On 10/03/2017 01:04 AM, 'Maxi Miller' via deal.II User Group wrote:
I have a system of coupled heat equations, written for MPI using
| LinearAlgebraTrilinos::MPI::SparseMatrixsystem_matrix; |
as the sparse system matrix. Now for certain values the program runs fine,
but for other values (which I am interested in) the RAM consumption goes up
rapidly after several steps in time and refinement.
Valgrind tells me that the biggest reason for that is the system matrix.
This makes the program unusable workstations with 32 GByte RAM. Is that
something I could expect, or is that a bug in my program?
It's likely a bug of some sort, unless you are solving problems with LOTS of
unknowns. A general rule is that you need maybe 1500 or 2000 bytes per
unknown, so you should be able to solve problems with several million unknowns
with 32 GB. How large are the problems you have?
I am solving the equations with the method shown in step-15 and step-33,
i.e. I iterate over an inner loop for every time step until I am below a
certain l2-value, and then go to the next time point.
One possible approach I could think of is to set the threshold higher, but
that would only delay the problem. Another approach would be to check if
the l2-value did not change over the last five internal loops,
and then continue anyway, but that would again increase the error. Is there
a better way?
That doesn't make any sense to me. The only thing that should increase the
memory consumption should be mesh refinement. The number of iterations should
have no effect. If it does, then you have a memory leak somewhere.
Best
W.
--
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Wolfgang Bangerth email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/
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