Parallel Programming Guide for HP-UX Systems

OpenMP

Implementation-deﬁned behavior

Chapter 490

11. If the dynamic threads mechanism is enabled on entering a parallel region, the allocation

status of an allocatable array that is not affected by a COPYIN clause that appears on the

region will have an initial allocation status of not currently allocated (Section 2.6.1, page

32).

12. Due to resource constraints, it is not possible for an implementation to document the

maximum number of threads that can be created successfully during a program's

execution. This number is dependent upon the load on the system, the amount of memory

allocated by the program, and the amount of implementation dependent stack space

allocated to each thread. For a 32 bit process, the stack space for each thread is allocated

from the heap. The heap defaults 1 gigabyte, and the default stacksize is 8 megabytes. See

the linker option -N for increasing data area size to 2 gigabytes.

13. If the dynamic threads mechanism is disabled, requests for additional threads will result

in no additional threads being created. Programs should not assume that a request will

result in additional threads for all requests. If the dynamic threads mechanism is

enabled, requests for more threads than an implementation can support are satisﬁed by

creating additional pthreads which are then schedule the HP-UX scheduler using a

smaller number of threads (Section 2.3.1, page 15).

14. If an OMP runtime library routine interface is deﬁned to be generic by an

implementation, use of arguments of kind other than those speciﬁed by the OMP_*_KIND

constants will likely lead to incorrect program behavior due to incorrect argument passing

for the runtime routine (Section D.3, page 111).