Visible to Intel only — GUID: GUID-567F8768-04A6-4C8C-8869-385FB416C8D8
Package Contents
Parallelizing Simple Loops
Parallelizing Complex Loops
Parallelizing Data Flow and Dependence Graphs
Work Isolation
Exceptions and Cancellation
Floating-point Settings
Containers
Mutual Exclusion
Timing
Memory Allocation
The Task Scheduler
Design Patterns
Migrating from Threading Building Blocks (TBB)
Constrained APIs
Appendix A Costs of Time Slicing
Appendix B Mixing With Other Threading Packages
References
parallel_for_each Body semantics and requirements
parallel_sort ranges interface extension
TBB_malloc_replacement_log Function
Type-specified message keys for join_node
Scalable Memory Pools
Helper Functions for Expressing Graphs
concurrent_lru_cache
task_group extensions
The customizing mutex type for concurrent_hash_map
Visible to Intel only — GUID: GUID-567F8768-04A6-4C8C-8869-385FB416C8D8
Timing
When measuring the performance of parallel programs, it is usually wall clock time, not CPU time, that matters. The reason is that better parallelization typically increases aggregate CPU time by employing more CPUs. The goal of parallelizing a program is usually to make it run faster in real time.
The class tick_count in Intel® oneAPI Threading Building Blocks (oneTBB) provides a simple interface for measuring wall clock time. A tick_count value obtained from the static method tick_count::now() represents the current absolute time. Subtracting two tick_count values yields a relative time in tick_count::interval_t, which you can convert to seconds, as in the following example:
tick_count t0 = tick_count::now();
... do some work ...
tick_count t1 = tick_count::now();
printf("work took %g seconds\n",(t1-t0).seconds());
Unlike some timing interfaces, tick_count is guaranteed to be safe to use across threads. It is valid to subtract tick_count values that were created by different threads. A tick_count difference can be converted to seconds.
The resolution of tick_count corresponds to the highest resolution timing service on the platform that is valid across threads in the same process. Since the CPU timer registers are not valid across threads on some platforms, this means that the resolution of tick_count can not be guaranteed to be consistent across platforms.
NOTE:
On Linux* OS, you may need to add -lrt to the linker command when you use oneapi::tbb::tick_count class. For more information, see http://fedoraproject.org/wiki/Features/ChangeInImplicitDSOLinking.