New subject: local allocation in ConTeXt

24 Jan 2017

      Dear Hans,

thank you very much for helping me out here.

Aditya's rephrasal of the question might have shown a tree but hidden 
the forest ... ;-)  Let me try to explain below, but please also take a 
look at my original post, 
https://mailman.ntg.nl/pipermail/dev-context/2016/003346.html.

As far as I can see, in your 10 million example I can only work on one 
of the local boxes at the time, whereas I need to save an undetermined 
number of boxes, do some computation which uses dimensions of all these 
boxes (this computation potentially invokes user's code, so I don't have 
control over it), and then use all the saved boxes.
(Btw, saving just the dimensions is not an acceptable solution, both 
because of speed and because in general, setting the box with same 
content twice won't yield the same result.)

As the number of needed boxes cannot be known in advance, I'd like to be 
nice and "give them back" to the allocation system after using them. And 
I *do* know how to do that (see localloc, elocalloc, or etex), but I'm 
not sure if it would cause any trouble in ConTeXt: I'd prefer "not to 
mess with allocation" indeed and have the issue fixed systemically.
...
The overhead is just one box per name and you probably don't allocate 
a million unique tempboxes as you will then already ran out of names.
I believe this overhead is precisely what I'm trying to avoid. A further 
detail of my situation might help. I've got, for each node of the tree:
\locbox\tempbox
\setbox\tempbox\hbox{...}
\expandafter\let\csname node<id>@box\endcsname\tempbox
...
Messing with the allocation can fail because when the content of the
boxes triggers a new box allocation itself that one might be forgotten
as well.
I'm not sure I get this. Even if the new box allocation was global (so, 
the usual \newbox)?
Best,
Sašo

P.S. And I did test it! Albeit with two iterations, not ten million. ;-)

On 24. 01. 2017 13:48, Hans Hagen wrote:
...
On 1/24/2017 10:47 AM, Sašo Živanović wrote:
...
I'm afraid this doesn't do the trick: \c_syst_last_allocated_box is
definitely incremented.
Let me try explaining again. This is essentially what I do:
{
  \newbox\TempBox
  \setbox\TempBox\hbox{Box One}
  \let\BoxOne\TempBox
  \global\let\TempBox\relax
\newbox\TempBox
  \setbox\TempBox\hbox{Box Two}
  \let\BoxTwo\TempBox
  \global\let\TempBox\relax
\the\numexpr\BoxOne: [\box\BoxOne]
  \the\numexpr\BoxTwo: [\box\BoxTwo]
}
But I want the number of available box registers at entering and exiting
the group to be the same, and substituting \newbox for \locbox is what
does the trick in my package. So I can run the following a million times:
{
  \newlocalbox\TempBox
  \setbox\TempBox\hbox{Box One}
  \let\BoxOne\TempBox
  \global\let\TempBox\relax
\newlocalbox\TempBox
  \setbox\TempBox\hbox{Box Two}
  \let\BoxTwo\TempBox
  \global\let\TempBox\relax
\the\numexpr\BoxOne: [\box\BoxOne]
  \the\numexpr\BoxTwo: [\box\BoxTwo]
}
Each of the million "\the\numexpr\BoxOne" should produce the same
number, whereas in the \newbox-based example these numbers increment.
I suppose you didn't test it ...
\starttext
% \unprotect
%
% \installcorenamespace{localbox}
%
% \unexpanded\def\newlocalbox#1%
%   {\expandafter\let\expandafter#1\csname\??localbox\string#1\endcsname
%    \ifx#1\relax
%      \syst_aux_new_localbox#1%
%    \fi}
%
% \def\syst_aux_new_localbox#1%
%   {\expandafter\newbox\csname\??localbox\string#1\endcsname
%    \newlocalbox#1}
%
% \protect
\newbox\MyBoxA \number\MyBoxA
\dorecurse{10} {
    \dorecurse{1000000} {
        \newlocalbox\TempBox
    }
    \writestatus{!!!}{#1 million done}
    #1: \number\TempBox\par
}
\newbox\MyBoxB \number\MyBoxB
\stoptext
The overhead is just one box per name and you probably don't allocate a
million unique tempboxes as you will then already ran out of names.
Messing with the allocation can fail because when the content of the
boxes triggers a new box allocation itself that one might be forgotten
as well.
...
Best,
Sašo
On 24. 01. 2017 09:52, Hans Hagen wrote:
...
...
You are asking how to define a macro, \locbox, such that the following
code should not change the value of \c_syst_last_allocated_box.
\bgroup
\locbox\BoxOne
\locbox\BoxTwo
\BoxOne\hbox{Box One}
\BoxTow\hbox{Box Two}
% Do some measurement based on the size of the boxes
\egroup
The fact that a LaTeX package implements this behaviour by allocating
local box numbers from the end seems to be an implementation detail.
I don't know the best way to implement such a macro in ConTeXt, but I
want to make sure that the user-level behavior that you want is
properly
understood. Given the details in your question, one can easily lose the
forest for the trees (pun intended :-)
\unprotect
\installcorenamespace{localbox}
\unexpanded\def\newlocalbox#1%
  {\expandafter\let\expandafter#1\csname\??localbox\string#1\endcsname
   \ifx#1\relax
     \syst_aux_new_localbox#1%
   \fi}
\def\syst_aux_new_localbox#1%
  {\expandafter\newbox\csname\??localbox\string#1\endcsname
   \newlocalbox#1}
\protect
\starttext
\newlocalbox\BoxOne
\newlocalbox\BoxTwo
\setbox\BoxOne\hbox{Box One}
\setbox\BoxTwo\hbox{Box Two}
[\box\BoxTwo]
[\box\BoxOne]
\let\locbox\newlocalbox
\stoptext
-----------------------------------------------------------------
                                          Hans Hagen | PRAGMA ADE
              Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
       tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
_______________________________________________
dev-context mailing list
dev-context@ntg.nl
https://mailman.ntg.nl/mailman/listinfo/dev-context

Re: [dev-context] local allocation in ConTeXt

Sašo Živanović

Hans Hagen

Sašo Živanović

Hans Hagen

Sašo Živanović

Hans Hagen

tags

participants (2)