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<p class="MsoNormal"><span style="font-family:"Courier New"">Hi Michaël,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Thanks for you feedback.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">> it's currently possible to know for a given type which VectorSpecies is preferred<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">> on the current platform.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">I think the preferred species is usually the largest available species.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">> an application developer would want to know which Operator will be preferred (i.e.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">> backed by an appropriate SIMD instruction) on a targeted platform. Similarly, a<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">> library developer would want to be able to pick at runtime between different<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">> implementations of an algorithm.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Usually, the larger species would have better performance since more data could be<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">handled in just one time. That’s true that it’s architecture dependent. Even though<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">some instructions have low throughput in a larger size, a well implemented backend<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">should choose the optimal instructions and should not trouble the Java developers.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">Have you ever found a case that has better performance but with a smaller species on<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">any platform? If there is, perhaps some micro-architecture optimizations should be done.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New"">- Eric<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Courier New""><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>From:</b> panama-dev <panama-dev-retn@openjdk.org> <b>On Behalf Of
</b>Michaël Figuière<br>
<b>Sent:</b> Saturday, October 15, 2022 1:56 AM<br>
<b>To:</b> panama-dev@openjdk.org<br>
<b>Subject:</b> [Vector API] Missing a way to know which operators are preferred<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hello,<br>
<br>
A suggestion based on my small experience with the Vector API: it's currently possible to know for<o:p></o:p></p>
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<p class="MsoNormal">a given type which VectorSpecies is preferred on the current platform, but it's not the case for<o:p></o:p></p>
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<p class="MsoNormal">Operator. As the Vector API is all about improved performance, an application developer would<o:p></o:p></p>
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<p class="MsoNormal">want to know which Operator will be preferred (i.e. backed by an appropriate SIMD instruction) on<o:p></o:p></p>
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<p class="MsoNormal">a targeted platform. Similarly, a library developer would want to be able to pick at runtime between<o:p></o:p></p>
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<p class="MsoNormal">different implementations of an algorithm.<o:p></o:p></p>
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<p class="MsoNormal"><br>
That could look like:<br>
<br>
boolean VectorOperators.Operator#isPreferredWith(VectorSpecies)<br>
<br>
I haven't looked at the implementation details but I assume that it would be doable as the Operator<o:p></o:p></p>
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<p class="MsoNormal">actual implementation is already picked based on CPU instructions availability.<br>
<br>
Thanks,<br>
Michaël<o:p></o:p></p>
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