[GAP Forum] Run GAP command for x seconds

[Carl-Fredrik Nyberg Brodda (MTH - Postgraduate Researcher)]

Dear Frank, Christopher, Forum,

Thank you both for your extensive help. All is working now as I need it!

Best,
Carl-Fredrik
________________________________
From: Frank Lübeck <frank.luebeck at math.rwth-aachen.de>
Sent: Thursday, January 28, 2021 1:26 PM
To: Carl-Fredrik Nyberg Brodda (MTH - Postgraduate Researcher) <C.Nyberg-Brodda at uea.ac.uk>
Cc: forum at gap-system.org <forum at gap-system.org>
Subject: Re: [GAP Forum] Run GAP command for x seconds

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On Thu, Jan 28, 2021 at 10:31:28AM +0000, Carl-Fredrik Nyberg Brodda (MTH - Postgraduate Researcher) wrote:
> Chris: I cannot seem to load the function IO_CallWithTimeout, or indeed
> IO_CallWithTimeoutList -- there seems to be no function with this name. I
> have IO 4.5.2 loaded.

Dear Carl-Frederik, dear Forum,

The functions IO_CallWithTimeout and IO_CallWithTimeoutList are pretty new
and mainly for convenience with respect to specifying the time, they just
call ParDoByFork.

> Frank: Your code runs fine, but when I run e.g the following code
> > ParTakeFirstResultByFork([function(x) local F; F := FreeGroup(x); return
> F; end], [[1]],rec(TimeOut :=rec(tv_sec :=2, tv_usec := 0 )));
>
> this makes my GAP go haywire and totally breaks it,
> [...]

There is a limitation in the kind of return values of the called functions.
GAP must be able to encode (serialize) any return value with IO_Pickle
and decode it with IO_Unpickle (this is how the forked child process
transfers its result to the parent process).

Unfortunately, a free group which is returned by your simple function
is not among the supported objects. See
  ?IO_Pickle
for more details.

Best regards again,
   Frank

--
///  Dr. Frank Lübeck, Lehrstuhl für Algebra und Zahlentheorie,
\\\  Pontdriesch 14/16, 52062 Aachen, Germany
///  E-mail: Frank.Luebeck at Math.RWTH-Aachen.De
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