[CppAD] Multi-threading with TBB?

[Perry de Valpine]

Thanks for the quick reply.

I had already been through the documentation you pointed me to.

Did my question about recording tapes vs. using tapes make sense?  The
examples seem to show each thread both recording and using its own tape.
What I understand from the documentation is that CppAD's multi-thread tools
are necessary because internally some globals are used, so CppAD needs to
be told to manage separate copies of those globals for each thread.  My
question was whether that is the case just for recording tapes or also for
using tapes, which might have been recorded and copied in serial
execution?  If my question doesn't make sense, I'd probably benefit from
any explanation you can offer.

Also can you help me understand the difference between the thread_num
function that is passed to thread_alloc::parallel_setup vs.
thread_alloc::thread_num (
https://coin-or.github.io/CppAD/doc/ta_thread_num.htm)?  Does the latter
call the former?

Thanks again.

On Wed, Dec 19, 2018 at 10:08 AM Brad Bell <bradbell at seanet.com> wrote:

> Here is the link to the key CppAD requirements for multi-threading
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__coin-2Dor.github.io_CppAD_doc_ta-5Fparallel-5Fsetup.htm&d=DwIGaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=dGUSP0mcZ-4eFJdLgjemIUFvQwbOKo1wqmE_55NIGdc&m=Uc1__A27KLDN7APwoeTDVj5NwsKADcvMO9r-o1yZWS4&s=kFwgcVYei9YZYEdnnAJfV3EyhG0Ag7dl21aNJ4w-URc&e=
>
> CppAD has to know a maximum number of threads, and which thread is
> currently running.
> It seems from
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__stackoverflow.com_questions_3786408_number-2Dof-2Dthreads-2Dused-2Dby-2Dintel-2Dtbb&d=DwIGaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=dGUSP0mcZ-4eFJdLgjemIUFvQwbOKo1wqmE_55NIGdc&m=Uc1__A27KLDN7APwoeTDVj5NwsKADcvMO9r-o1yZWS4&s=ACu19InrLSfMxKYSzdCAiytyoiclPYCkFxbTa2cJCdQ&e=
> that this is not possible in TBB, but I am not sure.
>
> On 12/19/2018 10:50 AM, Perry de Valpine wrote:
> > Hello.  I'm not sure if you prefer queries here or on GitHub.  This is a
> general question so I'm
> > sending it to this list.
> >
> > I'm trying to see whether CppAD's multi-threading features can fit well
> with Threading Building
> > Blocks (TBB).  Has anyone combined these successfully?  The simplest TBB
> example is here:
> >
> https://urldefense.proofpoint.com/v2/url?u=https-3A__software.intel.com_en-2Dus_node_506057&d=DwIGaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=dGUSP0mcZ-4eFJdLgjemIUFvQwbOKo1wqmE_55NIGdc&m=Uc1__A27KLDN7APwoeTDVj5NwsKADcvMO9r-o1yZWS4&s=U5kKsJw4CWu16GI3oMRqLsIQ2kOhjXSWiLsB0gobId8&e=
> . Since TBB abstracts away thread creation but CppAD
> > seems to require explicit thread management, I'm not sure if they're a
> natural fit for each
> > other.  I can start to see how it might be done but wanted to ask for
> any suggestions first since
> > I am relatively new to multi-threading issues.
> >
> > What I would like to do is create a tape in serial mode and then in
> parallel use multiple copies
> > of that tape. The CppAD examples all show each thread both creating and
> using a tape.   Is what I
> > want to do possible?  I would also like to do this for multiple tapes
> (of different operations)
> > that all get created once and then used repeatedly in different places.
> >
> > Based on the statements on parallel_ad (
> https://urldefense.proofpoint.com/v2/url?u=https-3A__coin-2Dor.github.io_CppAD_doc_parallel-5Fad.htm&d=DwIGaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=dGUSP0mcZ-4eFJdLgjemIUFvQwbOKo1wqmE_55NIGdc&m=Uc1__A27KLDN7APwoeTDVj5NwsKADcvMO9r-o1yZWS4&s=cxQ9bvZUkZ9p3DZ0g4O9ecRfplKTnAexABwQnXS2tpQ&e=),
>
> > which are not totally clear to me (maybe because I lack the background),
> does one need to do the
> > parallel_setup and parallel_AD steps if multiple threads will be used
> only for running tapes
> > (ADFun objects) but not making new tapes?
> >
> > Thanks for the great software.
> >
> > Perry
> >
> >
> >
> > _______________________________________________
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> > CppAD at list.coin-or.org
> >
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