> $ j -js "exit echo 2 [ (fork&cd bind '') '' [ load
> 'data/jd/server/fork'"
> 2
> 2
It seems to me that the above construction works for the UNIX family but
not for Windows; at least, I managed to run a version of the above in a
very basic BusyBox system but I could not figure out how to run a
version of it in Windows 10. Am I wrong? (Admittedly, my knowledge
regarding this matter is very limited.)
> Practical, non-destructive use fork probably has a bunch of caveats,
> but it does also in C programs.
Imagine, for instance, that one wants to evaluate hundreds of times an
expensive arbitrary verb (u), that takes minutes to produce a single value,
to plot the verb. In an ideal J world, u("_1) or u(&.>) could be used to
run the evaluations in parallel in minutes as opposed to run them serially
in hundreds of minutes. Back to reality, I can find (I think) a cumbersome
way, using fork_jtask_, to save significant time when the computer has a
multi-core processor running Windows or a UNIX family OS. However, I
wonder how the experts would attack this kind of problem...
On Thu, Apr 1, 2021 at 6:12 PM Julian Fondren <[email protected]>
wrote:
>
> A fork bomb is more suited to POSIX fork, which J can use:
>
> NB. you might have to reboot if you run this
> load 'data/jd/server/fork'
> [ F. (fork&cd bind '') ''
>
> Tested separately:
>
> $ j -js "exit echo 2 [ (fork&cd bind '') '' [ load
> 'data/jd/server/fork'"
> 2
> 2
>
> echoing 2 twice, from the two J processes, before they both exit.
>
> [ F. (echo bind 2) ''
>
> echoing 2 until interrupted.
>
>
> Practical, non-destructive use fork probably has a bunch of caveats,
> but it does also in C programs.
>
> On 2021-04-01 16:08, Jose Mario Quintana wrote:
> > Personally, I prefer the version where although the life of the
> > individuals
> > is ephemeral the species survives a lot longer, as it occurs in nature.
> > Either way, looking at the structure of the verb fork_jtask_ and its
> > components, it seems to me that this is a kind of task far more
> > suitable to
> > C than J.
> >
> >
> >
> > On Wed, Mar 31, 2021 at 10:17 PM Raul Miller <[email protected]>
> > wrote:
> >
> >> Sure, and here's a c program which will run into similar resource
> >> limits:
> >>
> >> main() {
> >> while (1) {
> >> fork();
> >> }
> >> }
> >>
> >> This issue was probably one of the motivations for the ulimit command
> >> (which people almost never use, nowadays, because we have long since
> >> learned to expect distributed programs to be well behaved).
> >>
> >> Take care,
> >>
> >> --
> >> Raul
> >>
> >> On Wed, Mar 31, 2021 at 6:39 PM Jose Mario Quintana
> >> <[email protected]> wrote:
> >> >
> >> > For some reason, probably the pandemic, recent posts regarding the
verb
> >> > fork_jtask_ evoked old memories. In the late '70s, while reading a
> >> passage
> >> > in a book describing Von Newman's scheme for constructing
> >> self-replicating
> >> > machines, I realized I could design a self-replicating process
capable of
> >> > running in the computer environment at work. The computer was a
> >> Burroughs
> >> > B6700 and it had enabled the Inter Process Communication (IPC)
facility
> >> > which allowed a process to run another process. I wrote a tiny
program
> >> and
> >> > showed it as a curiosity to a few of my colleagues telling them that
it
> >> > would likely overwhelm the computer; but, for the same reason, I
could
> >> not
> >> > test it.
> >> >
> >> > Shortly after I went to work for another institution and, in the
early
> >> > '80s, I moved from Mexico to England and I bought a little
microcomputer
> >> > called Sinclair QL. It had a multitasking OS called QDOS and a BASIC
> >> > variant called SuperBASIC which was also the QDOS' command-line
> >> > interpreter. So, I rewrote and ran a version of my tiny program
and, as
> >> > expected, the only way out was to, literally, pull-the-plug.
> >> > (Incidentally, the machine which looked almost like a keyboard was
also
> >> > capable to run QL APL, which was a special version of MicroAPL's
> >> APL.68000.)
> >> >
> >> > I had swamped not only j but also the OS a few times before, but
never
> >> > intentionally. So, this is a first for me, the following fleeting
> >> > script (beware of line-wrapping) runs in an earlier custom version of
> >> the j
> >> > interpreter on Windows 10 but it should be able to run in the latest
and
> >> > greatest public versions of j and also on other platforms (changing
what
> >> > needs to be changed); however, my strong advice, unless one likes to
live
> >> > dangerously, is:
> >> >
> >> > DO NOT RUN IT!
> >> >
> >> > NB. Saved as J:/temp/Virus.ijs
> >> >
> >> > (2!:55)@:_:@:(([fork_jtask_)^:2) '"J:/Program Files/J/bin/jqt.exe"
> >> > "J:/temp/Virus.ijs"'
> >> >
> >> >
> >> > PS. Many years later while visiting an old friend in New York, who
used
> >> to
> >> > be a member of the staff operating the B6700, he told me that one of
the
> >> > most stressful times ever at work was when the B6700 suddenly kept
> >> crashing
> >> > and crashing for a few days, even missing a payroll deadline. The
staff
> >> > and the Burroughs technicians could not find anything wrong with the
> >> > hardware. The issue was that the system was too clever, after a
crash it
> >> > would automatically restart all the processes which were interrupted.
> >> > Immediately after identifying the culprit, the sneaky tiny program
which
> >> > was very familiar to me, the general access to the IPC facility was
> >> > disabled...
> >> >
> >> > Long live the verb fork_jtask_! :)
> >> >
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http://www.jsoftware.com/forums.htm
> >> ----------------------------------------------------------------------
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> >>
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