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<concept id="GUID-C7B748CF-D080-5448-98AF-1634D821E713" xml:lang="en"><title> SMP
Example</title><shortdesc>This example demonstrates symmetric multiprocessing using multiple
threads. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>This example shows the differences between code running in a unicore environment
and in a multiprocessor environment.</p>
<section id="GUID-7AC2BE12-4F01-4140-8379-672475DE7681"><title>Download</title> <p>Click on the following link to download
the example: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/zips/guid-577596d8-76a2-4a41-aa0f-deefe5638e23.zip" scope="external">SmpExample.zip</xref></p><p>Click: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/guid-577596d8-76a2-4a41-aa0f-deefe5638e23.html" scope="peer">browse</xref> to view the example code. </p> </section>
<section id="GUID-7A70847E-40A2-4267-9BD4-36F88F48C84A"><title>Class summary</title><ul>
<li><p><xref href="GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5.dita"><apiname>RThread</apiname></xref> - A handle to a thread.</p></li>
<li><p><xref href="GUID-F4A68645-2265-307F-B951-8295827E000B.dita"><apiname>RDbStoreDatabase</apiname></xref> - DBMS Store database implementation</p></li>
</ul></section>
<section id="GUID-BE13F08D-09FD-41DF-9210-D46EBECADA69"><title>Design and implementation</title> <p>The example creates two
databases named DBforSMP1.db and DBforSMP2.db and three threads: </p> <ul>
<li id="GUID-F4EE1C84-FE30-5C99-872B-1881D852CAEA"><p> <codeph>WriterThread1</codeph>:
It creates the DBforSMP1.db database and writes integers to it. The thread
has the lowest priority amongst all the threads. </p> </li>
<li id="GUID-7B2D0419-E069-59FA-A6CE-70EBC203F656"><p> <codeph>WriterThread2</codeph>:
It creates the DBforSMP2.db database and writes some integers to it. The thread
has highest priority amongst all the threads. </p> </li>
<li id="GUID-7C9584F2-E6C8-5A02-B4C2-4845CF4BAA36"><p> <codeph>ReaderThread</codeph>:
It reads the two databases and prints the output to the console. It has normal
priority. </p> </li>
</ul> <p>In a unicore enviroment, the threads are executed according to their
priorities. This means first <codeph> WriterThread2</codeph>, then <codeph>ReaderThread</codeph> and
finally <codeph>WriterThread1</codeph> is executed. Hence <codeph>ReaderThead</codeph> can
only print the contents of the DBforSMP2.db in the console because DBforSMP1
is empty. in an SMP environment, threads run simultaneously and <codeph>ReaderThread</codeph> can
print the contents of both the databases. </p> </section>
<section id="GUID-3686F166-C4DD-4269-9B9C-F0027F53547E"><title>Building and configuring</title> <p>To build the example: </p> <ul>
<li id="GUID-037442C7-2436-5152-9A3E-9DC0B4283A9C-GENID-1-6-1-13-1-1-4-1-4-1-25-1-30-1-3-5-3-1"><p>The example builds an
executable called <filepath>smpexample.exe</filepath> in the standard location. </p> </li>
<li id="GUID-B7C849B9-0885-5253-A78B-71854F86D772-GENID-1-6-1-13-1-1-4-1-4-1-25-1-30-1-3-5-3-2"><p>You can build the example
from your IDE or the command line. </p> <p>If you use an IDE, import the <filepath>bld.inf</filepath> file
of the example into your IDE, and use the build command of the IDE. </p> <p>If
you use the command line, open a command prompt, and set the current directory
to the source code directory of the example. You can then build the example
with the SBSv1 build tools with the following commands: </p> <p><userinput>bldmake
bldfiles</userinput> </p> <p><userinput>abld build</userinput> </p> <p><xref href="GUID-793A5EF9-CC16-5EEB-9011-6431EA76EB15.dita">How to use bldmake</xref> and <xref href="GUID-B6B54E07-3B34-5D5C-8815-93383FA8FB4B.dita">How to use abld</xref> describe
how to use the SBSv1 build tools. </p> </li>
</ul> </section>
<section id="GUID-F773B722-7612-4BAF-99CB-84E39CE10C40"><title>Running the example</title> <p>To test the example in an SMP
environment, add <codeph>crazyscheduling on</codeph>in the <filepath>epoc32\data\epoc.ini</filepath> file.
This emulates SMP behaviour in the techview emulator. Execute the example
in both unicore and multiprocessor environment and see the difference. Run
the example following the instructions provided in the console. </p> </section>
</conbody></concept>