pnetcdf question

[William Gropp]

At 01:59 PM 3/18/2004, Foucar, James G wrote:
>Hi Rob, thanks for the reply. i was thinking along the same lines. the
>reason i am hestitant to do the:
>
>array 1: 1a 1b 1c 2a 3a 3b 3c 3d 4a 4b 4c
>array 2: 3 1 4 3
>
>implementation is because it will require communication between the
>processors to figure out what offset they should be writing to. so, right
>now i am leaning towards separate variables per process. this will require
>me to enter "independent data mode", correct? will this cause me to take a
>performance hit?

If all you need to do is to compute the offset, the  MPI_Scan routine will 
do this fairly efficiently (if you have a good implementation).  If you 
have an MPI-2 implementation, MPI_Exscan is a closer match to what you 
need.  The communication cost should be small relative to the I/O cost.

Bill