OpenSHMEM Application Programming Interface, Version 1.4
Major changes in OpenSHMEM 1.4 include multithreading support, contexts for communication management, shmem_sync, shmem_calloc, expanded type support, a new namespace for atomic operations, atomic bitwise operations, shmem_test for nonblocking point-to-point synchronization, and C11 type-generic interfaces for point-to-point synchronization.
For a detailed list of changes, please refer to Annex G in the OpenSHMEM 1.4 specification document.