\input gets slower after each \input

Hartmut Henkel hartmut_henkel at gmx.de
Tue Apr 27 19:41:44 CEST 2021

On Tue, 27 Apr 2021, barbara beeton wrote:
> On Tue, 27 Apr 2021, Phelype Oleinik wrote:
> > On 27/04/2021 12:34, barbara beeton wrote:
> > >
> > >  This has come up before, although with situations involving
> > >  different input file names, not the same name as in the present
> > >  test.  When a file access is completed (definitively closed),
> > >  ur-TeX would attempt to remove the name from the string pool. 
> > >  But if anything else had been added to the string pool, the name
> > >  was not removed, since the complications of garbage collection
> > >  outweighed the space saving.  I don't think that approach has
> > >  changed
> >
> > It doesn't seem to have been changed, because as Ulrike noted, the
> > example eventually explodes with a string pool overflow, and all it
> > does is to input the same file over and over again.
> >
> > However the access time for string memory is constant, since it is
> > just a pointer to a large array.  In fact, the sample takes roughly
> > the same time to run regardless if the file is
> > |abcdefghijklmnopqrstuvwxyz.tex| or just |a.tex|, which indicates
> > that it is not _how much_ string memory is used, but how many
> > strings are added to the pool.
> >
> > My questioning is if the space saved by reusing some chunks of the
> > string pool is worth the time taken to search through it...
> It certainly wasn't worth it when memory was at a premium; any space
> saved would have been (more than) consumed by the code necessary to
> accomplish it.
> > Speaking of which: if a string is reused when found in the pool, why
> > does the example runs out of string space?  Shouldn't it reuse
> > always the same string?
> It's been literally decades since the limitation was discovered at
> AMS, and even if the explanatory correspondence has survived, I no
> longer have access to it, and am not up to digging through the WEB
> code.

...not sure if this has to do with a problem tackled here, long long
ago: http://hhenkel.de/pdftex/patch3/avl-patch3.html

Best Regards, Hartmut

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