Ah, I see and that makes perfect sense. I'v been slightly exposed to TaskFlow and it's interesting y'all are planning on using it. I will look more into this project!
Thank you, Zachary On Monday, November 30, 2020 at 7:18:05 PM UTC-6 Wolfgang Bangerth wrote: > On 11/30/20 6:05 PM, Zachary Streeter wrote: > > > > I mainly would like a good old ```#pragma omp for``` to parallelize > > for-loops. Should I use a "workstream" for this? Can someone point me > in the > > right direction within deal.II to look for these capabilities? I > imagine all > > the classics like scan and reduction, etc., must be in this project. > > The problem with #pragma omp for is that, almost universally, it only > helps > you parallelize the innermost loops. But these loops are also almost > universally short and breaking them up into 16 or 64 threads leads to so > many > synchronization points that it's not worth it on machines with substantial > core counts. > > What you need to do instead is to parallelize the outermost loops -- say, > the > loop over all cells when assembling a linear system. Here, you do orders > of > magnitude more work, and consequently have orders of magnitude fewer > synchronization points. But #pragma omp for can't express the complexities > of > these kinds of loops: The counter over the elements may actually be an > iteration of class type (not supported by OpenMP), the variables that are > thread-local or shared are not just simple C-style objects but classes > themselves with complex semantics, etc. As a consequence, we've always > tried > to avoid using OpenMP for parallelization -- the only efficient way to do > it > is using systems such as WorkFlow or task-based parallelism. > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: [email protected] > www: http://www.math.colostate.edu/~bangerth/ > > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/3f68f4b0-4738-4305-a3eb-ae8164bb5a03n%40googlegroups.com.
