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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - inplace_merge should not apply more than (last - first) - 1 comparisons if enough additional memory is available"
href="http://llvm.org/bugs/show_bug.cgi?id=22427">22427</a>
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<th>Summary</th>
<td>inplace_merge should not apply more than (last - first) - 1 comparisons if enough additional memory is available
</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>All
</td>
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<th>OS</th>
<td>All
</td>
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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
</td>
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>kariya_mitsuru@hotmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu, mclow.lists@gmail.com
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</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=13787" name="attach_13787" title="clang++ -v">attachment 13787</a> <a href="attachment.cgi?id=13787&action=edit" title="clang++ -v">[details]</a></span>
clang++ -v
Please see the sample code below.
================================= sample code =================================
#include <algorithm>
#include <iostream>
#include <vector>
int main()
{
std::vector<int> v = { 1, 3, 5, 2, 4, 6 };
int count = 0;
std::inplace_merge(v.begin(), v.end() - 3, v.end(),
[&count](int lhs, int rhs) -> bool { ++count; return lhs < rhs; });
std::for_each(v.begin(), v.end(), [](int x) { std::cout << x << ", "; });
std::cout << std::endl << count << " comparisons" << std::endl;
}
================================= sample code =================================
================================= output =================================
1, 2, 3, 4, 5, 6,
8 comparisons
================================= output =================================
cf. <a href="http://melpon.org/wandbox/permlink/u0NiYiwQ1fNUk7je">http://melpon.org/wandbox/permlink/u0NiYiwQ1fNUk7je</a>
The C++11 standard 25.4.4[alg.merge]/p.8 says, "When enough additional memory
is available, (last - first) - 1 comparisons."
I believe that enough additional memory is available in the sample code above,
so it should apply at most 5 comparisons.</pre>
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