[TUHS] Fwd: long lived programs (was Re: RIP John Backus

[Clem Cole]

[try-II]




On Fri, Mar 23, 2018 at 6:43 AM, Tim Bradshaw <tfb at tfeb.org> wrote:

> On 22 Mar 2018, at 21:05, Bakul Shah <bakul at bitblocks.com> wrote:
>
>
> I was thinking about a similar issue after reading Bradshaw's
> message about FORTRAN programs being critical to his country's
> security. What happens in 50-100 years when such programs have
> been in use for a long time but none of the original authors
> may be alive? The world may have moved on to newer languages
> and there may be very few people who study "ancient" computer
> languages and even they won't have in-depth experience to
> understand the nuances & traps of these languages well enough.
> No guarantee that FORTRAN will be in much use then! Will it be
> like in science fiction where ancient spaceships continue
> working but no one knows what to do when they break?
>
>
> My experience of large systems like this is that this isn't how they work
> at all.  The program I deal with (which is around 5 million lines naively
> (counting a lot of stuff which probably is not source but is in the source
> tree)) is looked after by probably several hundred people.  It's been
> through several major changes in its essential guts and in the next ten
> years or so it will be entirely replaced by a new version of itself to deal
> with scaling problems inherent in the current implementation.  We get a new
> machine every few years onto which it needs to be ported, and those
> machines have not all been just faster versions of the previous one, and
> will probably never be so.
>
> What it doesn't do is to just sit there as some sacred artifact which
> no-one understands, and it's unlikely ever to do so.  The requirements for
> it to become like that would be at least that the technology of large-scale
> computers was entirely stable, compilers, libraries and operating systems
> had become entirely stable and people had stopped caring about making it do
> what it does better.  None of those things seems very likely to me.
>
> (Just to be clear: this thing isn't simulating bombs: it's forecasting the
> weather.)
>

​+1 - exactly
​my ​
point.​

We have drifted a bit from pure UNIX, but I actually do think this is
relevant to UNIX history.   Once UNIX started to run on systems targeting
HPC loads where Fortran was the dominate programming language, UNIX quickly
displaced custom OSs and became the dominant target even if at the
beginning of that transition
​as ​
the 'flavor' of UNIX did vary (we probably can and should discuss how that
happened and why independently
​-- although
 I will point out the UNIX/Linux implementation running at say LLNL != the
version running at say Nasa Moffitt).    And the truth is today, for small
experiments you probably run Fortran on Windows on your desktop.   But for
'production'  - the primary OS for Fortran is a UNIX flavor of some type
and has been that way since the mid-1980s - really starting with the UNIX
wars of that time.

As I also have said here and elsewhere, while HPC and very much its
lubricant, Fortran, are not something 'academic CS types' like to study
these days
​ - even though​
 Fortran (HPC) pays my
​ and many of our​
salar
​ies​
.    Yet it runs on the system the those same academic types all prefer -
*i.e.* Ken and Dennis' ideas.    The primary difference is the type of
program the users are running.   But Ken and Dennis ideas work well for
almost all users and spans
​specific ​
application market
​s.​

Here is a
​picture
 I did a few years ago for a number of Intel exec's.  At the time I was
trying to explain to them that HPC is not a single style of application and
also help them understand that there two types of value - the code itself
and the data.  Some markets (
​*e.g.* ​
Financial) use public data but the methods they use
​to crunch it ​
(
​*i.e.* ​the
code
​s​
)
​are
 private, while others
​market segments ​
might have private data (*e.g.*
​ ​
oil and gas) but
​different customers ​
use the same or similar codes to crunch it.
​F
or this discussion, think about how much of the code I sho
​w​
below is complex arithmetics -
​while ​
much of it is searching
​ google style​
, but a lot is
​just plain ​
nasty math.   The 'nasty math' that has not changed
​over the years ​
and thus those codes are dominated by Fortran.
​ [Note Steve has pointed out that with AI maybe the math could change in
the future - but certainly so far, history of these markets is basically
differential equations solvers].​


 As Tim says, I really can not
​see ​
that changing and
​the ​
reason (I believe) is I do not see any
​compelling ​
economic reason to do so.
Clem​



ᐧ

ᐧ
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