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Issue #6439 has been updated by Christopher Brooks.
<ul>
<li><strong>Status</strong> changed from <i>New</i> to <i>Closed</i></li>
<li><strong>Assignee</strong> changed from <i>Derik Barseghian</i> to <i>Christopher Brooks</i></li>
<li><strong>% Done</strong> changed from <i>0</i> to <i>100</i></li>
</ul>
<p>It is almost never a good idea to compare doubles without using an epsilon factor. Because of rounding, doubles are unlikely to precisely represent a value.</p>
<p>One workaround in the expression language is to use</p>
<p>close(value1, value2)</p>
<p>which is defined as:</p>
<p>Return true if the first argument<br />is close to the second (within<br />EPSILON, where EPSILON is<br />a static public variable of this<br />class)</p>
<p>Tokens also have an isCloseTo() method:</p>
<p>/** Test whether the value of this Token is close to the argument
* Token. The argument and this token are converted to
* equivalent types, and then compared. Generally, this is the
* higher of the type of this token and the argument type.
* Subclasses should implement the protected _isCloseTo() method
* to perform the correct type-specific operation.
* @see #isEqualTo
* @param rightArgument The token to test closeness of this token with.
* @param epsilon The value that we use to determine whether two
* tokens are close.
* @return A boolean token that contains the value true if the
* units of this token and the argument token are the same, and their
* values are close.
* @exception IllegalActionException If the argument token is not
* of a type that can be compared with this token, or the units
* are not the same. <br /> */<br /> public final BooleanToken isCloseTo(Token rightArgument, double epsilon)</p>
<p>See 13.4.1 Invoking Methods in <a class="external" href="http://ptolemy.eecs.berkeley.edu/books/Systems/chapters/Expressions.pdf">http://ptolemy.eecs.berkeley.edu/books/Systems/chapters/Expressions.pdf</a></p>
<hr />
<h1><a href="https://projects.ecoinformatics.org/ecoinfo/issues/6439#change-21517">Bug #6439: Double rounding fails in some cases while evaluating Expressions</a></h1>
<ul>
<li>Author: Owsiak Michal</li>
<li>Status: Closed</li>
<li>Priority: Urgent</li>
<li>Assignee: Christopher Brooks</li>
<li>Category: actors</li>
<li>Target version: 2.3.0</li>
<li>Bugzilla-Id: </li>
</ul>
<p>It seems that addition of doubles can produce values slightly different than they should to be.</p>
<p>Please take a look at attached workflow (simple_error.xml).</p>
<p>Condition that should be satisfied to escape the loop is: 1.7 > 1.5 + 0.1</p>
<p>However, loop is interrupted sooner, because of incorrect calculation of doubles. Value of "p" is set to: 1.6000000000000003</p>
<p>This, of course, makes it impossible to use doubles as check points for the loops.</p>
<p>However, it seems that casting to string and back works fine (take a look at second workflow - simple.xml)</p>
<p>Cheers</p>
<p>Michal</p>
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