[petsc-users] Parallel matrix assembly questions

[Barry Smith]

On Jan 12, 2011, at 5:31 PM, Hamid M. wrote:

>>   It will affect performance, unless you hope/plan to use iterative solvers there is no good reason to use PETSc for dense matrices with direct solvers. That is another world with a different world of software.
>> 
> 
> Thanks for the helpful response.
> 
> Just from theoretical point of view, are iterative solvers suitable
> for a dense matrix

  It depends on the conditioning of the matrix. For some matrices (for example from some boundary element methods) the system can be solved with a couple dozen GMES iterations which is much much faster than using a direct solver. For other problems GMRES would be slower than a direct solver.

   Barry


> or it doesn't really matter ?
> I know direct solvers would perform faster for problems with multiple
> RHS values and a fixed LHS matrix, but how what are the main factors
> one needs to consider when dealing with dense matrices and various
> solvers.
> 
> Hamid