Hi Karl, sounds great! No reason to hurry :-)
Best regards Andreas > Hi Andreas, > - good news: > I made good progress on introducing a generic context. For code lines > such as > viennacl::vector<T> x = y + z; > the vector x is created in the correct context (i.e. deduced from y, z). > This resolves most of the issues with temporaries. > - bad news: > I haven't found enough time for applying the same scheme to matrices > yet. As the infrastructure is mostly ready, this shouldn't take too long > and be completed during tomorrow. Stay tuned :-) > Best regards, > Karli > On 07/21/2013 09:59 AM, Andreas IHU wrote: >> Hi again, >> >> here's another problem which just occured to me while working with the >> latest developer version from GitHub. >> >> I have a program which has to iteratively solve a number of independent >> equation systems. >> The actual number of systems may vary between 1 and 10. >> Because they are totally independent from each other, we assign each system >> a number of OpenMP threads allowing them to be solved in parallel at the >> same time. >> >> Now I tried to integrate ViennaCL into that scheme and used the >> multithreaded.cpp example as a guide. >> The main difference is that I use OpenMP threads instead of Boost ones. >> >> My approach is to first create as many different OpenCL contexts as equation >> systems do exist and split the existing OpenCL devices over them. >> If just one device exists, its gonna be used by all contexts, which >> shouldn't be a problem. >> Then I call >> >> viennacl::ocl::switch_context() >> >> for every equation system and allocate all the required VCL vectors and >> matrices required just afterwards. >> This makes sure they are assigned and allocated for the context they >> actually belong to. >> This all still takes place in serial mode and doesn't bring me in trouble :-) >> >> The actual problems begin, when the solver routine of our programm is called >> in parallel mode. >> >> 1.) It fills a preallocated STL matrix with the current coefficients and >> updates the RHS vector. >> These are gonna be copied to their VCL counterparts using >> viennacl::copy(stlmat,vclmat); >> What happens exactly during this call is that >> >> viennacl::copy()-> >> viennacl::detail::copy_impl()-> >> gpu_matrix.set()-> >> viennacl::backend::memory_create() (in >> compressed_matrix.hpp at row 519ff) >> >> allocates 3 new buffers which should be created for the context they >> belong to. >> This could be achieved by calling >> viennacl::ocl::switch_context() >> before the copy takes place. >> Unfortunately this isn't an option because I would have to use a OMP >> Critical region to make sure that the parallel calls to switch_context() & >> copy() do not overlap each other leading to race conditions. >> So what I need is an oportunity to specify a context in which the >> copy() takes place without having to change the actual context. >> >> 2.) The same problem happens afterwards when calling the actual >> Preconditioner and solve() routines. >> They too allocate memory for the currently active context. >> >> I built a temporary workaround by putting the whole sequence into a OpenMP >> Critical region which prevents context errors in ViennaCL, >> but makes it impossible to solve the equation systems in parallel. >> >> Any suggestions on that? >> Kind regards >> Andreas Rost >> >> >> >> >> ------------------------------------------------------------------------------ >> See everything from the browser to the database with AppDynamics >> Get end-to-end visibility with application monitoring from AppDynamics >> Isolate bottlenecks and diagnose root cause in seconds. >> Start your free trial of AppDynamics Pro today! >> http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk >> _______________________________________________ >> ViennaCL-devel mailing list >> ViennaCL-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/viennacl-devel >> ------------------------------------------------------------------------------ See everything from the browser to the database with AppDynamics Get end-to-end visibility with application monitoring from AppDynamics Isolate bottlenecks and diagnose root cause in seconds. Start your free trial of AppDynamics Pro today! http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk _______________________________________________ ViennaCL-devel mailing list ViennaCL-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/viennacl-devel
