Hi Bruce, Try configure mpich using --with-device=ch4:ofi --enable-extended-context-bits. Hui ________________________________ From: Palmer, Bruce J via discuss <[email protected]> Sent: Thursday, October 3, 2024 11:44 AM To: [email protected] <[email protected]> Cc: Palmer, Bruce J <[email protected]> Subject: [mpich-discuss] Maximum number of communicators Hi, I’m looking at using MPI RMA to support sparse data structures in Global Arrays. I’ve got an application that uses a large number of sparse arrays and it is failing when the number of sparse arrays reaches about 500. Each sparse array is ZjQcmQRYFpfptBannerStart This Message Is From an External Sender This message came from outside your organization. ZjQcmQRYFpfptBannerEnd Hi, I’m looking at using MPI RMA to support sparse data structures in Global Arrays. I’ve got an application that uses a large number of sparse arrays and it is failing when the number of sparse arrays reaches about 500. Each sparse array is built on top of 4 conventional global arrays and each global array uses one MPI Window. Each Window appears to be creating its own communicator and I’m hitting an internal limit at 2048 communicators. Is there a way to increase the number of communicators? Bruce Palmer