I think the reason is that step-17 uses an inefficient constructor for
the system matrix:
system_matrix.reinit (mpi_communicator,
dof_handler.n_dofs(),
dof_handler.n_dofs(),
n_local_dofs,
n_local_dofs,
dof_handler.max_couplings_between_dofs());
This will lead to very slow setup and large memory requirements. You
can try something closer to what is used in step-40 (using
DynamicSparsityPattern).
On Fri, Jul 29, 2016 at 3:41 PM, Pete Griffin <[email protected]> wrote:
> I did another plot (see attached) of Memory usage vs. #DOF with step-18.
> This is, as the other two, a 3d elasticity problem. The results in terms of
> memory usage were in line with step-8 and contrasted step-17. I will try to
> understand step-18 well enough to transfer the MPI/PETSc stuff to step-17
> with the goal of getting memory usage of step-17 down to expected. Whether
> the changes it will work on multiprocessor system I will have no way of
> knowing since I run only on a single processor.
>
> Pete Griffin
>
>
> On Monday, July 25, 2016 at 1:59:53 PM UTC-4, Pete Griffin wrote:
>>
>> I found that running step-8 and step-17 on a single processor Intel® Core™
>> i7-3630QM CPU @ 2.40GHz × 8 used substantially more Peak resident memory (>
>> 5x) than I thought it would. This surprised me since I thought from reading
>> step-17 that the memory increase was on the order of the solution vector
>> which should have been << 2x greater. I verified some of the larger memory
>> usage numbers using top.
>>
>> Is my assumption correct that 5x Peak resident memory is more than it
>> should be?
>>
>> The results of other simulations with a beam with body-force load and with
>> traction loads with and without HP and with and without MPI/PETSc all show
>> the same results and they agree with beam theory.
>>
>> The output of the modified step-8.cc and step-17.cc are attached along
>> with a plot of peak virtual memory and peak resident memory
>> vs. DOF. The changes between the original distributed step-8 and step-17,
>> with comments and extra newlines excluded (modified file >), are as below:
>>
>> Thanks beforehand
>>
>> Pete Griffin
>>
>>
>> ======================================================================================
>> diff ~/Documents/Zipstore2/dealii-8.4.1-PETSc/examples/step-8/step-8.cc
>> step-8.cc
>> 56c47,48
>> < // This again is C++:
>> ---
>> > #include <deal.II/base/utilities.h>
>>
>> 767a394,402
>> >
>> > Utilities::System::MemoryStats stats;
>> > Utilities::System::get_memory_stats(stats);
>> > std::stringstream Str;
>> >
>> > Str.str("");
>> > Str << " Peak virtual memory: " << stats.VmSize/1024 << " MB,
>> > Peak resident memory: "
>> > << stats.VmRSS/1024 << " MB" << std::endl;
>> > std::cout << Str.str();
>>
>> 781c411
>> < Step8::ElasticProblem<2> elastic_problem_2d;
>> ---
>> > Step8::ElasticProblem<3> elastic_problem_2d;
>>
>>
>> ======================================================================================
>> diff ~/Documents/Zipstore2/dealii-8.4.1-PETSc/examples/step-17/step-17.cc
>> ../step-17/step-17.cc
>> 84a50
>> > #include <deal.II/base/utilities.h>
>> 1015c355
>> < for (unsigned int cycle=0; cycle<10; ++cycle)
>> ---
>> > for (unsigned int cycle=0; cycle<8; ++cycle)
>> 1018d357
>> <
>> 1022c361
>> < triangulation.refine_global (3);
>> ---
>> > triangulation.refine_global (2);
>> 1049a383,391
>> >
>> > Utilities::System::MemoryStats stats;
>> > Utilities::System::get_memory_stats(stats);
>> > std::stringstream Str;
>> >
>> > Str.str("");
>> > Str << " Peak virtual memory: " << stats.VmSize/1024 << " MB,
>> > Peak resident memory: "
>> > << stats.VmRSS/1024 << " MB" << std::endl;
>> > std::cout << Str.str();
>> 1073,1074c403
>> <
>> < ElasticProblem<2> elastic_problem;
>> ---
>> > ElasticProblem<3> elastic_problem;
>>
>>
>> =============================================================================================
>>
> --
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--
Timo Heister
http://www.math.clemson.edu/~heister/
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