[MITgcm-support] Segmentation fault trying to capture location in ptracers array.

[Jonathan Lauderdale]

Hello,

I am trying to add a few passive/preformed tracers to the end of the pTracers array. In my code (gchem_forcing_sep.F to be precise), I cycle through the extra tracers in a “do” loop and use PTRACERS_names to decide how to reset the surface values (e.g. preformed phosphate, ppre, is reset to surface po4 values; cpre to surface dic values). This works great. 

For a few calculations later, I want to capture the order of these extra tracers (if they exist) and pass them as arguments to a subroutine, similar to how dic_biotic_forcing is done. Sounds simple...My minimal working example loop is as follows:

>        INTEGER nTrac
>        INTEGER itrc_apre,itrc_ppre,itrc_pco2 
>        CHARACTER*(MAX_LEN_FNAM) fldName
> 
> [….reset preformed surface tracer concentration…]
> 
>        DO nTrac=1,PTRACERS_num,1
>          fldName=PTRACERS_names(nTrac)
>          IF ( fldName(1:4) .EQ. 'apre' ) THEN
>             itrc_apre=nTrac         
>          ELSEIF ( fldName(1:4) .EQ. 'ppre' ) THEN
>             itrc_ppre=nTrac
>          ELSEIF ( fldName(1:7) .EQ. 'atmpco2' ) THEN
>             itrc_pco2=nTrac
>          ENDIF         
>        ENDDO

I keep getting the following error and I am having a nightmare trying to figure out what is wrong:

> Program received signal SIGSEGV: Segmentation fault - invalid memory reference.
> 
> Backtrace for this error:
> #0  0x160a7fa52
> #1  0x160a8021e
> #2  0x7fff92dc9f19
> #3  0x10f784c68
> #4  0x10f739973
> #5  0x10f74ae31
> #6  0x10f972c95
> #7  0x10f9b2818
> #8  0x10f9b2910
> #9  0x10f92a61d
> #10  0x10f9bbdb8
> Segmentation fault: 11


I did think it might have something to do with interfering with the do-loop index, nTrac, but I tried it with a dumb counter with no success:

>        INTEGER nTrac,tmp1,tmp2,tmp3
>        INTEGER itrc_apre,itrc_ppre,itrc_pco2 
>        CHARACTER*(MAX_LEN_FNAM) fldName
> 
> [….reset preformed surface tracer concentration…]

>        tmp1=0
>        DO nTrac=1,PTRACERS_numInUse
>          fldName=PTRACERS_names(nTrac)
>          tmp1=tmp1+1
>          IF ( fldName(1:4) .EQ. 'apre' ) THEN
>             itrc_apre=tmp1 
>          ENDIF         
>        ENDDO
>  
>        tmp2=0
>        DO nTrac=1,PTRACERS_numInUse
>          fldName=PTRACERS_names(nTrac)
>          tmp2=tmp2+1
>          IF ( fldName(1:4) .EQ. 'ppre' ) THEN
>             itrc_ppre=tmp2
>          ENDIF         
>        ENDDO
> 
>        tmp3=0
>        DO nTrac=1,PTRACERS_numInUse
>          fldName=PTRACERS_names(nTrac)
>          tmp3=tmp3+1
>          IF ( fldName(1:7) .EQ. 'atmpco2' ) THEN
>             itrc_pco2=tmp3
>          ENDIF         
>        ENDDO

I guess I will just have to hard code these locations in if not, but it would be nice to get this working! Thanks in advance!

Jon

___________________________________________________________________________
Dr. Jonathan M. Lauderdale
Postdoctoral Research Associate
Department of Earth, Atmosphere and Planetary Sciences 
Massachusetts Institute of Technology 
77 Massachusetts Avenue 
Cambridge, MA 02139, USA 
Office: +1 617 324 3401 
Cell   : +1 617 304 5661
Email: <mailto:jml1 at mit.edu <mailto:jml1 at mit.edu>>
Web: <http://eaps-www.mit.edu/paoc/people/jonathan-lauderdale <http://eaps-www.mit.edu/paoc/people/jonathan-lauderdale>>
Association of Polar Early Career Scientists <http://www.apecs.is/ <http://www.apecs.is/>>
___________________________________________________________________________

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