Re: [Plplot-devel] plinit, plend, plinit sequence now works, but I am having second thoughts

[Joao C. <jc...@fe...>]

On Tuesday 10 December 2002 08:07, Alan W. Irwin wrote:
> Apparently Joao has sequences of plinit, plend, plinit in his "x" octav=
e
> examples which violated an assumption I had made that a call to plend w=
as
> the last possible use of libplplot in a programme.  With that assumptio=
n I
> could release libltdl memory resources in plend.  I have now fixed this=
 so
> the libtldl memory resources are never released.  Now on my system all =
of
> Joao's "x" examples run and all his "p" examples also run except for p7=
 and
> p15. Apparently Joao knows what the p7 trouble is so that leaves only p=
15
> as the last octave example where there is unexplained trouble.
>
> This is a nice step forward, but nevertheless, I am now having second
> thoughts about this "fix" because I like the idea of plend being the la=
st
> possible call to the libplplot library so we could release all dynamic
> driver (and in my case the libltdl) memory resources there.  Those are =
the
> memory resources that are allocated when the library is initialized so =
this
> is the only possible place to release the resources again.  But that ca=
nnot
> be done if our users are free to call plinit again after plend is calle=
d.
>
> I would like to hear the developer's thoughts (especially Joao's though=
ts)
> on this topic. For example, there should be a way for the octave x exam=
ples
> to work using pladv without having to call any libplplot function after
> plend is called at the very end of the x plots.  I assert that because =
all
> the normal x examples in C are done that way so I assume octave can fol=
low
> that model.

That is not the problem. The problem is an user program finish doing a pl=
ot,=20
and thus closing the plot using plend(). Latter on, in the same program,=20
another plot is needed, thus plinit() is again called.
The x??c examples all finish with plend(), thus the octave counterparts a=
lso=20
do the same. But *one* instance of Octave wants to run *all* x??c demos, =
thus=20
the several plinit/plend.

I often do that in Octave, closing a plot figure, opening another, ... an=
d all=20
users of interactive languages certainly do the same. Of course, I could =
use=20
plinit/plend1(), but then, when would I call plend()? I really never know=
=20
when the user has finished opening/closing plot windows or finished using=
=20
Octave (*).

I never bother releasing memory that will be relased anyway by the OS whe=
n a=20
program finish. At least in unix, when a program finish, the memory owned=
 by=20
the program will be released.

Joao

(*)- I could register with atexit() a function that would do the cleanup,=
 but=20
what for? The OS does it for me.

> Alternatively, there is the python or tcl model where plinit is
> called once before all examples are plotted, every example restores ini=
tial
> values (colour maps) when its part of the plotting is done, and plend i=
s
> called once at the end (see xw??.py and pythondemos.tcl to see how this
> approach all fits together).  Could that "python" approach work for oct=
ave,
> Joao?
>
> Alan
>
> email: ir...@be...
> phone: 250-727-2902=09FAX: 250-721-7715
> snail-mail:
> Dr. Alan W. Irwin
> Department of Physics and Astronomy,
> University of Victoria, P.O. Box 3055,
> Victoria, British Columbia, Canada, V8W 3P6
> __________________________
>
> Linux-powered astrophysics
> __________________________
>
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by:ThinkGeek
> Welcome to geek heaven.
> http://thinkgeek.com/sf
> _______________________________________________
> Plplot-devel mailing list
> Plp...@li...
> https://lists.sourceforge.net/lists/listinfo/plplot-devel