Perhaps this is a miscalculation for parallel allocation, meaning you allocate the correct number of values, but do not divide them correctly between the diagonal and offdiagonal parts.
Matt On 10/28/07, John R. Wicks <jwicks at cs.brown.edu> wrote: > 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 > > > > > > > > > > > > > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener
