Re: turn off garbage collector?

From: Joachim Schimpf <>
Date: Fri 24 May 2002 10:01:45 PM GMT
Message-ID: <>
Sebastian Sardina wrote:
> I have a very simple question: I have a predicate, say a/3, that is
> usually very time-consumming. However, it runs much faster if I turn off
> the garbage collector (GC)

Before switching the GC off completely, consider the following:

- if you are running an Eclipse < 5.3, you should upgrade.
  Newer versions have a different default GC triggering policy
  (controlled by the gc_policy flag) which should keep the overhead

- the GC triggering interval is determined by the flag gc_interval
  (see get_flag/2,set_flag/2). If you increase this number, the GC
  will trigger less often and use less time. The default setting is
  a fraction of the initial global/trail stack limit ( -g option in
  the command line eclipse, or preference setting in tkeclipse).

> My question is: how should I do to turn the gc off first, call a/3, and
> then turn the gc on again and still be "safe". Should I call the
> GC explicitely after a/3 has finished or is it sufficient to turn the
> flag on again? Something like:
> main:- ......,
>         set_flag(gc,off),  % Switch off GC
>         a(..,..,..),       % Call a/3
>         set_flag(gc,on),
>         main.
> After A is executed the GC is turned on. Is that ok or should I do
> something else? Is it the case that a/3 may have left a lot of "garbage"
> or does everything cleans up when a/3 succeeds?

set_flag(gc,on) will not necessarily cause the GC to run.
You need to call garbage_collect/0 as well.

 Joachim Schimpf              /             phone: +44 20 7594 8187
 IC-Parc, Imperial College   /  
 London SW7 2AZ, UK         /
Received on Fri May 24 23:01:53 2002

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