[CppAD] Multi-threading with TBB?

Wed Dec 19 20:52:20 EST 2018

Thanks for the support.

On Wed, Dec 19, 2018 at 1:08 PM Brad Bell <bradbell at seanet.com> wrote:

> One needs a separate copy of a tape for each thread.
> This is because there is information stored along with the operation
> sequence that is the tape.
>
> It is possible to make one tape recording, then make multiple copies of
> the tape using the
> assignment operator
> http://coin-or.github.io/CppAD/doc/funconstruct.htm#Assignment%20Operator
> Then uses a separate copy for each thread.
>
> On 12/19/2018 12:11 PM, Perry de Valpine wrote:
> > 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 <mailto:
> 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
> >     >
> >     >
> >     >
> >     > _______________________________________________
> >     > CppAD mailing list
> >     > CppAD at list.coin-or.org <mailto:CppAD at list.coin-or.org>
> >     >
> >
> https://urldefense.proofpoint.com/v2/url?u=https-3A__list.coin-2Dor.org_mailman_listinfo_cppad&d=DwIGaQ&c=Ngd-ta5yRYsqeUsEDgxhcqsYYY1Xs5ogLxWPA_2Wlc4&r=dGUSP0mcZ-4eFJdLgjemIUFvQwbOKo1wqmE_55NIGdc&m=Uc1__A27KLDN7APwoeTDVj5NwsKADcvMO9r-o1yZWS4&s=t3fua1j4WWrTlEaRrF1uxB5fhl6ha4p8-fOBdGdKc8s&e=
> >
> >     _______________________________________________
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> >
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> >
>
>
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