Dear sessions-group, is there any information about the usage of MPI_Buffer_attach, MPI_Buffer_detach and MPI_Bsend for applications that use the world model together with (several) sessions. MPI-4.0, the function index entries of MPI_Buffer_attach and the corresponding texts do not give an answer, or do they? Is it allowed or intended that two MPI_Bsend calls with two different communicators derived not from the same session or world may use portions of the same buffer that was attached with MPI_Buffer_attach? Is there any issue or pull request already for this problem prepared? Or slides in previous meetings? Best regards Rolf -- Dr. Rolf Rabenseifner . . . . . . . . . .. . . [email protected] . High Performance Computing Center (HLRS) . . . ++49(0)711/685-65530 . University of Stuttgart . . . . . . www.hlrs.de/people/rabenseifner . Nobelstr. 19, 70569 Stuttgart, Germany