Fortran coarray collectives: non-coarray write visibility across images without sync memory
Symptom Portable reasoning about data visibility after a collective subroutine (co_sum, co_max, co_min, co_reduce) is hindered because the Fortran 2018 standard specifies an implicit synchronization but does not mandate whether that synchronization acts as a full memory fence equivalent to sync memory . Context Current compilers diverge: GNU Fortran 12+ trea