I ran on a smaller example with the -info switch set. I preallocated all my matrices (there are two of them, one sequential and one distributed) so that there should be no allocs needed, but I notice it reports: something like: [3] MatAssemblyEnd_SeqAIJ(): Matrix size: 11 X 11; storage space: 10 unneeded,11 used [3] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 0 [3] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 1 [1] MatAssemblyEnd_SeqAIJ(): Matrix size: 10 X 10; storage space: 13 unneeded,10 used [1] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 0 [1] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 1 [2] MatAssemblyEnd_SeqAIJ(): Matrix size: 11 X 11; storage space: 22 unneeded,11 used [2] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 0 [2] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 1 [5] MatAssemblyEnd_SeqAIJ(): Matrix size: 10 X 10; storage space: 9 unneeded,10 used [5] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 0 [5] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 1 [4] MatAssemblyEnd_SeqAIJ(): Matrix size: 9 X 9; storage space: 13 unneeded,9 used [4] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 0 [4] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 1 [0] MatAssemblyEnd_SeqAIJ(): Matrix size: 11 X 11; storage space: 19 unneeded,11 used [0] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 0 [0] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 1 [6] MatAssemblyEnd_SeqAIJ(): Matrix size: 10 X 10; storage space: 17 unneeded,10 used [6] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 0 [6] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 1 [2] MatAssemblyEnd_SeqAIJ(): Matrix size: 11 X 11; storage space: 115 unneeded,31 used [2] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 9 [2] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 5 [5] MatAssemblyEnd_SeqAIJ(): Matrix size: 10 X 10; storage space: 67 unneeded,18 used [5] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 5 [5] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 3 [0] MatAssemblyEnd_SeqAIJ(): Matrix size: 11 X 11; storage space: 88 unneeded,28 used [0] MatAssemblyEnd_SeqAIJ(): Number of mallocs during MatSetValues() is 7 [0] MatAssemblyEnd_SeqAIJ(): Maximum nonzeros in any row is 5
I can't figure why it should allocate anything, b/c I've precomputed the number of entries in each row. > -----Original Message----- > From: owner-petsc-users at mcs.anl.gov > [mailto:owner-petsc-users at mcs.anl.gov] On Behalf Of Barry Smith > Sent: Friday, October 26, 2007 7:54 PM > To: petsc-users at mcs.anl.gov > Subject: RE: Slow assembly > > > > The sorting does not matter. > > Under normal conditions the MatAssembly should take a > fraction of a second. The only cause that we know that slows > it down to the extreme you have is that it is sending a huge > amount of data across processes (the -info option Satish > suggested will tell us if that is true). > > Are you only call MatAssemblyBegin/End() once? You should, > don't call it > multiple times. > > The sorting is not important (in fact it takes advantage of > it automatically and does not need to be set). > > Barry > > > On Fri, 26 Oct 2007, John R. Wicks wrote: > > > I have confirmed that I am calling MatSetValues() for local > rows only > > and am only setting each value exactly once. > > > > Because of how the matrix was partitioned for another non-Petsc > > program, each partition is partitioned (by columns) into 32 blocks > > (corresponding to the row partitions). I enter the data for each > > block one row at a time, i.e., for any one SetValues call, > the entries > > are sorted by increasing column index. Does that mean I can use > > MatrixSetOption(A,MAT_COLUMNS_SORTED). Should that help? > > > > P.S.: I tried it, and it still seems to be taking quite a long time. > > > > > -----Original Message----- > > > From: owner-petsc-users at mcs.anl.gov > > > [mailto:owner-petsc-users at mcs.anl.gov] On Behalf Of Satish Balay > > > Sent: Friday, October 26, 2007 3:04 PM > > > To: petsc-users at mcs.anl.gov > > > Subject: Re: Slow assembly > > > > > > > > > On Fri, 26 Oct 2007, John R. Wicks wrote: > > > > > > > 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? > > > > > > Are you makeing sure that you call MatGetOwnershipRange() - > > > and calling MatSetValues() for mostly local rows only? > > > > > > Also can you confirm that multiple processes [for eg: proc-0 > > > and proc-1 etc..] are not setting the same value [i.e both > > > of them calling MatSetValues(row=0,col=0)] > > > > > > Satish > > > > > > > >
