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  <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
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  PRISM Manual | ThePRISMLanguage / MultipleInitialStates 
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      <p><a class='wikilink' href='Main.html'>The PRISM Language</a> /
  </p><h1>Multiple Initial States</h1>
  
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  <div id='wikitext'>
  <p>Typically, a <a class='wikilink' href='ModulesAndVariables.html'>variable</a> declaration
  specifies the initial value for that variable.
  The <em>initial state</em> for the model is then defined by the initial value for all variables.
  It is possible, however, to specify that a model has <em>multiple</em> initial states.
  This is done using the <code><strong>init</strong>...<strong>endinit</strong></code> construct,
  which can be placed anywhere in the file except within a module definition,
  and removing any initial values from variable declarations.
  Between the <code><strong>init</strong></code> and <code><strong>endinit</strong></code> keywords, there should be a
  predicate over all the variables of the model.
  Any state which satisfies this predicate is an initial state.
  </p>
  <p class='vspace'>Consider again <a class='wikilink' href='Example1.html'>Example 1</a>.
  As it stands, there is a single initial state <code>(0,0)</code> (i.e.  <code>x=0</code> and <code>y=0</code>).
  If we remove the <code><strong>init</strong> 0</code> part of both variable declarations
  and add the following to the end of the file:
  </p>
  <div class='vspace'></div>
  <div class='sourceblock ' id='sourceblock1'>
    <div class='sourceblocktext'><div class="prism"><span class="prismkeyword">init</span> <span class="prismident">x</span>=<span class="prismnum">0</span> <span class="prismkeyword">endinit</span><br/>
  </div></div>
    <div class='sourceblocklink'><a href='http://prismmodelchecker.localhost/manual/ThePRISMLanguage/MultipleInitialStates?action=sourceblock&amp;num=1' type='text/plain'>[&#036;[Get Code]]</a></div>
  </div>
  
  <p class='vspace'>there will be three initial states: <code>(0,0)</code>, <code>(0,1)</code> and <code>(0,2)</code>.
  Similarly, we could instead add:
  </p>
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  <div class='sourceblock ' id='sourceblock2'>
    <div class='sourceblocktext'><div class="prism"><span class="prismkeyword">init</span> <span class="prismident">x</span>+<span class="prismident">y</span>=<span class="prismnum">1</span> <span class="prismkeyword">endinit</span><br/>
  </div></div>
    <div class='sourceblocklink'><a href='http://prismmodelchecker.localhost/manual/ThePRISMLanguage/MultipleInitialStates?action=sourceblock&amp;num=2' type='text/plain'>[&#036;[Get Code]]</a></div>
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  <p class='vspace'>in which case there would be two initial states: <code>(0,1)</code> and <code>(1,0)</code>.
  </p>
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