[MITgcm-support] bug in exch2?

[Martin Losch]

Hi there,

there seems to be an initialisation issue in one/some of the exch2  
routines. On our beloved (God, I hate this machine) SX8, the high-res- 
cube stops with errors like this:
>    * 253 Invalid operation PROG=exch2_send_rl2 ELN=1627(40049c9d8)
>                  Called from read_pickup ELN=2022(40083c6a8)
>                  Called from ini_fields ELN=1703(4007d9d18)
>                  Called from initialise_varia ELN=2018(4008154cc)
> ****  99 Execution suspended PROG=exch2_send_rl2 ELN=1627(40049c9d8)
>                  Called from exch2_rl2_cube ELN=1966(40048c594)
>                  Called from exch2_uv_3d_rl ELN=1603(4004a4a74)
>                  Called from exch_uv_3d_rl ELN=1826(4006f8478)
>                  Called from read_pickup ELN=2022(40083c6a8)
so at the first uv exchange. A closer look confirms that array1 and  
array2 in exch2_send_rl2 have nans on them in the overlap. This  
problem goes away, when I make the compile initialise everything to  
zero by default. (I also learned that apparently not the entire  
overlap is exchanged in exch2_rl2_cube, but only olx-1,oly-1 points,  
at least for cubed exchanges; that would explain, why two exchanges  
are necessary, wouldn't it?)

Martin