About neighboring proc for comm tiled?

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1

Dear Dr. Axel

As I read the comm.h, there is an array which store the 6 neighbors of a processor: procneigh[3][2]. For “comm_style tiled”, the neighboring processors is larger than 6 as can be shown in the figure from the “fix balance” command. I am wondering is there another array to store the neighboring processor for comm_style tiled. Thanks very much!

Hao

2

Dear Dr. Axel

As I read the original paper from Steve, the communication for uniform grid is along the three directions, up-down, north-south and east-west. I am wondering how you do the communication for comm_tiled as in the north direction there can be several processors to communicate. Thanks very much!

Hao

3

Comm brick does the 6-neighbor communication. Comm tiled does it differently.

Obviously it’s more complicated. See these sections in comm_tiled.h which

store the needed info:

// forward/reverse comm info, proc lists include self
// exchange comm info, proc lists do not include self

Steve

4

Thanks very much, Steve. I am wondering if there is some paper like the LAMMPS paper which describe how the communication works for “comm_style tiled”. Thanks. Hao

5

You probably want to read about the RCB (Recursive Coordinate Bisection) Algorithm. A small explanation with some links here: http://www.cs.sandia.gov/zoltan/dev_html/dev_rcb.html

6

Thanks, Diaz, Adrian. I think that RCB is the algorithm for balancing the load of each processor. Do you know how they communicate with each other after the balance work is done? Hao

7

Thanks, Diaz, Adrian. I think that RCB is the algorithm for balancing the
load of each processor. Do you know how they communicate with each other
after the balance work is done? Hao

​as steve already pointed out, you have to read through the comm_tiled.cpp
file to see how this is done.​ if you want to know things at this level of
detail, there is no way around reading the source code and the comments and
tracking what is happening with a piece of paper and a pen.

​axel.​

8

Thanks, Axel.