Warnings when compiling Delauney Triangulations

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Warnings when compiling Delauney Triangulations

Joern Ungermann
Hi all,

I am using CGAL for nearest neighbor interpolation in two and three
dimensions. The manual got me started well enough to implement both.
When compiling the code with gcc 4.2.1 *with* optimizations, I get
warnings with respect to some array subscripts being out of bounds.
2D and 3D Delauney triangulations set off different errors.

I attached example source files that I stripped down as much as I could
to generate the warnings. For each file, a log is contained that gives
the compilation command and the resulting output.

For 3D triangulation, simply inserting points seems to suffice, while
for 2D, the nearest neighbor calculation triggers it.

As we have a policy of treating warnings as errors this may prevent me
from using your nice library.

If somebody could assert that these warnings are (known) artifices of
gcc or even better how to get rid of them (without setting compiler
flags) I would be delighted.
I can easily supply further information about my system, if it would
help or do test compilations. As I am unfamiliar with the CGAL and I
have no clue what even triggers some of the warnings finding the cause
of this is a bit over my head.


Second, I'd like to do natural neighbor interpolations on the surface of
a sphere (i.e. earth surface being approximated as either sphere or
ellipsoid). Is something like this already contained within CGAL or easy
to add?

Thanks and kind regards,
Jörn

--
Jörn Ungermann

Dipl.-Mathematiker
ICG-1, Forschungszentrum Jülich
Tel.: +49 2461 61 1840




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Re: Warnings when compiling Delauney Triangulations

Sylvain Pion
Administrator
Jörn Ungermann wrote:

> I am using CGAL for nearest neighbor interpolation in two and three
> dimensions. The manual got me started well enough to implement both.
> When compiling the code with gcc 4.2.1 *with* optimizations, I get
> warnings with respect to some array subscripts being out of bounds.
> 2D and 3D Delauney triangulations set off different errors.
>
> I attached example source files that I stripped down as much as I could
> to generate the warnings. For each file, a log is contained that gives
> the compilation command and the resulting output.
>
> For 3D triangulation, simply inserting points seems to suffice, while
> for 2D, the nearest neighbor calculation triggers it.
>
> As we have a policy of treating warnings as errors this may prevent me
> from using your nice library.
>
> If somebody could assert that these warnings are (known) artifices of
> gcc or even better how to get rid of them (without setting compiler
> flags) I would be delighted.
> I can easily supply further information about my system, if it would
> help or do test compilations. As I am unfamiliar with the CGAL and I
> have no clue what even triggers some of the warnings finding the cause
> of this is a bit over my head.
We are aware of this warning.  Unfortunately, we have not succeeded in
getting rid of it (despite quite some time spent on it).
In my opinion, it is a GCC bug, with pretty high probability.


> Second, I'd like to do natural neighbor interpolations on the surface of
> a sphere (i.e. earth surface being approximated as either sphere or
> ellipsoid). Is something like this already contained within CGAL or easy
> to add?

Does the following fit the bill?
http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Interpolation/Chapter_main.html#Section_52.2

--
Sylvain Pion
INRIA Sophia-Antipolis
Geometrica Project-Team
CGAL, http://cgal.org/


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Re: Warnings when compiling Delauney Triangulations

Joern Ungermann

Am Donnerstag, den 13.11.2008, 13:59 +0100 schrieb Sylvain Pion:

> Jörn Ungermann wrote:
> > I am using CGAL for nearest neighbor interpolation in two and three
> > dimensions. The manual got me started well enough to implement both.
> > When compiling the code with gcc 4.2.1 *with* optimizations, I get
> > warnings with respect to some array subscripts being out of bounds.
> > 2D and 3D Delauney triangulations set off different errors.
> >
> > I attached example source files that I stripped down as much as I could
> > to generate the warnings. For each file, a log is contained that gives
> > the compilation command and the resulting output.
> >
> > For 3D triangulation, simply inserting points seems to suffice, while
> > for 2D, the nearest neighbor calculation triggers it.
> >
> > As we have a policy of treating warnings as errors this may prevent me
> > from using your nice library.
> >
> > If somebody could assert that these warnings are (known) artifices of
> > gcc or even better how to get rid of them (without setting compiler
> > flags) I would be delighted.
> > I can easily supply further information about my system, if it would
> > help or do test compilations. As I am unfamiliar with the CGAL and I
> > have no clue what even triggers some of the warnings finding the cause
> > of this is a bit over my head.
>
> We are aware of this warning.  Unfortunately, we have not succeeded in
> getting rid of it (despite quite some time spent on it).
> In my opinion, it is a GCC bug, with pretty high probability.
Thanks for the information!
>
> > Second, I'd like to do natural neighbor interpolations on the surface of
> > a sphere (i.e. earth surface being approximated as either sphere or
> > ellipsoid). Is something like this already contained within CGAL or easy
> > to add?
>
> Does the following fit the bill?
> http://www.cgal.org/Manual/3.3/doc_html/cgal_manual/Interpolation/Chapter_main.html#Section_52.2
>
I was looking more for the following: I need something similar to the
regular 2D triangulation/nearest neighbor identification function, but
working not on an infinite euclidean plane, but on (ideally part of) the
unit sphere (or something topographically similar). A one time high
setup cost is OK, but the interpolation needs to be reasonably fast as
we need to do that often.

Playing a bit with the example pointed out by you, I get for 2000 points
(which is actually rather small compared to what we are striving to
have) about 200 interpolations per second via
"surface_neighbor_coordinates_3" whereas for (albeit distorted
projection to) real 2D it is via a pre-calculated triangulation and
"natural_neighbor_coordinates_vertex_2" it is about 250000 (which is
still a tad slow for our purposes, but OK). The problem is that no
suitable (conform) projection exists to map the unit sphere onto any
plane...


Kind regards,
Jörn

--
Jörn Ungermann

Dipl.-Mathematiker
ICG-1, Forschungszentrum Jülich
Tel.: +49 2461 61 1840




-------------------------------------------------------------------
-------------------------------------------------------------------
Forschungszentrum Jülich GmbH
52425 Jülich

Sitz der Gesellschaft: Jülich
Eingetragen im Handelsregister des Amtsgerichts Düren Nr. HR B 3498
Vorsitzende des Aufsichtsrats: MinDir'in Bärbel Brumme-Bothe
Geschäftsführung: Prof. Dr. Achim Bachem (Vorsitzender),
Dr. Ulrich Krafft (stellv. Vorsitzender), Prof. Dr. Harald Bolt,
Dr. Sebastian M. Schmidt
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