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cow: CopyOnWriteArrayList - deterministic iterator-snapshot and synchronizedList CME demos, JMH read/write throughput, and the addLast/removeFirst fix for a real concurrent-writer race

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Claude
2026-10-01 12:09:44 +00:00
parent 2eaa464bad
commit 434054f246
17 changed files with 709 additions and 0 deletions
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cow/output/06-write-throughput-race.txt
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# Warmup Iteration 1: <failure>
java.lang.ArrayIndexOutOfBoundsException: Index 12 out of bounds for length 12
at java.base/java.util.concurrent.CopyOnWriteArrayList.elementAt(CopyOnWriteArrayList.java:397)
at java.base/java.util.concurrent.CopyOnWriteArrayList.remove(CopyOnWriteArrayList.java:538)
at com.ankurm.cow.WriteThroughputBenchmark.addRemove_fourConcurrentWriters(WriteThroughputBenchmark.java:68)
at com.ankurm.cow.jmh_generated.WriteThroughputBenchmark_addRemove_fourConcurrentWriters_jmhTest.addRemove_fourConcurrentWriters_thrpt_jmhStub(WriteThroughputBenchmark_addRemove_fourConcurrentWriters_jmhTest.java:147)
at com.ankurm.cow.jmh_generated.WriteThroughputBenchmark_addRemove_fourConcurrentWriters_jmhTest.addRemove_fourConcurrentWriters_Throughput(WriteThroughputBenchmark_addRemove_fourConcurrentWriters_jmhTest.java:86)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:565)
at org.openjdk.jmh.runner.BenchmarkHandler$BenchmarkTask.call(BenchmarkHandler.java:527)
at org.openjdk.jmh.runner.BenchmarkHandler$BenchmarkTask.call(BenchmarkHandler.java:504)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:328)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:545)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:328)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1090)
java.lang.IndexOutOfBoundsException: Index 1002 out of bounds for length 1002
at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:100)
at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
at java.base/java.util.Objects.checkIndex(Objects.java:365)
at java.base/java.util.ArrayList.remove(ArrayList.java:552)
at java.base/java.util.Collections$SynchronizedList.remove(Collections.java:2753)
at com.ankurm.cow.WriteThroughputBenchmark.addRemove_fourConcurrentWriters(WriteThroughputBenchmark.java:68)
at com.ankurm.cow.jmh_generated.WriteThroughputBenchmark_addRemove_fourConcurrentWriters_jmhTest.addRemove_fourConcurrentWriters_thrpt_jmhStub(WriteThroughputBenchmark_addRemove_fourConcurrentWriters_jmhTest.java:147)
at com.ankurm.cow.jmh_generated.WriteThroughputBenchmark_addRemove_fourConcurrentWriters_jmhTest.addRemove_fourConcurrentWriters_Throughput(WriteThroughputBenchmark_addRemove_fourConcurrentWriters_jmhTest.java:86)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
at java.base/java.lang.reflect.Method.invoke(Method.java:565)
at org.openjdk.jmh.runner.BenchmarkHandler$BenchmarkTask.call(BenchmarkHandler.java:527)
at org.openjdk.jmh.runner.BenchmarkHandler$BenchmarkTask.call(BenchmarkHandler.java:504)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:328)