Hi Hazen:
On 2015-05-13 11:46-0400 Hazen Babcock wrote:
>
> Hello Alan, Arjen,
>
> As I mentioned before, the FPE's in x25c, x30c and x33c are all coming from
> the notcrossed() function in plfill.c. Hopefully you can provide some insight
> as the authors. Basically the problem arises in a situation where the two
> lines do not cross, but are not parallel.
> In this situation this function
> still calculates the x,y intersection. However, depending on the position and
> orientation of the two lines this intersection can be way outside the range
> of values that can be represented using (4 byte) integers. Do you recall if
> functions that call this function expect to receive a valid intersection
> point in this case? Or is it ok to just return zero?
Hi Hazen:
I have reviewed plfill.c, and the returned intersection from
notcrossed is only used when status is zero. So I have (commit ID =
b916d4b) considerably simplified noncrossed to do the PLINT
transformation of the intersection and return those values _only_ when
status = 0.
This change solved all fpe problem for examples 25 and 30, but there
are remaining fpe issues for fortran examples 21 and 33. The logic in
noncrossed is pretty bullet-proof now so my prediction is those
remaining fpe issues are completely independent of notcrossed or else
there is a non-initialized variable somewhere in fortran examples 21
and 33. But I look forward to your definitive conclusion concerning
those remaining fpe issues.
Alan
__________________________
Alan W. Irwin
Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).
Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
__________________________
Linux-powered Science
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