Re: triple2grid

Dear Imran,

Thanks so much for providing a sample code and data file. I'll take a
look and see if I can reproduce the problem.

The default value of distmx is supposed to be 1e20. Either this is
not getting set correctly, or, as you pointed out, this value may not
be a good default to use.

We'll keep you posted.

--Mary

On Apr 13, 2010, at 6:43 AM, IMRAN NADEEM wrote:

> Dear Ashley, Mary, Dennis and Rick,
>
> Today I was playing with triple2grid function and trying to
> understand the segmentation fault problem recently reported by
> Ashley. Infact I was facing the similar problem. I used the input
> data and ncl script sent by Ashley last month.The objective is to
> use nearest neighbor approach for regridding temperature from model
> native grid (25km) to regular grid (0.25 deg). Here is how I
> overcome the problem:
>
> First, I run the attached script on three different machines. On
> two machines, I got the segmentation fault but on third machine,
> the script runs fine and I got the output file but the output
> field was wrong. See the attached image output_default.gif. I don't
> understand why this is so? On all three machines NCL was installed
> from pre-compiled binaries and have the same version 5.1.1.
>
> Next instead of using default option, I set opt = True, opt@distmx
> = 50 and every thing was perfect. On all three
> machines, I got the same results. See the attached image
> output_distmx_50km.gif
>
> So, I conclude that default value of distmx is responsible for
> segmentation problem. I suggest to mention in the documentation of
> triple2grid to use reasonable values for distmx incase input data
> is gridded.
>
> I hope it will help others.
>
> Best Regards
> PhD Student & Research Assistant
> Imran Nadeem
> BOKU, Vienna
>
>
>
> On Tue, Mar 9, 2010 at 7:41 PM, Rick Brownrigg <brownrig@ucar.edu>
> wrote:
> > Ashley,
> > I'm not sure what to suggest regarding a workaround for
> area_hi2lores, short
> > of iteratively calling the function on smaller pieces of your
> input grids
> > (if that even makes numerical sense). And unfortunately, the 2GB
> issue
> > holds for the 64bit versions as well. The NCL team is working to
> lift this
> > constraint.
> > Rick
> >
> > On Mar 9, 2010, at 2:23 AM, Ashley Watson wrote:
> >
> > Hi again,
> > Thanks Rick, today I encountered the similar problem using
> > area_hi2lores. Is there a workaround to overcome this
> > memory limitation(segmentation fault). Also the NCL's 2GB data
> limit is for
> > 32bit version or its the same on 64bit version. I mean, if I
> install NCL on
> > 64bit machine with 32GB of memory can I oversome this problem.
> > Ashley
> >
> > On Wed, Mar 3, 2010 at 5:56 PM, Rick Brownrigg
> <brownrig@ucar.edu> wrote:
> >>
> >> Hi Ashley,
> >> It could be that you are running up against NCL's 2GB data limit
> (?). The
> >> docs for triple2grid state that the return result will be:
> >> "The return array will be K x N x M, where K represents the
> leftmost
> >> dimensions of data. It will be of type double if any of the
> input is double,
> >> and float otherwise."
> >> After ndtooned(orog), the left (and right!) dimension is 38400,
> rlon is
> >> 181, rlat is 133, to yield:
> >> 38400x181x133xsizeof(float) = 3.69GB
> >> In any case, something other than a SEGV would be preferable.
> >> Not sure that helps...
> >> Rick
> >> On Mar 3, 2010, at 7:39 AM, Ashley Watson wrote:
> >>
> >> Dear All,
> >>
> >> I am trying to use nearest neighbor approach for regridding
> temperature
> >> from model native grid to regular grid. As rcm2rgrid doesn't
> employ nearest
> >> neighbor
> >> method, I tried to use triple2grid but I am stuck with
> segmentation
> >> fault. My script and sample input data is attached. The attached
> script
> >> works fine
> >> for rcm2rgrid but not for triple2grid. Why triple2grid is not
> working?
> >>
> >> Thanks in advance
> >> Ashley
> >>
> >>
> >>
> >>
> <Test_input.nc><Test_triple2grid.ncl>_________________________________
> ______________
> >> ncl-talk mailing list
> >> List instructions, subscriber options, unsubscribe:
> >> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
> >>
> >
> > _______________________________________________
> > ncl-talk mailing list
> > List instructions, subscriber options, unsubscribe:
> > http://mailman.ucar.edu/mailman/listinfo/ncl-talk
> >
> >
> > _______________________________________________
> > ncl-talk mailing list
> > List instructions, subscriber options, unsubscribe:
> > http://mailman.ucar.edu/mailman/listinfo/ncl-talk
> >
> >
>
> <Test_input.nc><Test_triple2grid_modified.ncl><InputData.gif><output_d
> efault.gif><output_distmx_50km.gif>
> _______________________________________________
> ncl-talk mailing list
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk

_______________________________________________
ncl-talk mailing list
List instructions, subscriber options, unsubscribe:
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Tue Apr 13 08:07:16 2010