[Rd] problem in contour/contourLines (PR#9205)

Prof Brian Ripley ripley at stats.ox.ac.uk
Tue Sep 5 22:50:34 CEST 2006

It says

/* maximal number of line segments of one contour segment:
 * for preventing infinite loops -- shouldn't be needed --> warning */
#define MAX_ns 25000

so it would be very helpful to have a reproducible example.  Please also 
let us have exact details of how you compiled R (CPU, compiler versions, 
optimization level ...).

I have tracked a couple of things like this down to extended floating 
point issues on ix86 chips, so it may very well be that this is an issue 
of stopping an infinite loop.

(25000 segments is very large: a space filling graph on a 50x50 grid only 
needs about that many.)

On Tue, 5 Sep 2006, dheide at nld.ds.mpg.de wrote:

> Full_Name: Dominik Heide
> Version: 2.3.1
> OS: Linux (Suse 9.3)

On which CPU?

> Submission from: (NULL) (
> The contour functions has sommewhere (I think in .../main/plot3d.c) a 
> maximum number of line segments that is set using a define. The contour 
> line in my data too long for this and therefore not correct analysed (I 
> get the message 'contour(): circular/long seglist -- bug.report()!'). 
> Since I can't analyse my data right now, it's mybe better to give the 
> maximum seg-number as an option ?!

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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