[mpich-discuss] Sending data many times, packing data or using derived type?

[TAY wee-beng]

Hi,

I am doing computational fluid dynamics and I have a 3D finite volume 
code. I have partitioned the data in the z direction. At times, I need 
to copy some boundary data (1 2d slice) from 1 processor to another. 
They are velocities in u,v and w and contiguous in memory.

Is it recommended to

1. send u,v,w as seperate MPI calls or

2. copy all the u,v,w data into a 1D array and send just once. Then copy 
and update the data or

3. Use derived type and group all these data together? Then copy and 
update the data.

Which is a better choice? Does it depend on the size of the data? I 
think my cluster uses InifiniBand, if I'm not wrong.

-- 
Yours sincerely,

TAY wee-beng