Java code is running faster than equivalent C++ code

I did not believe it at first, but it seems true: a fuzzy matching algorithm that I wrote is running faster implemented in Java than in C++ (about 5% faster).

A few caveates: the Java code is part of a large very long running server process so Hotspot has had a lot of time to optimize the code. Also, about 90% of the runtime of the entire system is in the small section of code that I reimplemented in C++ - this is about as good a scenario for Hotspot optimization than you could hope for. The particulars:

Java JVM: J2RE 1.4.2 IBM build for PowerPC.
C++: GNU g++ used with -O3

The code uses a packed block of 8 bit byte values that is about 4 megabytes. There is no code in this algorithm that could be optimized away: just some nested loops comparing byte values and performng a few sums.

Java on the server is not slow! This is for a customer project, and to get better performance I was willing to recode the whole thing in C++ if there had been an appreciable performance gain - obviously I won't do that now :-)

Comments

Popular posts from this blog

Ruby Sinatra web apps with background work threads

Time and Attention Fragmentation in Our Digital Lives

My Dad's work with Robert Oppenheimer and Edward Teller