Re: For performance, fix the Java program

Isaac Gouy wrote:
1) Over the past 3 or 4 days, people have said what's wrong with the
way you're producing output in Java, and suggested what you should do
instead. Is it that you don't know enough Java to follow their
suggestions and fix the program?
So far the only language that has come close to running as fast as the C is the Ocaml version and since then I have found other ways to speed up the C version. Just as I have posted the Ruby and Ocaml version if any certified Java expert cares to show me how it should be done (*cough* Charles O Nutter *cough*) then I will be happy to time it and check the output and report the results. That way we can get away from all this stupidity like the fact that I didn't use the correct naming convention. Which we all know hugely affects performance. But remember that the timings will be based on a program that produces output.
A couple of days ago single measurements on my machine gave
0.820s user+sys, gcc -pipe -Wall -O3 -fomit-frame-pointer
-funroll-loops -march=pentium4
4.444s user+sys, sun-jdk-1.5.0.07

Simply writing Java that converts the double-byte Unicode Java
outputStrings to single-byte /once/ instead of everytime there's a
print statement, and following the usual Java pattern of wrapping
output with a BufferedOutputStream, reduces that to

1.396s user+sys, sun-jdk-1.5.0.07

Yesterday I emailed you another version of your Java generating Perl
script that fixes those print problems, the output matches the C
program output.
If it was the email I replied to yesterday then reason that it got close to the speed of the C version was because it didn't do any output. Once I put the output back in it was only around 5 seconds faster than my own Java version and around 15 seconds slower than the C version. Hardly encouragement to drop C and pursue Java. Remember I am running the program to get the output.

2) If this is an application, and it has to produce output, and it has
to produce output for something larger than 6x6, then I think you need
a better algorithm.

You've mentioned the 5x5 C program took 2.473s, and the 6x6 took 9900s
- at that rate might we expect 7x7 in 15 months?
Actually the real problem is the amount of disk space I need to store the output. 6 x 6 resulted in 32Gb of output. The 7 x 7 will probably eat my hard disk well before it completes. I'm not sure that the 1Tb I have will be enough so I am looking at removing the rotational and mirrored versions of the grids from the output.


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