Thanks for the reply. My query is of the type (simplified (pseudo)code):

let $u := for $r in (list of document names)

let $dirToWrite := "/directory/" || $r

return

function () {

( file:write($dirToWrite, "a=5;a"), proc:system("dir/Rscript", $dirToWrite) )

}

return

xquery:fork-join($u)

This allows me to run R scripts in parallel (which can also write something). However, if I change the content of function() with only a file:write() function (see below), it does not seem to work in parallel: do you know why?

let $u := for $r at $u in db:open("mio")

let $dirToWrite := "/directory/" || db:list("mio")[$u]

return

function () {

file:write($dirToWrite, $r)

}

return

xquery:fork-join($u)

Universität Leipzig
Institute of Computer Science, NLP
Augustusplatz 10
04109 Leipzig
Deutschland
E-mail: celano@informatik.uni-leipzig.de
E-mail: giuseppegacelano@gmail.com
Web site 1: http://asv.informatik.uni-leipzig.de/en/staff/Giuseppe_Celano
Web site 2: https://sites.google.com/site/giuseppegacelano/

On Jul 23, 2018, at 4:34 PM, Christian Grün <christian.gruen@gmail.com> wrote:

Hi again,

I am having fun with xquery:fork-join() and I see that it really reduces evaluation time (!)

Ottimo!

My computer has two cores. I was wondering what would happen if a computer had more cores/CPUs (or if the script were run on a computer cluster): could the function take advantage of all of CPUs/cores?
In the future, will there be the possibility to maybe control this via parameters to pass to the function?

Yes, more cores are supported. It may be possible to enhance the
function signature and provide options for controlling the number of
concurrent threads. Currently, we simply rely on Java’s ForkJoinPool
to distribute threads [1].

Feel free to send us the query patterns that benefit from multi-threading.

Best,
Christian

[1] https://github.com/BaseXdb/basex/blob/master/basex-core/src/main/java/org/basex/query/func/xquery/XQueryForkJoin.java