Thank you for the reply.
Your understanding of my problem is exactly correct. Even though the data I
am writing is small, I have tried complicated operations inside, but still
there is no improvement.
I agree this is low level code. I will try your suggestion about the map
between user pointer and the data. Anyway, my ultimate goal is to write the
code running on cluster. So, I need to learn further about MPI, and maybe I
will post new questions then.
Thank you again.
Best,
Chenchen
在 2016年5月20日星期五 UTC-4上午5:33:33，mac写道：
>
> Hi Chenchen
>
> Just so that I understand: are you currently solving the problem using the
> same approach (i.e. distributing the cells, solving the microscopic problem
> at each quadrature point of the cells). You have the solution and now you
> want to write it into a global history vector?
>
> When you say it can not save any time - what do you mean? You have a very
> small number of processors (4 I think) and the data you are writing looks
> small. Would you expect to see a speed up?
>
> There might be better ways to write multiple chunks of data into a vector
> than what you have suggested (your approach seems a bit low level). Perhaps
> someone can suggest an alternative strategy? A map between the cell user
> pointer and the data you want to store might be a better idea.
>
>
> A
>
>
> Let's simplify the problem as:
> First, we have a 1-D macro mesh, and at each element (interval) we have 2
> quadrature points. On each quadrature point, we generate a new Vector,
> i.e., solution_x. Then, I want to remember this Vector by writing it into
> local_quadrature_point_history().
>
> I have written the following code, expecting that we can divide the entire
> elements into 4 sub_ranges, and write new Vector to
> local_quadrature_point_history() in parallel. But it turns out that it
> cannot save any computational time. Can anyone give me any suggestions?
> Thank you!
>
>
> void Step3::Write_problem_on_cell_range (DoFHandler<1>::cell_iterator
> &range_begin,
>
>
> DoFHandler<1>::cell_iterator &range_end)
>
> {
>
> const unsigned int n_q_points = quadrature_formula_MACRO.size();
>
> static Threads::Mutex mutex;
>
> Threads::Mutex::ScopedLock lock (mutex);
>
>
> DoFHandler<1>::cell_iterator cell_MACRO = range_begin, endc_MACRO =
> range_end;
>
> for (; cell_MACRO!=endc_MACRO; ++cell_MACRO)
>
> {
>
> // build history
>
> PointHistory<1> *local_quadrature_points_history_MACRO
>
> = reinterpret_cast<PointHistory<1> *>(cell_MACRO->user_pointer());
>
>
> // BEGIN RVE problem
>
> for (unsigned int q_index = 0; q_index<n_q_points; ++q_index)
>
> {
>
> solution_x_RVE[0] = 1; solution_x_RVE[1] = 2;
>
> // Write
>
>
> local_quadrature_points_history_MACRO[q_index].solution_x_RVE_h =
> solution_x_RVE;
>
> }
>
> }
>
> }
>
>
> void Step3::Write_problem ()
>
> {
>
> static unsigned int n_virtual_cores = MultithreadInfo::n_threads();
>
> Threads::ThreadGroup<void> threads;
>
>
> std::vector<std::pair<DoFHandler<1>::cell_iterator,DoFHandler<1>::cell_iterator>
>
> >
>
> sub_ranges = Threads::split_range <DoFHandler<1
> >::cell_iterator>(dof_handler_MACRO.begin_active(),
>
>
> dof_handler_MACRO.end(),
>
>
> n_virtual_cores);
>
>
> for (unsigned int t=0; t<n_virtual_cores; ++t)
>
> threads += Threads::new_thread
> (&Step3::Write_problem_on_cell_range, *this,
>
>
> sub_ranges[t].first, sub_ranges[t].second);
>
> threads.join_all();
>
> }
>
>
>
>
>
> Best,
>
> Chenchen
>
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