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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Set existence with numeric values slower than numeric object property existence"
href="https://bugs.webkit.org/show_bug.cgi?id=151233">151233</a>
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<th>Summary</th>
<td>Set existence with numeric values slower than numeric object property existence
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<th>Classification</th>
<td>Unclassified
</td>
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<th>Product</th>
<td>WebKit
</td>
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<th>Version</th>
<td>WebKit Nightly Build
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<th>Hardware</th>
<td>Unspecified
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<th>OS</th>
<td>Unspecified
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>Normal
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<th>Priority</th>
<td>P2
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<th>Component</th>
<td>JavaScriptCore
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>joepeck@webkit.org
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<th>CC</th>
<td>keith_miller@apple.com, sbarati@apple.com, utatane.tea@gmail.com
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<pre>Created <span class=""><a href="attachment.cgi?id=265448" name="attach_265448" title="[TEST] Set Existence Benchmark">attachment 265448</a> <a href="attachment.cgi?id=265448&action=edit" title="[TEST] Set Existence Benchmark">[details]</a></span>
[TEST] Set Existence Benchmark
* SUMMARY
Set existence with numeric values slower than numeric object property existence.
In Web Inspector we were converting a bunch of uses of "Object as Set" and "Object as Map" to Set/Map objects. I wrote a small benchmark to compare possible performance differences. Existence checks for large dense Sets with primitives is worse than existence checks in large dense Objects.
object[number] - 17ms
number in object - 84ms
set.has(number) - 622ms
For numeric keys object was significantly faster than Set.
For other key types the effect was not as large.
See attached test case.
* NOTES
- Not sure how realistic the test is for real world code. Especially given Set's major advantage is non-primitive keys.</pre>
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