[Cython] cython.parallel tasks, single, master, critical, barriers
mark florisson
markflorisson88 at gmail.com
Sun Oct 9 14:11:56 CEST 2011
Hey,
So far people have been enthusiastic about the cython.parallel features, I
think we should introduce some new features. I propose the following, assume
parallel has been imported from cython:
with parallel.master():
this is executed in the master thread in a parallel (non-prange) section
with parallel.single():
same as master, except any thread may do the execution
An optional keyword argument 'nowait' specifies whether there will be a
barrier at the end. The default is to wait.
with parallel.task():
create a task to be executed by some thread in the team
once a thread takes up the task it shall only be executed by that thread
and no other thread (so the task will be tied to the thread)
C variables will be firstprivate
Python objects will be shared
parallel.taskwait() # wait on any direct descendent tasks to finish
with parallel.critical():
this section of code is mutually exclusive with other critical sections
optional keyword argument 'name' specifies a name for the critical
section,
which means all sections with that name will exclude each other, but not
critical sections with different names
Note: all threads that encounter the section will execute it, just not
at the same time
with parallel.barrier():
all threads wait until everyone has reached the barrier
either no one or everyone should encounter the barrier
shared variables are flushed
Unfortunately, gcc again manages to horribly break master and single
constructs in loops (versions 4.2 throughout 4.6), so I suppose I'll first
file a bug report. Other (better) compilers like Portland (and I'm sure
Intel) work fine. I suppose a warning in the documentation will suffice
there.
If we at some point implement vector/SIMD operations we could also try out
the Fortran openmp workshare construct.
What do you guys think?
Mark
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