Stefan Krause.blog()

In one of the comments regarding my Java vs. C benchmark Dmitry Leskov suggested including Excelsior JET. JET has an ahead of time compiler and is known to greatly reduce startup time for java applications. I’ve kept an eye on JET since version 4 or so and while the startup time has always been excellent the peek performance of the hotspot server compiler was better. With JET 5 performance for e.g. scimark has improved greatly so I decided to rerun the benchmark for JET 5 and JET 6 beta 2. JET 6 beta 2 is currently available on windows only and thus the tests were run under Windows Vista, JET 5 (and all other VMs) ran under Ubuntu. I also benchmarked JET 5 on Windows to check if there’s a large OS-related difference, but the results were within 2.4% (still a t-Test showed a significant difference). As a simplification I decided to publish only the Ubuntu JET 5 results. Nevertheless I’ll update the results when beta 3 becomes available for linux.

Another interesting VM is Apache Harmony. It is designed to be a complete open source JDK and it received a lot of attention when it started (and it became pretty quite nowadays). It started before Sun decided to open their JDK under the GPL, so if nothing else harmony was in my opinion one of the reasons that we have Sun’s openjdk project now. Harmony’s VM is based on a intel donation so that alone makes benchmarking interesting. Of course Harmony is still in the early stages and it would be almost a miracle if Harmony 1.0 could beat the performance of Sun’s JDK.

The third VM is also an ahead of time compiler. GCJ is a java frontend for the GCC and thus might produce code roughly identical to GCC. There isn’t too much publicity for GCJ despite its effort to become a really usable JVM. Combined with the GIJ interpreter and the gcj-dbtool GCJ is able to compile even complex applications like eclipse. GCJ uses classpath as its underlying implementation of the JDK classes which means some parts of the JDK are still missing. I decided to use the Ubuntu gcc 4.3 snapshot as it turned out to work best on my PC. (more…)

Java’s performance is perceived rather differently depending on who you ask ranging from Java-is-faster-than-C to “java is 10x slower”.
Without actually running some benchmarks it’s hard to tell who is actually right and of course every benchmark will show different results and both sides have good arguments. I don’t know of any real world applications that has been ported from C to Java in such a way that statements about their relative performance are valid. So the only source I know are (micro-)benchmarks. Besides the well known Scimark and linkpack benchmarks there are some interesting benchmarks on the “computer language benchmark game” formerly known as the great language shootout. It has often been criticized for too short duration and including warmup times for JITs. Still I like those benchmarks since they are not classic microbenchmarks, but (almost) every benchmark tries to stress a certain set of language features and returns a well defined output.
To make it short: I decided to select four computational intensive, IO-less benchmark from the shootout. (more…)