Microbenchmarks and playing around with JMH
Run this with:
mvn package
java -jar target/microbenchmarks.jar ".*ListBenchmarks.*(listAdd).*" -wi 2 -i 5 -f 1 -t 3Breaking that down:
| Fragment | Meaning |
|---|---|
| java -jar target/microbenchmarks.jar ".ListBenchmarks.(listAdd).*" | run the benchmarks in ListBenchmarks that have method names beginning with listAdd |
| -wi 2 | means 2 warm up iterations to overcome jvm startup inertia |
| -i 5 | means run 5 actual iterations |
| -f 1 | means run 1 fork |
| -t 3 | means run the benchmarks in 3 threads |
and get results like:
# Run progress: 75.00% complete, ETA 00:00:08
# Warmup: 2 iterations, 1 s each
# Measurement: 5 iterations, 1 s each
# Threads: 3 threads, will synchronize iterations
# Benchmark mode: Average time, time/op
# Benchmark: com.davidhagar.microbenchmarks.ListBenchmarks.listAddLinkedListWithPointer
# VM invoker: /Library/Java/JavaVirtualMachines/jdk1.7.0_51.jdk/Contents/Home/jre/bin/java
# VM options: <none>
# Fork: 1 of 1
# Warmup Iteration 1: 371507.392 ns/op
# Warmup Iteration 2: 372918.653 ns/op
Iteration 1: 370407.611 ns/op
Iteration 2: 369963.860 ns/op
Iteration 3: 373438.190 ns/op
Iteration 4: 367462.735 ns/op
Iteration 5: 377556.485 ns/op
Result: 371765.776 ±(99.9%) 14905.642 ns/op [Average]
Statistics: (min, avg, max) = (367462.735, 371765.776, 377556.485), stdev = 3870.948
Confidence interval (99.9%): [356860.134, 386671.418]
Benchmark Mode Samples Score Score error Units
c.d.c.Microbenchmarks.listAddArrayListWithIterator avgt 5 956.445 44.848 ns/op
c.d.c.Microbenchmarks.listAddArrayListWithPointer avgt 5 963.061 91.788 ns/op
c.d.c.Microbenchmarks.listAddLinkedListWithIterator avgt 5 3122.704 1249.198 ns/op
c.d.c.Microbenchmarks.listAddLinkedListWithPointer avgt 5 362507.678 22396.165 ns/op