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Why My Java Program Is So Slow?

Why My Java Program Is So Slow?# Java - 爪哇娇娃

b*92008-06-28 07:06

1 楼

Hi,
I rewrote a c++ program to java program. Both syntax and results are the
same. But java program is very slow. c++ is 40 seconds, but java is 800
seconds. Does anyone know the problem and how to improve my java program?
Thanks.
Bejamin

e*e2008-06-28 07:06

2 楼

Post your code here, maybe ppl can tell

【在 b*******9 的大作中提到】

: Hi,
: I rewrote a c++ program to java program. Both syntax and results are the
: same. But java program is very slow. c++ is 40 seconds, but java is 800
: seconds. Does anyone know the problem and how to improve my java program?
: Thanks.
: Bejamin

b*92008-06-28 07:06

3 楼

Thank emote's reply. But the code is too long to post here.I hopt to get
common ideas like environment, compiling and runing options to improve speed.

【在 e***e 的大作中提到】

: Post your code here, maybe ppl can tell

j*o2008-06-28 07:06

4 楼

What type of program is that?
How did you make the conversion?
What kind of hardware/OS?
Do you have a lot of I/O access?

【在 b*******9 的大作中提到】

b*92008-06-28 07:06

5 楼

Thanks, Jojomojo.
his program reads a 压缩 file, then 解压 it.
Only change is to change c++ point to java array. Put many c++ classes and
method to one java class and one method (does this cause speed problem?).
Run on Linux.

【在 j******o 的大作中提到】

: What type of program is that?
: How did you make the conversion?
: What kind of hardware/OS?
: Do you have a lot of I/O access?

m*t2008-06-28 07:06

6 楼

All the copying between I/O buffers is probably killing it.
Try map the files into memory.

【在 b*******9 的大作中提到】

: Thanks, Jojomojo.
: his program reads a 压缩 file, then 解压 it.
: Only change is to change c++ point to java array. Put many c++ classes and
: method to one java class and one method (does this cause speed problem?).
: Run on Linux.