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Re: Knight's tour

From: Doug Stewart
Subject: Re: Knight's tour
Date: Sun, 10 Feb 2019 06:53:09 -0500

On Sun, Feb 10, 2019 at 5:03 AM Simon Allen <address@hidden> wrote:
Hi Doug,

It has not been resolved.  The only other post I received was from Kai Ohlhus who tried it in both Octave and Matlab with the same error.  He opined that SpiralNumbering was missing and suggested I contact the author. It is clearly not a built-in Matlab function and so I am stuck. The author Daniël Karssen has done quite a lot of work in this area on 0EIS.  I have looked at his other contributions to see if he has used it elsewhere.  I have not found it.  I have no contact details for him and he has not left anyway to contact him in OEIS.  I know that programmers are not keen to try and modify someone else's program but I'm guessing that the missing module puts numbers in squares surrounding the knight from the knight's last position. I'm not quite sure how to do that quite apart from having no Matlab experience. So if there' is any light that you can throw on this it will be very welcome. I run a local Mathsjam group in Bexhill and Knight's Tours have been a topic of conversation from time to time.  One of our members was George Jellis who is probably the world expert on Knight's Tours but he had not come across this version.    I hope to talk about this new problem at our next Mathsjam on 19th February.  Whilst I am quite familiar with Knights tours and even played with them as a child when I found out about this particular problem on the Numberphile video  I paused it to think about what the likely outcome would be. It seemed to me that given an infinite board and the ability the knight to move to any one of eight squares that it would make a pretty pattern that would go to infinity. So it was a surprise that this is not the case.  So if there's any light you can throw on this to get the code going then please let me know.



I have written a function that fills a square array with the spiral numbers. as per
And I have written a function that if you give it a location in that array it finds the eight possible
knight move locations, and returns the smallest spiral number's location.

We still have to keep track of the location that have been visited, etc.

Are you interested in these. I will add some comments.

Doug Stewart 

PS keep Octave help in the loop.


On Sun, 10 Feb 2019 at 04:07, Doug Stewart <address@hidden> wrote:

On Wed, Feb 6, 2019 at 1:56 PM SimonAllen <address@hidden> wrote:
I am very new to Matlab and I am using Octave.  I am trying to get the Matlab
code that is is at to run.  It follows on from a
Numberphle video on Knight's tour.  I have already discovered that Matlab
paths do not like upper case or spaces in paths and filenames and I have
fixed that but in line 52 of the code there is this command

      xy2num = @(x,y) SpiralNumbering(x,y);

It is not referenced anywhere else.

Octave gives this error

error: 'spiralnumbering' undefined near line 52 column 25
error: called from
    knightstour>@<anonymous> at line 52 column 25
    knightstour at line 78 column 19
I am at the moment baffled.  Can anyone throw any light on this?

Did you get this to work yet?
I might be able to help you.


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