Re: 8 queens problem in Oforth

From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.lang.forth
Subject	Re: 8 queens problem in Oforth
Date	2015-03-23 15:56 -0700
Organization	A noiseless patient Spider
Message-ID	<87y4mn727h.fsf@jester.gateway.sonic.net> (permalink)
References	(9 earlier) <menl66$ade$1@dont-email.me> <87pp808se2.fsf@jester.gateway.sonic.net> <menqmi$q1t$1@dont-email.me> <87lhio8iai.fsf@jester.gateway.sonic.net> <2015Mar23.123414@mips.complang.tuwien.ac.at>

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anton@mips.complang.tuwien.ac.at (Anton Ertl) writes:
>>    derivative f x = (f (x+h) - f x) / h where h = 0.00001
>>    newton_step f x = x - (f x / f' x) where f' = derivative f
>>In Forth, this approach would probably be less convenient.
> Why do you think so?  In this case, you get an additional derivative
> definition for every word for which you want a derivative function,
> i.e., a constant factor overhead.  Not really a problem.

The derivative functions are per call, not per word.  E.g. if I call
sqrt(3), it creates the new function f(x)=x**2 - 3 and gives it to the
Newton solver, which calls the derivative HOF to create another new
function that is a numerical approximation of f'(x) = 2*x, so two new
functions were created.  Then if I call sqrt(5), it creates two more new
functions, and if my program computes a million square roots (not that
unusual), it ends up creating 2 million new functions (it can't tell
that the derivative functions are about the same for all of them).  It's
not optimized but it's mathematically expressive/convenient, and as you
say it's a constant factor overhead in computing time.  However, in a
non-GC'd system, creating 2 million new functions and leaving them
around is linear memory bloat, not good.  Therefore a less convenient
approach is probably required.

Better examples are in the Hughes paper that I linked in another post
just now.

> <http://soton.mpeforth.com/flag/jfar/vol4/no4/article6.pdf>...  I ran
> this code on a Commodore 64 with about 30KB of free memory, and I
> could run all the examples from the paper, and did not really feel
> memory-constrained in my own experiments: I only ran into the memory
> limitation when I did things that I designed to run into the memory
> limitation.

The paper says the program used 17k of memory to compute 6
factorial=720.  I think practical use of those methods will tend to
involve more computation and bigger numbers, so GC is needed.

>>The quotation doesn't know if it might be called more than once or what
>>else might want to use its args, against the usual convention that
>>functions should consume their parameters.
> What makes you think that the quotation does not heed this convention?

Because if it is called more than once and consumes its parameters, the
parameters are gone after the first call.  Am I missing something?

Thread

8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-19 07:53 +0000
  Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-19 08:58 -0700
    Re: 8 queens problem in Oforth Doug Hoffman <glidedog@gmail.com> - 2015-03-20 08:16 -0400
      Re: 8 queens problem in Oforth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-21 10:11 +0000
        Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-21 03:45 -0700
          Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-21 14:14 -0700
            Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-21 14:28 -0700
              Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-21 14:38 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-21 15:15 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-21 18:23 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-22 03:03 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 14:04 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-22 16:34 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 21:49 -0700
                Re: 8 queens problem in Oforth Raimond Dragomir <raimond.dragomir@gmail.com> - 2015-03-23 00:05 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-23 21:43 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-24 04:13 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-23 00:17 -0700
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-21 19:47 -0700
                Re: 8 queens problem in Oforth franck.bensusan@gmail.com - 2015-03-22 08:41 -0700
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 13:37 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-22 18:13 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 13:55 -0700
                Re: 8 queens problem in Oforth "Alex McDonald" <blog@rivadpm.com> - 2015-03-22 21:08 +0000
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 14:39 -0700
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 14:50 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-22 22:58 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 15:13 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-23 01:03 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 17:33 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-23 02:37 +0100
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 20:53 -0700
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 21:11 -0700
                Re: 8 queens problem in Oforth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-23 11:34 +0000
                Re: 8 queens problem in Oforth albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-03-23 19:31 +0000
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-23 15:56 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-24 00:38 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-23 19:08 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-30 05:02 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-30 05:08 -0700
                Re: 8 queens problem in Oforth "Alex McDonald" <blog@rivadpm.com> - 2015-03-30 15:36 +0100
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-23 16:46 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-23 15:32 -0700
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-23 23:48 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-23 16:14 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 17:54 -0700
                Re: 8 queens problem in Oforth "Alex McDonald" <blog@rivadpm.com> - 2015-03-22 23:09 +0000
                Re: 8 queens problem in Oforth Bernd Paysan <bernd.paysan@gmx.de> - 2015-03-22 22:11 +0100
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-22 14:48 -0700
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 15:11 -0700
                Re: 8 queens problem in Oforth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-23 11:29 +0000
                Re: 8 queens problem in Oforth albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-03-23 12:20 +0000
                Re: 8 queens problem in Oforth hughaguilar96@gmail.com - 2015-03-22 14:21 -0700
                Re: 8 queens problem in Oforth Coos Haak <chforth@hccnet.nl> - 2015-03-22 22:30 +0100
            Re: 8 queens problem in Oforth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-23 14:45 +0000
              Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-23 14:53 -0700
                Re: 8 queens problem in Oforth "Elizabeth D. Rather" <erather@forth.com> - 2015-03-24 09:16 -1000
                Re: 8 queens problem in Oforth Paul Rubin <no.email@nospam.invalid> - 2015-03-24 12:40 -0700
                Re: 8 queens problem in Oforth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-03-30 12:24 +0000
          Re: 8 queens problem in Oforth Coos Haak <chforth@hccnet.nl> - 2015-03-21 22:27 +0100
  Re: 8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-19 20:31 +0000
  Re: 8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-19 20:35 +0000
  Re: 8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-21 17:31 +0000
    Re: 8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-21 20:50 +0000
    Re: 8 queens problem in Oforth "WJ" <w_a_x_man@yahoo.com> - 2015-03-21 21:52 +0000

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