[MPlayer-cvslog] r26723 - in trunk: Makefile av_opts.c av_opts.h

[Michael Niedermayer]

On Thu, May 15, 2008 at 12:30:14PM +0200, Diego Biurrun wrote:
> On Thu, May 15, 2008 at 04:10:07AM +0200, Michael Niedermayer wrote:
> > On Wed, May 14, 2008 at 07:15:59PM +0200, Diego Biurrun wrote:
> > > Not all people know what the GPL is and the text of the GPL may not come
> > > included with the source file in question.  Thus, information about
> > > where to get the licensing terms are useful.  Snail mail may seem
> > > somewhat anachronistic, but the GPL version 2 dates from 1991.  The GPL
> > 
> > actually i wonder if anyone ever did write them and ask for the license? :)
> > And how scaleable that would be if a significant number of users would have
> > done that ...
> 
> Just charge whatever costs this entails and the process becomes
> scalable enough in practice.

How can the FSF charge money if they receive letters with requests for the
license and a return snail mail address? Even if sending the reply letters
didnt cost them anything theres the work for handling it and the cost for
the paper.
Yes they could just inlcude a request for some payment in the letter but
lets assume all the return addresses where wrong, they never would receive
any payment ...

It only works because people are so honest / too lazy not to mailbomb them ;)


> 
> > > > -- 
> > > > 
> > > > Awnsering whenever a program halts or runs forever is
> > > > On a turing machine, in general impossible (turings halting problem).
> > > 
> > > undecidable
> > > 
> > > > On any real computer, always possible as a real computer has a finite number
> > > > of states N, and will either halt in less than N cycles or never halt.
> > > 
> > > semidecidable
> > > 
> > > What were you trying to say there?
> > 
> > exactly what i did say.
> > 
> > > Any particular instance of the
> > > halting problem is semidecidable, the general problem is not.
> > 
> > That exactly is false.
> > The problem is perfectly decideable in the general sense on any real
> > computer i could think of.
> 
> Imagine a (very simple) program that searches for an odd perfect number.
> Whether such a number exists or not is an open question.  If you let
> such a program run on any real computer, it could either
> 
> - output an odd perfect number or
> - run out of resources.
> 
> In the latter case, the question whether the program that searches for
> an odd perfect number halts or not has not been answered.

The error in your reasoning is the following:
"Imagine a (very simple) program that searches for an odd perfect number"

you assume here that such a program does exist.
While a naive program doing that will of course only be able to search
2^64 numbers, one using an arbitrary precission lib could search
2^bits_of_mem numbers. Thus really we only know how to write a
(very simple) program which searches for an odd perfect number < N. And that
is perfectly decideable.

It of course does not neccessarily awnser the mathematical question about
the existence of odd perfect numbers. But the reason why this is so is
because we do not know how to turn the mathematical question of the
existence of such a number into a program. Not that such a program would
exist and be semidecidable on any real computer.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Awnsering whenever a program halts or runs forever is
On a turing machine, in general impossible (turings halting problem).
On any real computer, always possible as a real computer has a finite number
of states N, and will either halt in less than N cycles or never halt.
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