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    copied!<p>I think that you can use <code>thrust::unique</code> with a predicate as it's shown in <a href="https://stackoverflow.com/questions/5521091/thrust-removing-duplicates-in-key-value-arrays">Thrust: Removing duplicates in key-value arrays</a>. Actually, we can do it because of the following characteristic of <code>unique</code>:</p> <blockquote> <p>For each group of consecutive elements in the range [first, last) with the same value, <code>unique</code> removes <strong>all but the first</strong> element of the group.</p> </blockquote> <p>So, you should define a predicate to test for <em>pseudo</em>-equality that will return <code>true</code> for tuples that have the same key and all values are smaller in the first tuple:</p> <pre><code> typedef thrust::tuple&lt;int, int, int, int&gt; tuple_t; // a functor which defines your *uniqueness* condition struct tupleEqual { __host__ __device__ bool operator()(tuple_t x, tuple_t y) { return ( (x.get&lt;0&gt;() == y.get&lt;0&gt;()) // same key &amp;&amp; (x.get&lt;1&gt;() &lt;= y.get&lt;1&gt;()) // all values are smaller &amp;&amp; (x.get&lt;2&gt;() &lt;= y.get&lt;2&gt;()) &amp;&amp; (x.get&lt;3&gt;() &lt;= y.get&lt;3&gt;())); } }; </code></pre> <p>And you have to apply it to a <strong>sorted</strong> collection. In this way, only the first tuple (the smallest) will not be removed. A tuple with the same key and a bigger value in V1, V2 or V3 will yield <code>false</code> so it won't be removed.</p> <pre><code> typedef thrust::device_vector&lt; int &gt; IntVector; typedef IntVector::iterator IntIterator; typedef thrust::tuple&lt; IntIterator, IntIterator, IntIterator, IntIterator &gt; IntIteratorTuple; typedef thrust::zip_iterator&lt; IntIteratorTuple &gt; ZipIterator; IntVector keyVector; IntVector valVector1, valVector2, valVector3; tupleEqual predicate; ZipIterator newEnd = thrust::unique( thrust::make_zip_iterator( thrust::make_tuple( keyVector.begin(), valVector1.begin(), valVector2.begin(), valVector3.begin() ) ), thrust::make_zip_iterator( thrust::make_tuple( keyVector.end(), valVector1.end(), valVector2.end(), valVector3.end() ) ), predicate ); IntIteratorTuple endTuple = newEnd.get_iterator_tuple(); keyVector.erase( thrust::get&lt;0&gt;( endTuple ), keyVector.end() ); valVector1.erase( thrust::get&lt;1&gt;( endTuple ), valVector1.end() ); valVector2.erase( thrust::get&lt;2&gt;( endTuple ), valVector2.end() ); valVector3.erase( thrust::get&lt;3&gt;( endTuple ), valVector3.end() ); </code></pre>
 

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