My home-made parallelization routines spin off multiple copies of J, not using fork explicitly, but it does give significant performance improvement. It's very simple but works well enough on multi-cores that I've never been motivated enough to try to improve it.
On Tue, Apr 6, 2021 at 7:47 PM Jose Mario Quintana < [email protected]> wrote: > > $ 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_! :) > > >> > > ---------------------------------------------------------------------- > > >> > For information about J forums see > http://www.jsoftware.com/forums.htm > > >> ---------------------------------------------------------------------- > > >> For information about J forums see > http://www.jsoftware.com/forums.htm > > >> > > > ---------------------------------------------------------------------- > > > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > -- Devon McCormick, CFA Quantitative Consultant ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
