sure the data have arrived. ! I/O from all images, executing in any order, but each record written is intact. write(*,'(3a,i0)') 'Hello ',trim(name),' from image ', this_image() end program Hello_world The program above scales poorly because the loop that distributes information executes sequentially. Writing scalable programs often requires a sophisticated understanding of parallel algorithms, a detailed knowledge of the underlying network characteristics, and special tuning for application characteristics such as the size of data transfers. For most application developers, letting the compiler or runtime library decide the best algorithm proves more robust and high-performing. Fortran 2018 will offer collective communication subroutines that empower compiler and runtime library teams to encapsulate efficient parallel algorithms for collective communication and distributed computation in a set of collective subroutines. These subroutines and other new parallel programming features are summarized in a technical specification that the Fortran standards committee has voted to incorporate into Fortran 2018. These enable the user to write a more efficient version of the above algorithm program Hello_World implicit none character(len=20) :: name[*] ! scalar coarray, one "name" for each image. ! Note: "name" is the local variable while "name[<index>]" accesses the ! variable in a specific image; "name[this_image()]" is the same as "name". ! Interact with the user on Image 1; execution for all others pass by. if (this_image() == 1) then write(*,'(a)',advance='no') 'Enter your name: ' read(*,'(a)') name end if ! Distribute information to all images call co_broadcast(name,source_image=1) ! I/O from all images, executing in any order, but each record written is intact. write(*,'(3a,i0)') 'Hello ',trim(name),' from image ', this_image() end program Hello_world where the lack of explicit synchronization offers the potential for higher performance due to less coordination between the images. Furthermore, TS 18508 guarantees that "A transfer from an image cannot occur before the collective subroutine has been invoked on that image." This implies some partial synchronization inside co_broadcast, but could be higher performing than the "sync all" in the prior example. TS 18508 also incorporates several other new features that address issues targeted by the CAF 2.0 effort described below. Examples include teams of images and events. An alternate perspective In 2011, Rice University pursued an alternate vision of coarray extensions for the Fortran language. Their perspective is that the Fortran 2008 standard committee's design choices were shaped more by the desire to introduce as few modifications to the language as possible than to assemble the