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Re: setjmp, longjmp, parser state, threads

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"Morten W. Petersen" <morphex@gmail.com> writes:
<snip>
> I'm writing an XML parser, which will also be built to support
> threads.

That's a good idea.  Pretty much all utility code should aim to be
thread safe or thread aware.  (I'm not being sarky -- I know that may
not be what you mean by "support" but it will be a valuable consequence
of any consideration of threads.)

> Now, I've been looking at bit at threads, parser state, setjmp and
> longjmp.
>
> Threads will be an important optional feature to minimize the amount of
> time it takes to parse an XML file.

This is not an obvious fact that you can just assert.  You may have some
evidence for it, but if not I think you should try it out first as I
suggest below

<snip>
> Am I right in thinking that since the program will use threads at some
> point, it is a good idea to have a parser object instead of a setjmp /
> longjmp thing?

You should have a parse object to reflect the state of the parse (error
flags included) because that's the right thing to do anyway.  And you
should generally avoid setjmp and longjmp unless they are forced on you
(i.e. they appear to be the only way out of some serious design
problem).  Support for threading does make the arguments for a parse
object and against setjmp/longjmp a bit stronger, but it's not the
reason to make that choice.

As for using threads for parsing XML, I suggest you try an experiment.
Write a throw-away threaded program the builds a tree structure from
some text input (you can invent your own to be favourable to threaded
parsing) and see if you can indeed make it as fasted than a non-threaded
version.  You've decided that threads will make parsing faster, but I
find that hard to believe though I'd love to see that preconception
overturned.

Such an experimental program would teach you a lot about writing
threaded code (I think you are new to that from what you've written) and
it would force you to think about how parsing can be broken up into
suitable work units (which it one of the barriers I have to thinking
that there is any value in using threads).  Both of those would be
valuable to you even if the code is eventually thrown away.

But the big point is that either you'll learn that threads are not a
good match to this problem (and that's a big win for you if it's true),
or I'll learn that I've got an unhelpful mental picture model of what
threads can do (that's less of a win for you, but you'll have done me a
service).  Surely all of that is worth a short experiment?

<snip>
-- 
Ben.

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setjmp, longjmp, parser state, threads "Morten W. Petersen" <morphex@gmail.com> - 2015-07-27 20:50 +0200
  Re: setjmp, longjmp, parser state, threads Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-28 00:22 +0100
    Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state, threads] Jeff Higgins <jeff@invalid.invalid> - 2015-07-27 21:00 -0400
      Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state,   threads] Ian Collins <ian-news@hotmail.com> - 2015-07-28 13:57 +1200
        Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state,   threads] Jeff Higgins <jeff@invalid.invalid> - 2015-07-27 22:13 -0400
          Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state,     threads] Ian Collins <ian-news@hotmail.com> - 2015-07-28 17:12 +1200
            Re: OT - XML Parallel Parsing Jeff Higgins <jeff@invalid.invalid> - 2015-07-28 09:46 -0400
          Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state, threads] "Morten W. Petersen" <morphex@gmail.com> - 2015-07-28 10:07 +0200
            Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state, threads] raltbos@xs4all.nl (Richard Bos) - 2015-07-28 09:28 +0000
              Patents, was [Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state, threads]] "Morten W. Petersen" <morphex@gmail.com> - 2015-07-28 11:41 +0200
                Re: Patents, was [Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state, threads]] Stephen Sprunk <stephen@sprunk.org> - 2015-07-28 20:53 -0500
                Re: Patents, was [Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state, threads]] "Morten W. Petersen" <morphex@gmail.com> - 2015-07-29 05:15 +0200
                Re: Patents, was [Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state, threads]] Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-07-28 22:34 -0600
      Re: OT - XML Parallel Parsing, was [Re: setjmp, longjmp, parser state, threads] Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-07-28 03:06 +0100
    Re: setjmp, longjmp, parser state, threads "Morten W. Petersen" <morphex@gmail.com> - 2015-07-28 10:44 +0200
      Re: setjmp, longjmp, parser state, threads Ian Collins <ian-news@hotmail.com> - 2015-07-28 22:14 +1200
        Re: setjmp, longjmp, parser state, threads "Morten W. Petersen" <morphex@gmail.com> - 2015-07-28 15:17 +0200
      Re: setjmp, longjmp, parser state, threads Jeff Higgins <jeff@invalid.invalid> - 2015-07-28 08:35 -0400
      Re: setjmp, longjmp, parser state, threads James Kuyper <jameskuyper@verizon.net> - 2015-07-28 10:29 -0400
        Re: setjmp, longjmp, parser state, threads "Morten W. Petersen" <morphex@gmail.com> - 2015-07-28 16:39 +0200
  Re: setjmp, longjmp, parser state, threads jadill33@gmail.com - 2015-07-28 06:47 -0700
    Re: setjmp, longjmp, parser state, threads "Morten W. Petersen" <morphex@gmail.com> - 2015-07-28 16:56 +0200
      Re: setjmp, longjmp, parser state, threads Noob <root@127.0.0.1> - 2015-07-28 18:04 +0200
      Re: setjmp, longjmp, parser state, threads jadill33@gmail.com - 2015-07-28 10:53 -0700
        Re: setjmp, longjmp, parser state, threads "Morten W. Petersen" <morphex@gmail.com> - 2015-07-29 04:59 +0200
  Re: setjmp, longjmp, parser state, threads Bartc <bc@freeuk.com> - 2015-07-28 16:29 +0100

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