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#1214 (Division by zero in lim_itd_me_ridgeprep (LIM3)) – NEMO

Opened 9 years ago

Closed 8 years ago

Last modified 8 months ago

#1214 closed Bug (fixed)

Division by zero in lim_itd_me_ridgeprep (LIM3)

Reported by: ufla Owned by: vancop
Priority: normal Milestone:
Component: LIM3 Version: v3.6
Severity: Keywords: LIM* v3.6


When running r4346 of dev_MERGE_2013 I get division by zero in line 682 of LIM_SRC_3/limitd_me.F90 when astar is used:

astari = 1.0/astar

This variable should be initialised from namelist namiceitdme in subroutine lim_itd_me_init, however, the above line is reached via the call tree:

sbc --> sbc_ice_lim
      --> lim_dyn
        --> lim_rhg
          --> lim_itd_me_icestrength
            --> lim_itd_me_ridgeprep

So, in that case, lim_itd_me_init is not called before before the use of astar (and other variables?).

Commit History (1)


moved the call to lim_itd_me_init to initialize variables at right moment, see ticket #1214 and #1308

Attachments (1)

limitd_me.F90.patch (988 bytes) - added by ufla 9 years ago.
Patch that moves the initialisation of the limitd_me. (Not suggested as permanent fix)

Download all attachments as: .zip

Change History (12)

comment:1 Changed 9 years ago by ufla

I can add that in sbc_ice_lim, lines 337--342, lim_dyn is called first (and triggers the error), whereas lim_itd_me (which in turn calls lim_itd_me_init) is called afterwards, which is too late.

comment:2 Changed 9 years ago by clem

I do not see your point here. Maybe I'm wrong but to me, astar is initialized at the very beginning of the module limitd_me.F90 (via the call to lim_itd_me_init). Therefore astari, which is used later on in the same module (in lim_itd_me_ridgeprep) should also be defined right?

comment:3 Changed 9 years ago by ufla

Correct, astar is initialised in lim_itd_me_init, which is called from lim_itd_me. However, the code in sbcice_lim.F90 (lines 337..341) looks like this:

337    CALL lim_dyn( kt )
341    CALL lim_itd_me

So before lim_itd_me is called (and initialises astar via lim_itd_me_init), there is a call to lim_dyn. This leads to a call to lim_itd_me_ridgeprep, which uses astar. This means that the call to lim_dyn bypasses lim_itd_me and, hence, lim_itd_me_init.

Put in another way: There are two places that call lim_itd_me_ridgeprep, one is lim_itd_me (which makes sure all is initialised) and the other is lim_itd_me_icestrength (which bypasses initialisation).

I run into the problem when I tested the code with floating point exceptions enabled. It says division by zero and using a debugger I found the astar being zero when used in lim_itd_me_ridgeprep.

comment:4 Changed 9 years ago by ufla

Just as a test, i moved the line that initialises the limitd_me module:

IF( numit == nstart  ) CALL lim_itd_me_init ! Initialization (first time-step only)

from the lim_itd_me subroutine to lim_itd_me_icestrength and that makes to code work. Of course, I have no idea about side-effects, so I'm not assuming that this is a good fix. See attached patch.

Changed 9 years ago by ufla

Patch that moves the initialisation of the limitd_me. (Not suggested as permanent fix)

comment:5 Changed 9 years ago by clevy

  • Owner changed from NEMO team to vancop

comment:6 Changed 8 years ago by flavoni

fix in revision 4831 of trunk:

moved call to initialization of lim_itd_me_init in iceini.F90

(this solution works also for ticket #1308)


comment:7 Changed 8 years ago by flavoni

  • Resolution set to fixed
  • Status changed from new to closed

comment:8 Changed 5 years ago by nemo

  • Keywords LIM* added

comment:9 Changed 5 years ago by nemo

  • Keywords release-3.6* added

comment:10 Changed 5 years ago by nemo

  • Keywords release-3.6* removed

comment:11 Changed 8 months ago by nemo

  • Keywords v3.6 added
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