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Reference documentation for deal.II version 9.6.0
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#include <deal.II/base/multithread_info.h>
Public Member Functions | |
MultithreadInfo ()=delete | |
Static Public Member Functions | |
static unsigned int | n_cores () |
static unsigned int | n_threads () |
static std::size_t | memory_consumption () |
static void | set_thread_limit (const unsigned int max_threads=numbers::invalid_unsigned_int) |
static bool | is_running_single_threaded () |
static void | initialize_multithreading () |
static tf::Executor & | get_taskflow_executor () |
Static Private Attributes | |
static unsigned int | n_max_threads = numbers::invalid_unsigned_int |
static std::unique_ptr< tf::Executor > | executor = nullptr |
This class provides information about the system which may be of use in multithreaded programs. At the moment this is just the number of CPUs. If deal.II is compiled with multithreading support, some functions will use multiple threads for their action. Currently the library supports both thread-based and task-based parallelism. Parallel computing with multiple processors accessing shared memory describes the different uses of each. The default number of threads used for task-based parallel methods is selected automatically by the Threading Building Blocks library. See Parallel computing with multiple processors accessing shared memory for more information on this. Thread-based parallel methods need to explicitly create threads and may want to use a number of threads that is related to the number of CPUs in your system. The recommended number of threads can be queried using MultithreadInfo::n_threads(), while the number of cores in the system is returned by MultithreadInfo::n_cores().
Definition at line 57 of file multithread_info.h.
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delete |
Constructor. This constructor is deleted because no instance of this class needs to be constructed (all members are static).
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The number of CPUs in the system.
This internally calls std::thread::hardware_concurrency
but sets the result to 1 if the call returns an error.
Definition at line 40 of file multithread_info.cc.
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Return the number of threads to use. This is initially set to the number of cores the system has (see n_cores()) but can be further restricted by set_thread_limit() and the environment variable DEAL_II_NUM_THREADS.
Definition at line 127 of file multithread_info.cc.
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Return an estimate for the memory consumption, in bytes, of this object. This is not exact (but will usually be close) because calculating the memory usage of trees (e.g., std::map
) is difficult.
Definition at line 144 of file multithread_info.cc.
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Set the maximum number of threads to be used to the minimum of the environment variable DEAL_II_NUM_THREADS and the given argument (or its default value). This affects the initialization of the TBB. If neither is given, the default from TBB is used (based on the number of cores in the system).
This routine is executed automatically with the default argument before your code in main() is running (using a static constructor). It is also executed by Utilities::MPI::MPI_InitFinalize. Use the appropriate argument of the constructor of Utilities::MPI::MPI_InitFinalize if you have an MPI based code.
Definition at line 52 of file multithread_info.cc.
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Return if the TBB is running using a single thread either because of thread affinity or because it is set via a call to set_thread_limit. This is used in the PETScWrappers to avoid using the interface that is not thread-safe.
Definition at line 136 of file multithread_info.cc.
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Make sure the multithreading API is initialized. This normally does not need to be called in usercode.
Definition at line 153 of file multithread_info.cc.
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Return a reference to the global Executor from taskflow.
The Executor is set to use n_threads() worker threads that you can control using set_thread_limit() and the DEAL_II_NUM_THREADS environment variable.
Definition at line 165 of file multithread_info.cc.
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staticprivate |
Variable representing the maximum number of threads.
Definition at line 142 of file multithread_info.h.
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staticprivate |
Store a taskflow Executor that is constructed with N workers (from set_thread_limit).
Definition at line 149 of file multithread_info.h.