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ta_parallel_setup¶
View page sourceSetup thread_alloc For Use in Multi-Threading Environment¶
Syntax¶
thread_alloc::parallel_setup( num_threads , in_parallel , thread_num )
Purpose¶
By default there is only one thread and all execution is in sequential mode, i.e., multiple threads are not sharing the same memory; i.e. not in parallel mode.
Speed¶
It should be faster, even when num_thread is equal to one,
for thread_alloc to hold onto memory.
This can be accomplished using the function call
thread_alloc::hold_memory(true)
see hold_memory .
num_threads¶
This argument has prototype
size_tnum_threads
and must be greater than zero. It specifies the number of threads that are sharing memory. The case num_threads == 1 is a special case that is used to terminate a multi-threading environment.
in_parallel¶
This function has prototype
boolin_parallel (void)
It must return true if there is more than one thread
currently executing.
Otherwise it can return false.
In the special case where num_threads == 1 , the routine in_parallel is not used.
thread_num¶
This function has prototype
size_tthread_num (void)
It must return a thread number that uniquely identifies the currently executing thread. Furthermore
0 <= thread_num () < num_threads
. In the special case where num_threads == 1 , the routine thread_num is not used.
Note that this function is called by other routines so, as soon as a new thread is executing, one must be certain that thread_num () will work for that thread.
Restrictions¶
The function parallel_setup must be called before
the program enters parallel execution mode.
In addition, this function cannot be called while in parallel mode.
Example¶
The files openmp_get_started.cpp , bthread_get_started.cpp , and pthread_get_started.cpp , contain examples and tests that use this function.