rmuir commented on code in PR #12731:
URL: https://github.com/apache/lucene/pull/12731#discussion_r1375248973
##########
lucene/core/src/java20/org/apache/lucene/internal/vectorization/PanamaVectorUtilSupport.java:
##########
@@ -77,6 +77,47 @@ final class PanamaVectorUtilSupport implements
VectorUtilSupport {
VectorizationProvider.TESTS_FORCE_INTEGER_VECTORS ||
(isAMD64withoutAVX2 == false);
}
+ private static final String MANAGEMENT_FACTORY_CLASS =
"java.lang.management.ManagementFactory";
+ private static final String HOTSPOT_BEAN_CLASS =
"com.sun.management.HotSpotDiagnosticMXBean";
+
+ // best effort to see if FMA is fast (this is architecture-independent
option)
+ private static boolean hasFastFMA() {
+ // on ARM cpus, FMA works fine but is a slight slowdown: don't use it.
+ if (Constants.OS_ARCH.equals("amd64") == false) {
+ return false;
+ }
+ try {
+ final Class<?> beanClazz = Class.forName(HOTSPOT_BEAN_CLASS);
+ // we use reflection for this, because the management factory is not part
+ // of Java 8's compact profile:
+ final Object hotSpotBean =
Review Comment:
surely we can leave comments about the module system to another issue. It
was somehow ok for ramusageestimator to do this, but not ok for vectors code?
Honestly, i havent a clue about the module system (nor a care) and no idea
how it works or what 'requires static' means or any of that. To me, it looks
like more overengineered java garbage (sorry). So I'm ill-equipped to be
updating comments inside RAMUsageEstimator. I just want to try to improve the
vectorization here.
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