• Post Reply
  • Bookmark Topic Watch Topic
  • New Topic

Again, Blackdown-JRE on iPAQ

 
Shuai Liu
Ranch Hand
Posts: 49
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Hi, Valentin
I just got Blackdown-JRE running on my H3765 with 64M RAM. I tried the IPAQDemo.jar. It was sooooo slow. Even the SimpleExample.jar, which is a simple frame with 3 buttons, took more than 10 seconds to show up. :Q
I remember you said that your 20000 line program takes only about 4 seconds. How did you do that? Should I do something to tune the performance?
Thanks a lot!
 
Valentin Crettaz
Gold Digger
Sheriff
Posts: 7610
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Sorry for the delay
Actually what I did is a little cheating. I just wrote the code in a manner that the user interface would appear very quickly so that the user doesn't get the impression that the device freezed. Then how fast the program runs once it is started is completely dependent on how you implemented it and what features you put in it. Actually, we are using java.math.BigInteger and lots of crypto stuff so we had to go native for those parts which speed things up. Moreover, there is no JIT compiler for ARM that I know of, so code cannot be optimized for that target architecture which may lead to serious performance penalties.
Here is an anecdote: I ran a profiler on both the development platform (x86) and the target platform (ARM) with my application and I performed exactly the same steps. Well, when I looked at the results, the execution on the iPaq needed 5 times more instruction executions than on the x86.
I can't really help, I know, but you should optimize your code before running it on the iPaq, that is the traditional performance tuning blabla, not create to many objects (reuse them), use String literals or intern newly created Strings, ... ( http://www.javaperformancetuning.com)
 
  • Post Reply
  • Bookmark Topic Watch Topic
  • New Topic