Re: [ferret_users] MEMORY/SIZE= changes the result of SAVE

["Ansley C. Manke" <ansley.b.manke@xxxxxxxx>]

Hi,

I suspect this may have to do with Ferret/PyFerret breaking up the computation when computing a number of transformations including @AVE - that's summarized in point 2, here:

https://ferret.pmel.noaa.gov/Ferret/documentation/release_notes/version-7-2-release-notes

This behavior where the results differ does show up for the first time in v7.2. 

Breaking up the computation is done according to the size of the data to be worked on and the available memory setting.  That would explain why changing the size of the computation changes the behavior.  The verbose output of "SET MODE DIAGNOSTIC" lists the operations called scattering and gathering. And a summary is given with "SHOW MEMORY/DIAGNOSTIC".  I'll work with your example and see if I can tell what's going on.

The core analysis code is identical with Ferret and Pyferret, so we wouldn't expect differences there.

-Ansley

On 12/17/2019 4:52 AM, Ryo Furue wrote:

Hi, again,

Just one more experiment.

On Mon, Dec 16, 2019 at 1:31 PM Ryo Furue <furue@xxxxxxxxxx> wrote:

Unfortunately, I've just reproduced exactly the same problem on Ferret 7.5.0 on Linux.  So far, we haven't got Pyferret on our Linux server.

So, the same problem is reproduced with PyFerret 7.5 on the same Linux machine:

On PyFerret 7.5 on my Mac, exactly the same problem occurs with the same dataset.  So, it's more likely that other people can reproduce the problem.

Regards,

Ryo

 

The presence or absence of a SET MEMORY command changes the result of SAVE without any diagnostics.

I'll try to further reduce my data file.

Regards,

Ryo

-----------

  NOAA/PMEL TMAP
  PyFerret v7.5 (optimized)
  Linux 4.15.0-1061-azure - 11/14/19
  16-Dec-19 13:21

====================

  NOAA/PMEL TMAP
  FERRET v7.5 (optimized)
  Linux 2.6.32-754.11.1.el6.x86_64 64-bit - 04/25/19
  16-Dec-19 00:02

 

!=== my script to reproduce the bug ===

! Delete the SET MEMORY command and the two output variables become identical.
!

set data tmp-usss0500m-L600.nc ! Contains var "usss" .

set memory/size=300 ! <- Delete this line
let u = usss[d=1]
save/clobber/file=tmp-u.nc  u[m=1:10@AVE]
save/clobber/file=tmp-usss.nc  usss[m=1:10@AVE]

!--- plot to see if they are identical ---
cancel var/all
cancel data/all
set data tmp-u.nc
set data tmp-usss.nc
plot/x=101W/y=4S:4N u[d=1], usss[d=2]