Is Fortran faster than C? - Programming Languages

On Sat, Jul 14, 2007 at 04:12:01AM -0800, glen herrmannsfeldt wrote:[color=blue]
>
> As far as I know, conservative GC is usual. It is well known
> in Java that GC will not recognize circular linked lists that
> can't be reached, such that one should assign null to break the
> list.[/color]

Eh? What do you mean? Garbage collectors can and do collect unreachable
circular data structures. IIRC, Sun's JVM uses some combination of
stop-and-copy and mark-and-compact, both of which are perfectly capable
of collecting unreachable circular data structures.

Regards,

Bob

--
"Beware of bugs in the above code; I have only proved it correct, but not
tried it."
-- Donald Knuth

Douglas Wells wrote:
(snip)
[color=blue]
> - C does, however, require that a data pointer fix within a
> variable of the form:
> unsigned char holder [sizeof (void *)];
> and the bits can be reliably copied in and out via the moral
> equivalent of:
> memcpy (holder, &dataptr, sizeof holder);
> memcpy (&dataptr, holder, sizeof dataptr);[/color]
[color=blue]
> Thus, it is possible for a conforming application program to copy
> the contents of a data pointer to an opaque container and copy
> that container outside of the process's address space (where it
> presumably can be neither located nor examined by the GC).[/color]
(snip)

In that case, the GC has to recognize that the pointer is
being copied out an never release that space.
[color=blue]
> Note that there are garbage collectors for C (the one by Hans Boehm
> likely being the most popular). Many of these GCs implement
> conservative collection algorithms: they perform program ****ysis
> (both static and dynamic) and, if they suspect that the address
> of a data block has become hidden from them, they will not garbage
> collect that data. I can't prove it, but I believe that for all
> of these GCs, there still exist various application actions that
> are legal C but which would confuse the GC (and therefore would
> cause improper run-time behavior).[/color]

As far as I know, conservative GC is usual. It is well known
in Java that GC will not recognize circular linked lists that
can't be reached, such that one should assign null to break the
list. Also, if one creates a large object in main that isn't
needed to assign null to the object reference. There are enough
cases where no GC can figure out that data won't be referenced,
such that the only way out is manual intervention.

The case above seems to require special code in memcpy to
recognize it.

-- glen

glen herrmannsfeldt wrote:[color=blue]
> As far as I know, conservative GC is usual. It is well known
> in Java that GC will not recognize circular linked lists that
> can't be reached, such that one should assign null to break the
> list. Also, if one creates a large object in main that isn't
> needed to assign null to the object reference. There are enough
> cases where no GC can figure out that data won't be referenced,
> such that the only way out is manual intervention.[/color]

Note that this is all completely wrong.

--
Dr Jon D Harrop, Flying Frog Consultancy
The OCaml Journal
[url]http://www.ffconsultancy.com/products/ocaml_journal/?usenet[/url]

On Jul 13, 3:11 pm, Dick Hendrickson <dick.hendrick...@att.net> wrote:[color=blue]
> Isaac Gouy wrote:[color=green]
> > On Jul 11, 11:00 am, Jon Harrop <j...@ffconsultancy.com> wrote:[color=darkred]
> >> Isaac Gouy wrote:
> >>> On Jul 7, 12:42 pm, Jon Harrop <j...@ffconsultancy.com> wrote:
> >>>> Deleting the Fortran entries from yourshootoutdoesn't make
> >>>> Fortran "unloved".
> >>> That's just malicious gossip - no one deleted Fortran entries from the
> >>>shootout.
> >> e.g. where's the Fortran ray tracer gone?[/color][/color]
>[color=green][color=darkred]
> >> --
> >> Dr Jon D Harrop, Flying Frog Consultancy
> >> The OCaml Journalhttp://www.ffconsultancy.com/products/ocaml_journal/?usenet[/color][/color]
>[color=green]
> > Next you'll be asking where your head has gone - it hasn't gone
> > anywhere.[/color]
>
> Er, um, maybe Jon could have phrased his question a little better, but
> isn't it obvious that he doesn't know where the program is? Why not
> simply tell him where to look?
>
> Dick Hendrickson[/color]


It's obvious that Jon has claimed "the Fortran implementations of the
ray tracer benchmark ... were all deleted. ... deleted by the shootout
maintainers..." [Jul 7, 3:18 pm] without making any attempt to show
that accusation has any basis in reality.

Jon continues to demand that I disprove his baseless claim - that's
just the wrong way around, it isn't for us to disprove claims that the
moon is made of green cheese, doing the work to disprove baseless
claims is just an encouragement.

I think Jon Harrop is a clever guy, I think he phrases his questions
carefully and I don't guess about his motivations ;-)

In article <1184433600.500366.205770@g12g2000prg.googlegroups.com>,
Isaac Gouy <igouy2@yahoo.com> wrote:
[color=blue]
>It's obvious that Jon has claimed "the Fortran implementations of the
>ray tracer benchmark ... were all deleted. ... deleted by the shootout
>maintainers..." [Jul 7, 3:18 pm] without making any attempt to show
>that accusation has any basis in reality.[/color]

It would be helpful if people would talk to each other instead of just
butting heads.

I don't see a ray tracer in the current benchmark list. Did there used
to be one? Was it deleted?

-- g

On Jul 14, 10:34 am, lind...@pbm.com (Greg Lindahl) wrote:[color=blue]
> In article <1184433600.500366.205...@g12g2000prg.googlegroups.com>,
> Isaac Gouy <igo...@yahoo.com> wrote:
>[color=green]
> >It's obvious that Jon has claimed "the Fortran implementations of the
> >ray tracer benchmark ... were all deleted. ... deleted by theshootout
> >maintainers..." [Jul 7, 3:18 pm] without making any attempt to show
> >that accusation has any basis in reality.[/color]
>
> It would be helpful if people would talk to each other instead of just
> butting heads.[/color]

None of this is news to Jon :-)

[color=blue]
> I don't see a ray tracer in the current benchmark list. Did there used
> to be one? Was it deleted?[/color]


To repeat [Jul 10, 5:58 pm] "...the fact is that we have programs for
41 obsolete problems in CVS, and we have been showing programs for the
same 19 active problems for about the last 2 years."

raytracer is one of those 41 obsolete problems, last shown in August
2005.

Aren't you going to ask if "the Fortran implementations of the ray
tracer benchmark ... were all deleted. ... deleted by the shootout
maintainers..." ?

Isaac Gouy writes:[color=blue]
> Aren't you going to ask if "the Fortran implementations of the ray
> tracer benchmark ... were all deleted. ... deleted by the shootout
> maintainers..." ?[/color]

Oh for Ghu's sake. This is obviously a private quarrel, as determined
you all are to make sure no outsiders can easily find out what you are
yakking about. So take this to a private mail. Or if you must go on
in public, at least get a grip and post some URLs where people - and
Harris - can judge for themselves without deciding from who is best at
throwing dirt.

There have been some interesting postings under this subject, but this
isn't it.

--
Regards,
Hallvard

I wrote:[color=blue]
> in public, at least get a grip and post some URLs where people - and
> Harris - can judge for themselves without deciding from who is best at
> throwing dirt.[/color]

Oops, Harrop of course. Sorry.

--
Regards,
Hallvard

In article <1184438369.259366.326410@g12g2000prg.googlegroups.com>,
Isaac Gouy <igouy2@yahoo.com> wrote:
[color=blue]
>Aren't you going to ask if "the Fortran implementations of the ray
>tracer benchmark ... were all deleted. ... deleted by the shootout
>maintainers..." ?[/color]

Well, no, but you did just explain Jon's complaint. I agree that Jon
is a butt-head (he's in my killfile and belongs in yours, too), but
you could have explained the obsolete program issue immediately
instead of being coy about it.

-- greg