I am working on computing PageRank for a web scale graph which uses a square matrix which is 1.2x10^8 dimensional with about 10^9 entries. I have partitioned the matrix for 32 processors myself into my own ascii format, and I know the memory allocation, so I:
1) create the matrix with "A = MatCreateMPIAIJ(*n, *n, *N, *N, 0, nnz, 0, onnz)", 2) load the entries by repeatedly calling "MatSetValues(A,1,&row,links,cols,vals,INSERT_VALUES)", and 3) call MatAssemblyBegin/End. Steps 1 and 2 complete in a couple minutes, but step 3 is taking several hours. What is going on? Is there a way to speed up matrix assembly? Thanks, John
