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<p>Hi,</p>
<p>I'm curious about the restriction when loading from heap backed
memory segments. E.g.<br>
</p>
<div style="background-color:#1e1f22;color:#bcbec4">
<pre
style="font-family:'JetBrains Mono',monospace;font-size:9.8pt;"> <span
style="color:#5f826b;font-style:italic;"> * </span><span
style="color:#67a37c;font-style:italic;">@throws </span><span
style="color:#5f826b;font-style:italic;">IllegalArgumentException if the memory segment is a heap segment that is
</span><span style="color:#5f826b;font-style:italic;"> * not backed by a {</span><span
style="color:#67a37c;font-style:italic;">@code </span><span
style="color:#5f826b;font-style:italic;">byte[]} array.
</span><span style="color:#5f826b;font-style:italic;"> * </span><span
style="color:#67a37c;font-style:italic;">...</span><span
style="color:#cf8e6d;">
</span> FloatVector <span style="color:#56a8f5;">fromMemorySegment</span>(VectorSpecies<Float> species, MemorgSegment ms, ...)</pre>
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<p></p>
<p>Which results in:<br>
</p>
<p>jshell> float[] arr = new float[] { 1, 2, 3, 4, 5, 6, 7, 8 }<br>
arr ==> float[8] { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 }<br>
<br>
jshell> var vec =
FloatVector.fromMemorySegment(FloatVector.SPECIES_PREFERRED,
MemorySegment.ofArray(arr), 0, ByteOrder.nativeOrder())<br>
| Exception java.lang.IllegalArgumentException<br>
| at ScopedMemoryAccess.loadFromMemorySegment
(ScopedMemoryAccess.java:334)<br>
| at FloatVector.fromMemorySegment0Template
(FloatVector.java:3353)<br>
| at Float128Vector.fromMemorySegment0
(Float128Vector.java:864)<br>
| at FloatVector.fromMemorySegment (FloatVector.java:2986)<br>
| at do_it$Aux (#43:1)<br>
| at (#43:1)<br>
<br>
</p>
<p>I can see that this is deliberate ...</p>
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<pre
style="font-family:'JetBrains Mono',monospace;font-size:9.8pt;"><span
style="color:#16baac;"> V </span><span style="color:#56a8f5;">loadFromMemorySegmentMasked</span>(...) {
<span style="color:#7a7e85;">// @@@ Smarter alignment checking if accessing heap segment backing non-byte[] array
</span><span style="color:#7a7e85;"> </span><span
style="color:#cf8e6d;">if </span>(msp.maxAlignMask() > <span
style="color:#2aacb8;">1</span>) {
<span style="color:#cf8e6d;">throw new </span>IllegalArgumentException();
}</pre>
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<p>Is this just temporary? I would expect the alignment to be as if
`<font face="monospace">ValueLayout.JAVA_FLOAT.withByteAlignment(1)</font>`,
no? Is the intent to eventually support other non-byte primitive
array typed, and to require and check alignment? It should just
work, right?</p>
<p>--<br>
</p>
<p>The reason I ask about this is that over in Luceneland we're
considering a switch to loading vector data from float[] to
MemorySegment - which allows to load search vectors directly from
the mmapped index file. But we still have some code paths which
have float[], which may or may not be coming from the mmapped
file. So we end up with something like this:</p>
<p><font face="monospace"> dotProduct(float[] a, float[] b)</font></p>
<p><font face="monospace"> dotProduct(float[] a, MemorySegment b)</font></p>
<p><font face="monospace"> dotProduct(</font><font face="monospace">MemorySegment</font><font
face="monospace"> a, MemorySegment b)</font></p>
<p></p>
<p></p>
<p></p>
<p>... and we have cosine and Euclidean distance too. We can of
course write the three variants of the code (and we've done this),
just that it would be desirable to have the float[] accepting
methods just wrap and delegate to the MemorySegment variant. In
our use case, we don't slice or offset into the heap segment, but
I do see how things could get misaligned quite quickly, but again
I expect this to behave as if with byte alignment(1).<br>
</p>
<p>Thanks,</p>
<p>-Chris.<br>
</p>
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