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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - duration_cast has rounding bug converting long double seconds to long long nanoseconds"
href="http://llvm.org/bugs/show_bug.cgi?id=20537">20537</a>
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<th>Summary</th>
<td>duration_cast has rounding bug converting long double seconds to long long nanoseconds
</td>
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<th>Product</th>
<td>libc++
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>vlovich@gmail.com
</td>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu, mclow.lists@gmail.com
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=12856" name="attach_12856" title="Sample code demonstrating rounding bug">attachment 12856</a> <a href="attachment.cgi?id=12856&action=edit" title="Sample code demonstrating rounding bug">[details]</a></span>
Sample code demonstrating rounding bug
Converting from floating-point seconds to nanoseconds, there is a demonstrable
rounding bug. It looks like converting from floating-point seconds to integral
nanoseconds uses division by 1e-9 instead of multiplication by 1e9 which causes
rounding error when the floating-point storage is long double.
Sample code attached.
This problem does not appear to occur in gcc/libstdc++.</pre>
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