High Performance Fortran (HPF) history and lessons

@sblionel and any and all readers working on orgs such as WG5 or in the Community toward an official / unofficial charter to advance Fortran as a language, please pay attention to this note and read carefully.

First, Fortran language bearers need a vision to make Fortran the lingua franca of scientific and technical computing. Toward this, as mentioned by @certik and others here and elsewhere, not only processors but the entire tooling options and ecosystem are critically important. Toward this, everyone should ask themselves: how inconvenient or difficult is it to develop such tooling using the Fortran language itself? For example, can one productively bootstrap an entire Fortran compiler and continue to enhance and maintain it using a base language set e.g., Fortran 2018? If not (and the answer in year 2020 is indeed that it is not), that has gotta be a realization there are serious deficiencies and those gaps need to be addressed. The vision has to a language such that everyone, at least in principle if not always in practice, can do all the needed tooling using the language itself.
Another crucial aspect of the language vision is to consider library development. Libraries are of utmost importance to all domains, but especially so in scientific and technical computing. It gets to the core of how science, especially the third leg now which is computational science to complement theory and experiments, advances - brick-by-brick and upon the shoulders of others. How easy and convenient is to develop libraries in Fortran that can used effectively and productively by the broader scientific and technical community? In year 2020, the reality is it is extremely difficult, impossible even in some situations. This extends to both standard libraries as well as other community / domain-specific libraries. The issues here are another indicators of where the language needs to improve.

With the above vision in mind, here’re the specifics for the base language itself to improve library and toolset development:

  1. Unsigned integers or bitset type,
  2. Proper enumeration type along the lines of Swift (preferably), or at least C++ / D,
  3. Improved support for OO paradigm including easier static casting and to be able to SEAL classes (mark them as final)
  4. Improved Generics and template programming including utilities that enable robust new containers and algorithms. This includes facilities such as iterators and being able to overload “operators” such N:M for array sections.
  5. Anonymous functions (lambda operations) and closures,
  6. Exception handling

The above list is not too long, it can be achieved with some focus and attention, especially toward the vision.

If this is achieved, it will truly open up Fortran to a new world of libraries (a la Kokkos in C++ for GPUs) and it will enable Fortran to remain agnostic to hardware and other combined hardware-software trends.