On 8/17/22 03:10, chong liu wrote:
I modified Step-74 based on the error_estimation part of Step-50. I found it
can work for the attached step-74-mpi, while it cannot work for the attached
step-74-mpi-error. The only difference is the location of the output command
as the attached figure 1 shows. This is weird. The error information states
that one vector is out of bounds as shown in figure 2.
The location of the print message isn't the problem -- it's just that because
you don't end the
std::cout << "...";
call with std::endl, the text is put into a buffer but never printed to
screen. You should run the program in a debugger and check where the erroneous
access comes from. I bet that if the two programs are otherwise the same, they
should both fail.
In addition, there are three points I would like to ask
1. The direct solver cannot work for the modified MPI program. I changed it
to the iterative solver (solver_cg same as Step-40) since I am not
familiar with the MPI direct solver. Could you give me some suggestions on
the direct solver for MPI?
There isn't a good option. There are some parallel direct solvers in both the
PETSc and Trilinos (for which you can probably find information by searching
the mailing list archives), but at the end of the day, if the problem becomes
sufficiently large, even parallel direct solvers cannot compete.
2. Does not ConvergenceTable support the parallel data output? I found that
the first parameter for convergencetable.write_text() is std::out. How can
I modify it to pcout for MPI?
I'm not sure the class supports this, but you can always put a
if (Utilities::MPI::this_mpi_process(...) == 0)
in front of the place where you generate output.
3. I guess the l1_norm() calculation for a vector should be modified. For
example, the code std::sqrt(energy_norm_square_per_cell.l1_norm()) should
be modified to std::sqrt
<https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.dealii.org%2Fcurrent%2Fdoxygen%2Fdeal.II%2Fnamespacestd.html%23aa2def4dc0bd5b6d07af7aff83feba9b2&data=05%7C01%7CWolfgang.Bangerth%40colostate.edu%7C8676b13756db4734d87408da803061ae%7Cafb58802ff7a4bb1ab21367ff2ecfc8b%7C0%7C0%7C637963243499566483%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000%7C%7C%7C&sdata=G7i0Xg9AQIQkzIUAodl745glNO9sRfgnok1piSbkatM%3D&reserved=0>(Utilities::MPI::sum
<https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.dealii.org%2Fcurrent%2Fdoxygen%2Fdeal.II%2FnamespaceUtilities_1_1MPI.html%23ab544a3bf3301a6dd3e705ee352c5551b&data=05%7C01%7CWolfgang.Bangerth%40colostate.edu%7C8676b13756db4734d87408da803061ae%7Cafb58802ff7a4bb1ab21367ff2ecfc8b%7C0%7C0%7C637963243499566483%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000%7C%7C%7C&sdata=dZzc08aCivKuCOOuxnaeEr0ZBSnMB3qRzuVUNDTShvY%3D&reserved=0>(estimated_error_square_per_cell.l1_norm(),
mpi_communicator)).
Yes, something like this.
Best
W.
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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