Re: regridding and memory

[Ansley Manke <ansley@xxxxxxxxxxxxx>]

Hi Benyang,
It turns out that this is due to a bug in @AVE regridding, where in some
cases the wrong range of indices is used in computing the average for
regridding.  The bug is in versions 5.22  - 5.40 of Ferret.  We have a fix
for it, which will be in the version 5.41 release.   Here's a related report
and reply.
http://ferret.wrc.noaa.gov/Ferret/Mail_Archives/fu_2002/msg00132.html

The bug is is only with @AVE; other regridding transforms will give you
correct results.

Ansley Manke

Benyang Tang wrote:

> I don't know how to make sense of the following Ferret section.
>
> I did
> list topo1[x=100,y=100]
> three times. Every time the value changed; no calculation was performed on the variable.
>
> The first list was 32.39, which was incorrect.
> The second list was 4715, after I listed the variable topo1 in a range.
> The third list was back to 32.39, after memory resizing.
>
> Any suggestions? Thanks.
>
> Benyang Tang
>
> ========================================
> $ ferret -gif
>         NOAA/PMEL TMAP
>         FERRET v5.40
>         Linux 2.4.3-12smp - 02/19/02
>         28-May-02 17:07
> yes? define axis/y=1:224:1/unit=meters oldY
> yes? define axis/x=1:360:1/unit=meters oldX
> yes? define grid/y=oldY/x=oldX oldG
> yes?
> yes? FILE/VAR=topo/GRID=oldG/FORMAT=stream/type=r4/swap  "topog.dat"
> yes?
> yes? define axis/y=1:224:2/unit=meters newY
> yes? define axis/x=1:360:2/unit=meters newX
> yes? define grid/y=newY/x=newX newG
> yes?
> yes? define var topo1=topo[g=newG@ave]
> yes?
> yes? list topo1[x=100,y=100]
>              VARIABLE : TOPO[G=NEWG@AVE]
>              FILENAME : topog.dat
>              X (METERS): 99
>              Y (METERS): 99
>           32.39
> yes?
> yes? list topo1[x=98:102,y=98:102]
>              VARIABLE : TOPO[G=NEWG@AVE]
>              FILENAME : topog.dat
>              SUBSET   : 2 by 2 points (X (METERS)-Y (METERS))
>                99     101
>                50     51
>  99    / 50:  4715.  2782.
>  101   / 51:    24.     6.
> yes?
> yes? list topo1[x=100,y=100]
>              VARIABLE : TOPO[G=NEWG@AVE]
>              FILENAME : topog.dat
>              X (METERS): 99
>              Y (METERS): 99
>           4715.
> yes? set memory/size=100
>  Cached data cleared from memory
> yes?
> yes? list topo1[x=100,y=100]
>              VARIABLE : TOPO[G=NEWG@AVE]
>              FILENAME : topog.dat
>              X (METERS): 99
>              Y (METERS): 99
>           32.39

--
Ansley Manke  Pacific Marine Environmental Laboratory  Seattle WA  (206)526-6246