[jdom-interest] Toward beta 9

[Rolf Lear]

How serious are people about performance in Verifier?

Using a relatively random input source (the characters in various Jars), I
can get a 500% - 1000% performance improvement in Verifier.

This is relatively simple, and "just as logical" as the existing verifier.

Have a look at the attached code, it is a "new" Verifier, with a main method
which has a relatively clunky, but effective performance test comparison
between the existing checks, and the proposed checks.

On my linux box I am getting performance improvements from 5.6 ms/10000
chars to 0.7ms/10000 chars. I know that the numbers are rough, but people
with profilers may be able to substantiate them better.

The basic principal is to build a bitmask representing all the valid
letters/combinations. The bitmask has 0xffff+1 bits, i.e. is 8K (relatively
small), and there is 1 for each "test". I have done only the isXMLLetter,
and isXMLCombiner. The pre-processing overhead is relatively small, (on my
box I measure 23ms).

Have a look-see, and tell me if I am barking up the wrong tree. I haven't
neatened up the code too much, but the principal seems good.

I have been running:

ant package
java -cp build/jdom.jar org.jdom.Verifier 5 lib/*.jar

and getting results:

Building lettermask
Done in 22ms.
Building combinationmask
Done in 0ms.
OLD Iteration lib/ant.jar count 0 took 6.93ms/10000 chars, counted 176182
trues in 732481 characters .
NEW Iteration lib/ant.jar count 0 took 0.76ms/10000 chars, counted 176182
trues in 732481 characters .
OLD Iteration lib/ant.jar count 1 took 5.61ms/10000 chars, counted 176182
trues in 732481 characters .
NEW Iteration lib/ant.jar count 1 took 0.76ms/10000 chars, counted 176182
trues in 732481 characters .
OLD Iteration lib/ant.jar count 2 took 5.66ms/10000 chars, counted 176182
trues in 732481 characters .
NEW Iteration lib/ant.jar count 2 took 0.76ms/10000 chars, counted 176182
trues in 732481 characters .
OLD Iteration lib/ant.jar count 3 took 5.69ms/10000 chars, counted 176182
trues in 732481 characters .
NEW Iteration lib/ant.jar count 3 took 0.76ms/10000 chars, counted 176182
trues in 732481 characters .
OLD Iteration lib/ant.jar count 4 took 5.61ms/10000 chars, counted 176182
trues in 732481 characters .
NEW Iteration lib/ant.jar count 4 took 0.76ms/10000 chars, counted 176182
trues in 732481 characters .
OLD Iteration lib/jaxen-core.jar count 0 took 5.34ms/10000 chars, counted
41039 trues in 160965 characters .
NEW Iteration lib/jaxen-core.jar count 0 took 0.86ms/10000 chars, counted
41039 trues in 160965 characters .
OLD Iteration lib/jaxen-core.jar count 1 took 5.34ms/10000 chars, counted
41039 trues in 160965 characters .
NEW Iteration lib/jaxen-core.jar count 1 took 0.8ms/10000 chars, counted
41039 trues in 160965 characters .
OLD Iteration lib/jaxen-core.jar count 2 took 5.34ms/10000 chars, counted
41039 trues in 160965 characters .
NEW Iteration lib/jaxen-core.jar count 2 took 0.8ms/10000 chars, counted
41039 trues in 160965 characters .
OLD Iteration lib/jaxen-core.jar count 3 took 5.34ms/10000 chars, counted
41039 trues in 160965 characters .
NEW Iteration lib/jaxen-core.jar count 3 took 0.8ms/10000 chars, counted
41039 trues in 160965 characters .
OLD Iteration lib/jaxen-core.jar count 4 took 5.34ms/10000 chars, counted
41039 trues in 160965 characters .
NEW Iteration lib/jaxen-core.jar count 4 took 0.8ms/10000 chars, counted
41039 trues in 160965 characters .
........


Rolf


-----Original Message-----
From: Elliotte Rusty Harold [mailto:elharo at metalab.unc.edu]
Sent: Thursday, April 10, 2003 7:54 AM
To: jdom-interest at jdom.org
Subject: Re: [jdom-interest] Toward beta 9


At 10:55 PM -0700 4/9/03, Philip Nelson wrote:
>Has anybody tried this approach?
>
>create a package protected or inner subclass of DefaultJDOMFactory in
>SAXBuilder.  Then in the factory, for example...
>
>     private class NoCheckText extends Text
>     {
>        public void noCheck(String text) {
>           value = text;
>        }
>     }
>     public Text text(String text) {
>         NoCheckText t = new NoCheckText();
>         t.noCheck(text);
>         return (Text) t;
>     }


That looks like it might actually work without causing too many 
problems or further complicating the API, though it does depend on 
those protected, do-nothing, no-args constructors that I wish we 
didn't have.
-- 

+-----------------------+------------------------+-------------------+
| Elliotte Rusty Harold | elharo at metalab.unc.edu | Writer/Programmer |
+-----------------------+------------------------+-------------------+
|           Processing XML with Java (Addison-Wesley, 2002)          |
|              http://www.cafeconleche.org/books/xmljava             |
| http://www.amazon.com/exec/obidos/ISBN%3D0201771861/cafeaulaitA  |
+----------------------------------+---------------------------------+
|  Read Cafe au Lait for Java News:  http://www.cafeaulait.org/      |
|  Read Cafe con Leche for XML News: http://www.cafeconleche.org/    |
+----------------------------------+---------------------------------+
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