8319423: Improve Year.isLeap by checking divisibility by 16

Reviewed-by: naoto, rriggs

test/micro/org/openjdk/bench/java/time/LeapYearBench.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package org.openjdk.bench.java.time;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+import java.time.Duration;
+import java.time.Instant;
+import java.time.Year;
+import java.time.ZonedDateTime;
+import java.time.chrono.IsoChronology;
+import java.time.temporal.ChronoUnit;
+import java.util.GregorianCalendar;
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+/**
+ * Examine Year.leapYear-related operations
+ */
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.MICROSECONDS)
+@Warmup(iterations = 5, time = 1)
+@Measurement(iterations = 5, time = 1)
+@Fork(3)
+@State(Scope.Thread)
+public class LeapYearBench {
+
+    private long[] years;
+
+    private GregorianCalendar calendar;
+
+    @Setup
+    public void createInstants() {
+        // Large enough number of years to guarantee that the distribution of
+        // leap years is reasonably realistic
+        years = new long[2048];
+        final Random random = new Random(0);
+        for (int i = 0; i < years.length; i++) {
+            years[i] = random.nextLong(2000) + 2000;
+        }
+        calendar = GregorianCalendar.from(ZonedDateTime.now());
+    }
+
+    @Benchmark
+    public void isLeapYear(Blackhole bh) {
+        for (long year : years) {
+            bh.consume(Year.isLeap(year));
+        }
+    }
+
+    @Benchmark
+    public void isLeapYearChrono(Blackhole bh) {
+        for (long year : years) {
+            bh.consume(IsoChronology.INSTANCE.isLeapYear(year));
+        }
+    }
+
+    @Benchmark
+    public void isLeapYearGregorian(Blackhole bh) {
+        for (long year : years) {
+            bh.consume(calendar.isLeapYear((int)year));
+        }
+    }
+
+    public static boolean isLeapNeriSchneider(long year) {
+        int d = year % 100 != 0 ? 4 : 16;
+        return (year & (d - 1)) == 0;
+    }
+
+    @Benchmark
+    public void isLeapYearNS(Blackhole bh) {
+        for (long year : years) {
+            bh.consume(isLeapNeriSchneider(year));
+        }
+    }
+}