MatTranspose Question

[Sarah Osentoski]

Hi,

I'll start out by saying I'm a new user to PETSc.  I'm actually using  
SLEPc which is a package for eigenvalue problems and is built on top  
of PETSc and I have a question about the MatTranspose function.

I have a very large, very sparse matrix with dimensions on the order  
of 3 million by 1 million.  I created my matrix using MatCreateMPIAIJ  
and it seems to be evenly distributed across my machines.  I've hit a  
bottleneck when running some code to compute the SVD of the matrix  
and the bottleneck seems to be using the MatTranspose operation on my  
matrix.  This operation runs for a very long time.  I ran a job over  
the weekend and it still seems to be in this function.  (Running for  
on the order of 60 hours at this point.)  It also seems to only being  
using one of the processors available to it.  When MatTranspose runs  
does it go through every element and then send messages between the  
process?  Or for sparse matrices does it only reorder the elements  
that are not zero?  Or is there something else going on that explains  
this behavior?

Thanks,

Sarah Osentoski