n">threshold</span><span class="p">,</span> <span class="kt">size_t</span> <span class="n">minimum</span><span class="p">)</span>
|
|
<span class="p">{</span>
|
|
<span class="kt">size_t</span> <span class="n">i</span><span class="p">;</span>
|
|
<span class="kt">uint64_t</span> <span class="o">*</span><span class="n">pows</span> <span class="o">=</span> <span class="n">calloc</span> <span class="p">(</span><span class="n">length</span><span class="p">,</span> <span class="k">sizeof</span> <span class="p">(</span><span class="kt">uint64_t</span><span class="p">));</span>
|
|
<span class="n">srand</span> <span class="p">(</span><span class="n">seed</span><span class="p">);</span>
|
|
<span class="kt">size_t</span> <span class="n">randoms</span> <span class="o">=</span> <span class="n">length</span> <span class="o">*</span> <span class="n">threshold</span><span class="p">;</span>
|
|
|
|
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">randoms</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span>
|
|
<span class="p">{</span>
|
|
<span class="kt">size_t</span> <span class="n">index</span> <span class="o">=</span> <span class="n">rand</span> <span class="p">()</span> <span class="o">%</span> <span class="n">length</span><span class="p">;</span>
|
|
<span class="n">pows</span><span class="p">[</span><span class="n">index</span><span class="p">]</span> <span class="o">=</span> <span class="p">(</span><span class="n">rand</span> <span class="p">()</span> <span class="o">%</span> <span class="mi">10</span><span class="p">)</span> <span class="o">*</span> <span class="n">minimum</span><span class="p">;</span>
|
|
<span class="n">pows</span><span class="p">[</span><span class="n">index</span><span class="p">]</span> <span class="o">+=</span> <span class="n">rand</span> <span class="p">()</span> <span class="o">%</span> <span class="n">minimum</span><span class="p">;</span>
|
|
<span class="p">}</span>
|
|
<span class="k">return</span> <span class="n">pows</span><span class="p">;</span>
|
|
<span class="p">}</span>
|
|
</pre></div>
|
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</td></tr></table></div>
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«  <a id="prevmod1" href="CigSmokers.html">8.6. Cigarette Smokers Problem and the Limits of Semaphores and Locks</a>
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