[ic] Iterations slow with mv_matchlimit incrementations

Gert van der Spoel gert at 3edge.com
Tue May 12 06:50:22 UTC 2009

> -----Original Message-----
> From: interchange-users-bounces at icdevgroup.org [mailto:interchange-
> users-bounces at icdevgroup.org] On Behalf Of Grant
> Sent: Tuesday, May 12, 2009 9:16 AM
> To: interchange-users at icdevgroup.org
> Subject: Re: [ic] Iterations slow with mv_matchlimit incrementations
> >>> I have a somewhat complex chunk of IC code about 500 lines long.
> >>> If I
> >>> set the mv_matchlimit of the main loop to a small number, each
> >>> iteration takes less than a second to execute.  However, as I
> >>> increase
> >>> the mv_matchlimit, each iteration takes longer to execute until
> it's
> >>> quite slow.  I've been over my code again and again but I can't
> >>> find a
> >>> cause for this behavior.  The only clue I have is that each
> iteration
> >>> executes much faster when the loop is almost done with all of its
> >>> iterations.
> >>>
> >>> I'm wondering if the problem is "under the hood" of IC.  Does this
> >>> scenario ring a bell for anyone?
> >>>
> >>> Thanks,
> >>> Grant
> >>
> >> I'm baffled by this.  I have no idea why increasing mv_matchlimit
> >> would drastically increase the amount of time required for *each*
> loop
> >> iteration.  Please let me know if you have any ideas.
> >
> > Is there any way you can post the relevant piece of code?  Without
> > knowing what's being iterated over, it's hard to offer suggestions.
> > In particular, are there any parts which are perl blocks of any
> > particular flavor (calc, calcn, perl, prefix-exec, etc)?  Are there
> > perhaps multiple nested loop constructs?
> >
> > Regards,
> >
> > David
> Here's another illustration of my problem.  I set up 15 [email] tags
> throughout my code so I get an email whenever certain points are
> reached.  With ml=10 I get maybe 20 or so emails per second.  With
> ml=999999 I get much less than 1 email per second.  My understanding
> is that the first 10 iterations should take the same amount of time in
> either scenario.
> Does anyone know why IC would execute a single iteration at a
> drastically slower rate, just because it has more total iterations to
> execute?
> My installation is a year or two old.  Does this sound like a problem
> an upgrade could fix?

e-mail does not seem to be the most useful medium to do performance tests.
Servers can start holding e-mails or other external influences can cause
e-mails to arrive less frequently.

Why not have 15 timestamps written to a logfile, so you can look at this
data and see if you can find any trends. Is it that the 15 timestamps are
increasing in interval equally?
So it was with 
ml=10:   time,  time+I,   time+I+I,  time+I+I+I    (10, 15, 20, 25 etc)
ml=999999:   time,   time+(Ix10),  time+(Ix10+Ix10),  time+(Ix10+Ix10+Ix10)
(10, 60, 110, 160 etc)

or does ml=999999  show a less regular pattern where it has a spike between
two timings?

But you can imagine that it is shooting in a black hole here without
actually seeing the code.



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