Hi, As far as I know, the message transfer knowledge of OpenMPI when using PML/UCX is pretty minimal. When sending a message, the arguments are passed to UCX as is (here https://github.com/open-mpi/ompi/blob/main/ompi/mca/pml/ucx/pml_ucx.c#L840) The UCX tag is a combination of MPI tag and communicator context id (https://github.com/open-mpi/ompi/blob/main/ompi/mca/pml/ucx/pml_ucx_request.h#L46) There also is a variant using ucp_tag_send_nbx, which seems similar.
If you want to understand how the message is matched and segmented or if there is any header and what's in it, you may want to check the UCP (UCX Protocols) part of UCX. Regards, Florent -----Message d'origine----- De : devel <devel-boun...@lists.open-mpi.org> De la part de Kingshuk Haldar via devel Envoyé : lundi 31 juillet 2023 09:37 À : devel@lists.open-mpi.org Cc : Kingshuk Haldar <kingshuk.hal...@hlrs.de> Objet : [OMPI devel] Requesting information for message envelope/metadata Caution: External email. Do not open attachments or click links, unless this email comes from a known sender and you know the content is safe. Hi, I need to access the message envelope/metadata structure that is sent along with/before the message is sent to UCX completely. Is this available at the OpenMPI code or, is now completely passed to the UCX now? I tried to figure it out myself but got lost. Any help is appreciated. Best, Kingshuk -- Kingshuk Haldar email: kingshuk.hal...@hlrs.de HLRS, Uni Stuttgart https://www.hlrs.de/people/kingshuk-haldar Nobelstraße 19 phone: +49 711 685 62023 70569 Stuttgart, Germany
