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    <p>For any optimization, it's always best to test, test, test. I would try at least sorting networks and insertion sort. If I were betting, I'd put my money on insertion sort based on past experience.</p> <p>Do you know anything about the input data? Some algorithms will perform better with certain kinds of data. For example, insertion sort performs better on sorted or almost-sorted dat, so it will be the better choice if there's an above-average chance of almost-sorted data.</p> <p>The algorithm you posted is similar to an insertion sort, but it looks like you've minimized the number of swaps at the cost of more comparisons. Comparisons are far more expensive than swaps, though, because branches can cause the instruction pipeline to stall.</p> <p>Here's an insertion sort implementation:</p> <pre><code>static __inline__ int sort6(int *d){ int i, j; for (i = 1; i &lt; 6; i++) { int tmp = d[i]; for (j = i; j &gt;= 1 &amp;&amp; tmp &lt; d[j-1]; j--) d[j] = d[j-1]; d[j] = tmp; } } </code></pre> <p>Here's how I'd build a sorting network. First, use <a href="http://pages.ripco.net/~jgamble/nw.html" rel="noreferrer">this site</a> to generate a minimal set of SWAP macros for a network of the appropriate length. Wrapping that up in a function gives me:</p> <pre><code>static __inline__ int sort6(int * d){ #define SWAP(x,y) if (d[y] &lt; d[x]) { int tmp = d[x]; d[x] = d[y]; d[y] = tmp; } SWAP(1, 2); SWAP(0, 2); SWAP(0, 1); SWAP(4, 5); SWAP(3, 5); SWAP(3, 4); SWAP(0, 3); SWAP(1, 4); SWAP(2, 5); SWAP(2, 4); SWAP(1, 3); SWAP(2, 3); #undef SWAP } </code></pre>
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    1. POFastest sort of fixed length 6 int array
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    1. USMartijn
    1. USDaniel Stutzbach
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    1. CO+1: nice, you did it with 12 exchanges rather than the 13 in my hand-coded and empirically derived network above. I'd give you another +1 if I could for the link to the site that generates networks for you - now bookmarked.
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      1. USPaul R
    2. COThis is a fantastic idea for a general purpose sorting function if you expect the majority of requests to be small sized arrays. Use a switch statement for the cases that you want to optimize, using this procedure; let the default case use a library sort function.
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      1. USMark Ransom
    3. CO@kriss Thanks. I fixed the macro.
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