what does P and Q represent?

[wojiushishen]

No description provided.

[Yidasvc]

In process grid load balance strategy, P * Q == NP(number of processes). All processes are shaped into P rows and Q columns. Sparse blocks of distributed matrix are placed on P*Q processes.
For example, there is a matrix, N==6(order is 6), set NB=2(order of each non-zero block is 2), then block_length==3 (ceil(N/NB)). block-level sparse pattern is shown below:

  0 1 2
0 * * 
1 * * *
2   * *

Numbering each non-zero blocks row by row, then numbers of non-zero blocks are 0~6.
If P==Q==2, numbering processes row by row from 0 to 3, then:
block 0,6 are placed on process 0;
block 1,5 are placed on process 1;
block 2,4 are placed on process 2;
block 3 is placed on process 3.