Arity Performance on Mobile Phone vs. Desktop Computer
Thursday, March 27th, 2008I’m so happy I’m blogging again!
So, everybody knows already that I am the author of the Arity Arithmetic Engine, a nice little open-source library for evaluating arithmetic expressions. In this library I put quite some attention on the elegant and minimal code, and on performance. The functionality is mainly split in two parts: compiling an expression (takes a string and returns a Function object), and evaluating the Function.
For example, compiling the string “g(x)=x^2″ produces a Function instance. Calling eval(5) on this function returns 25. These two operations (compilation and evaluation) are separated because you typically compile an expression once, but evaluate it many times (for example when plotting the graph of a function).
On a desktop computer, Arity can do about 50,000 compilations/second, and about 1,000,000 evaluations/second. So the compilation is about 20 times slower than the evaluation.
Why is the compilation so slow? well, you may be surprised, but the bottleneck during compilation is the parsing of a double value from a string (using the java.lang.Double.parseDouble(String)).
And Double.parseDouble() is not only slow, it also does quite some memory allocations (which again result in slowness when the GC is invoked to collect that memory).
One key advantage of the Arity library is that it compiles not only on JavaSE (desktop Java), but also on JavaME/MIDP (mobile Java). So last weekend I decided to measure its performance on my mobile phone (a modest Nokia 6300). I wrote a tiny midlet for the benchmark, and the result is:
On the mobile phone, Arity does about 500 compilations/second, and about 10,000 evaluations/second. So the 20 times factor between compilation and evaluation speed is the same as on desktop.
And the key information, the mobile phone is about 100 times slower than the desktop computer (from Arity’s point of view).
Still, 10,000 evaluations/second on the mobile phone is not bad, I am quite happy with this performance.
PS: go check out Arity: http://arity.googlecode.com/