On Jul 16, 2016, at 2:57 AM, Christian Grün <christian.gruen@gmail.com> wrote:

Hi Carl,

Thanks again for your observation! Only now, I noticed that
xquery:fork-join did weird things when specifying an empty sequence as
argument.

This has been fixed [1]; without the latest snapshot [2], you can get
rid of the "where $c_orgs" clause.

I tried your original fork query, and it now terminates (it should
generate the same result as the unparallelized query after removing
the trace() within the function, or replacing it with prof:dump).

Hope this helps,
Christian

[1] https://github.com/BaseXdb/basex/commit/f7d8744e2760ed1531b48a9c9de92f3694e605b4
[2] http://files.basex.org/releases/latest



On Sat, Jul 16, 2016 at 8:38 AM, Christian Grün
<christian.gruen@gmail.com> wrote:

It seems that $c_orgs as defined in line 03 will be a single element.

Exactly. Maybe it’s sufficient to rewrite line 3 as follows:

 let $c_orgs := $orgs[parent/@id = $org_id]
 where $c_orgs


On Sat, Jul 16, 2016 at 1:16 AM, Carl Leitner <litlfred@ibiblio.org> wrote:

Hmm.  Looking at your query:
01:   declare function extractor:get_child_orgs-forked($orgs,$org) {
02:   for $org_id in $org/@id
03:   for $c_orgs in $orgs[parent/@id = $org_id]
04:   return xquery:fork-join(
05:    for $c_org in $c_orgs
06:     return function() {
07:       $c_org, extractor:get_child_orgs-forked($orgs, $c_org)
08:     }
09:   )
10:  };

This means that when you get to line 05 we are looping over a single
element and the enclosing fork-join will only be joining a single
function/thread.  Am I misreading that?

Cheers,
-carl

On Jul 15, 2016, at 5:32 PM, Christian Grün <christian.gruen@gmail.com> wrote:

Hi Carl,

Running your version of the query does not exhaust memory as mine had,
however I don’t see the CPU usage using more than one slightly more than
available processor.

Your initial fork query was creating an endless loop. In the current
one, I assume that only one function will be created for each
xquery:fork-join call. Maybe you need to spend some more time on the
question how your code could actually be forked in a recursive way at
all?

What you probably want is a xquery:fork() function (without join), but
we didn’t add such a function so far because it would be much more
difficult to eventually join the results and find a good order.

Cheers
Christian