[CppAD] Multi-threading with TBB?

[Brad Bell]

thread_alloc::thread_num calls the function passed in thread_alloc::parallel_setup.
This is a link from the threading system to thread_alloc and the rest of CppAD.

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=
>
>     _______________________________________________
>     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=
>