You will need to create a special variable that holds 2 entries, one for the max operation (with whatever type you need) and an int for the rank of the process. The MAXLOC is described on the OMPI man page [1] and you can find an example on how to use it on the MPI Forum [2].
George. [1] https://www.open-mpi.org/doc/v2.0/man3/MPI_Reduce.3.php [2] https://www.mpi-forum.org/docs/mpi-1.1/mpi-11-html/node79.html On Fri, Aug 10, 2018 at 11:25 AM Diego Avesani <diego.aves...@gmail.com> wrote: > Dear all, > I have probably understood. > The trick is to use a real vector and to memorize also the rank. > > Have I understood correctly? > thanks > > Diego > > > On 10 August 2018 at 17:19, Diego Avesani <diego.aves...@gmail.com> wrote: > >> Deal all, >> I do not understand how MPI_MINLOC works. it seem locate the maximum in a >> vector and not the CPU to which the valur belongs to. >> >> @ray: and if two has the same value? >> >> thanks >> >> >> Diego >> >> >> On 10 August 2018 at 17:03, Ray Sheppard <rshep...@iu.edu> wrote: >> >>> As a dumb scientist, I would just bcast the value I get back to the >>> group and ask whoever owns it to kindly reply back with its rank. >>> Ray >>> >>> >>> On 8/10/2018 10:49 AM, Reuti wrote: >>> >>>> Hi, >>>> >>>> Am 10.08.2018 um 16:39 schrieb Diego Avesani <diego.aves...@gmail.com>: >>>>> >>>>> Dear all, >>>>> >>>>> I have a problem: >>>>> In my parallel program each CPU compute a value, let's say eff. >>>>> >>>>> First of all, I would like to know the maximum value. This for me is >>>>> quite simple, >>>>> I apply the following: >>>>> >>>>> CALL MPI_ALLREDUCE(eff, effmaxWorld, 1, MPI_DOUBLE_PRECISION, MPI_MAX, >>>>> MPI_MASTER_COMM, MPIworld%iErr) >>>>> >>>> Would MPI_MAXLOC be sufficient? >>>> >>>> -- Reuti >>>> >>>> >>>> However, I would like also to know to which CPU that value belongs. Is >>>>> it possible? >>>>> >>>>> I have set-up a strange procedure but it works only when all the CPUs >>>>> has different values but fails when two of then has the same eff value. >>>>> >>>>> Is there any intrinsic MPI procedure? >>>>> in anternative, >>>>> do you have some idea? >>>>> >>>>> really, really thanks. >>>>> Diego >>>>> >>>>> >>>>> Diego >>>>> >>>>> _______________________________________________ >>>>> users mailing list >>>>> users@lists.open-mpi.org >>>>> https://lists.open-mpi.org/mailman/listinfo/users >>>>> >>>> _______________________________________________ >>>> users mailing list >>>> users@lists.open-mpi.org >>>> https://lists.open-mpi.org/mailman/listinfo/users >>>> >>> >>> _______________________________________________ >>> users mailing list >>> users@lists.open-mpi.org >>> https://lists.open-mpi.org/mailman/listinfo/users >>> >> >> > _______________________________________________ > users mailing list > users@lists.open-mpi.org > https://lists.open-mpi.org/mailman/listinfo/users
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