Hello Michael,

Everything works so far, with the exception of UNION, which technically works fine but exposes an infinite loop bug which was being broken by a stack overflow before.

The regex: (((((boy)|(girl))[0-1][x-z]{2})?)|(man|woman)[0-1]?[y|n])*
With Target: boy0xxwoman1ygirl1xyman

Loops forever (the ending is invalid, needs [0-1]?[y|n] ). Well, forever being 'until you run out of memory'. I didn't notice this until I set my memory back to a reasonable size, as I had the -Xmx flag set to a GB earlier for some playing.

So the options are
a. ) Fix it. Being a serious edge case, I'm thinking this isn't really worth the risk. More bluntly, it would take me far more time than I want to spend on it to become comfortable with any fix I might produce.

b. ) Ignore the case (let the system die of OOM *eventually*, recognizing your CPU will be pegged for a while before this happens)

c. ) Throw an exception if the stack depth gets to some crazy level (a million deep, for instance), perhaps adding a System variable to set the allowable depth.

d. ) Other?


For reference, using the standard JVM (no flags, 64MB heap space, IIRC), I can check the DNA string appended to itself ~425 times before reaching a depth of a million stack elements. DNA_STRING is 2273 characters long.

I run out of memory (heap space) around 650*DNA_STRING, with a depth of 1,477,450. (the string being 1,477,450 characters long... big shock).

DNA String runs out of memory very quickly, whereas the above regex is pretty slow about it because it pushes and pops a huge number of stack items, *eventually* achieving an overflow. The DNA string pushes items until it gets an answer, then backs out in the same order.

Also, and oddly, the 'CAPTURE' option doesn't get hit a single time in the 7000 or so regex tests provided by the W3C group. Testing it with the full suite, which takes a painfully long time.

I'm moving into optimization mode now that the regex tests check out; once I hear back as to how the group wants the new bug handled, I'll implement it and post the code for review.

Oh, did you want the Test Suite code I had to implement? There's a lot of generics code in it, and it's incredibly hackish, but it's free to whoever wants it. It is by no means robust nor complete. IntelliJ has an 'Export to Eclipse' setting for modules, if that interests you.

Cheers,
--
Geoff M. Granum
Portland, Oregon

On Mon, 25 Jun 2007 05:43:16 -0700, Michael Glavassevich <[EMAIL PROTECTED]> wrote:

Hi Geoff,

The W3C test suite contains many regex tests, particularly this large
bucket [2] of tests contributed last year. That should give you a pretty
good selection though beware that some of the tests are invalid. The known
problems are documented in the W3C's Bugzilla here [3].

As for the code, one thing that may not be obvious is that it needs to be
thread-safe. This is because the RegularExpression objects are cached in
the schema grammar which could be shared with several parsers and
validators. To avoid having many large synchronized blocks, the matching
code keeps its state local to the call stack. Hoping that's the approach
you've been taking.

Thanks.

[1] http://www.w3.org/XML/2004/xml-schema-test-suite/index.html#releases
[2]
http://dev.w3.org/cvsweb/XML/xml-schema-test-suite/2004-01-14/xmlschema2006-11-06/msMeta/Regex_w3c.xml
[3]
http://www.w3.org/Bugs/Public/buglist.cgi?query_format=specific&order=relevance+desc&bug_status=__open__&product=XML+Schema+Test+Suite&content=

Thanks.

Michael Glavassevich
XML Parser Development
IBM Toronto Lab
E-mail: [EMAIL PROTECTED]
E-mail: [EMAIL PROTECTED]

"Geoff M. Granum" <[EMAIL PROTECTED]> wrote on
06/25/2007 04:15:27 AM:

(If you don't care about the particulars, but have some Regex's you can
contribute, jump to the code bit. Thanks)

I have two implementations to test; one is a (somewhat) naive linked
list
stack manager, the other is (as yet) still recursive.

The former works, but I put it together as a proof of concept and don't
trust it much. Fifty-two return points in one method is a tad much.
Implemented as a raw java.util.Stack is ten times as slow as the
original,
and creating a private static LocalStack class as a LinkedList is twice
as
slow.

Though, 10K runs of the first thousand chars of the two example regex
patterns take ~1.2 and 2.6 seconds, respectively. So .12ms and .26ms per

run. I'm rather set against ANY performance decrement, or I'd have just
verified that code and moved on.

The latter implementation is a refactor of the method to a single point
of
exit. THAT goal is working, now I have to make sure that I can add
values
to an internal stack manager without blowing away any state -- some of
the
CASE statements are a mite obtuse, and I don't like using breaks much.
Breaks also seem to affect the ability of the optimizer to do its job,
as
the last CASE I modified (op.CLOSURE) gave a 10% performance boost
without
it. Although I'm suspicious, as it's late and now the stack overflows
somewhat (ok, a lot) earlier than before. I did add a number of
variables,
so it's possible I made no mistake in the logic (I'd better not have!).

--- The request part ---

Regardless of the final form, I need to populate a test library:

I have a few regular expressions lying around, and I figure I'll parse
in
a few of my XML files and modify the RegularExpression class to dump
anything it sees to a file... I still doubt I'd have more than 20, and
none of them shockingly complex.

So if you could send me your favorite regular expressions, along with a
couple of stings to match them against (some pass, some fail, but
indicate
which), it would be a big help.

Even better, if you could format them like this sample:

testCases.add(new TestCase(
   "Overall description",
   "Your Regex Pattern",
   new SubCase("A description", shouldPass, "matchString" ),
   new SubCase("A description2", shouldPass, "matchString2" ),
   ... more SubCases ...
));

I would be able to paste them straight into the unit test and run them.
The SubCase argument uses varArgs, so add as many as you want/will. Feel

free to add your 'contributed by:' to the overall description area for
credit... Though I'd remind you not to include a parsable (or any, lest
random-someone ask you for help later) e-mail address on this list, as
it
is public and archived.

My own direct e-mail address is (my first name @ my last name).biz. And
if
someone has written a parser for THAT, they can have it.

The more complex your tests the better, for the beat down. Tailored
regex's would be grand for focused testing (e.g. the simplest lookahead,

lookbehind, singleline, multiline, etc). But I figure that's asking for
real work.

Also, or instead, if you have a 'regular expression rich' schema and
conforming xml file that you can send (think 'might become public'), I
should be able to parse those out without much trouble.

And yes (obviously), my test library uses 1.5 features... I'll convert
it
if the changes are approved for commit. Keeps me sane.

Of course the changes to RegularExpression are using JDK 1.3 as a
target,
as that is the lowest I've available. My memory of the differences
between
1.2 and 1.3 are fuzzy, but I don't think anything I'm using has changed
since 1.0. My only real concern is that my JVM has a better optimizer
and
could be hiding poor performance that I induce.


Thanks much,
--
Geoff M. Granum
760-534-1636
Portland, Oregon

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