Re: [NTG-context] distributed / parallel TeX?

17 Dec 2008


      Lars Huttar wrote:
...
On 12/16/2008 3:15 PM, luigi scarso wrote:
...
On Tue, Dec 16, 2008 at 9:08 AM, Taco Hoekwater mailto:taco@elvenkind.com> wrote:
Hi Lars,
Lars Huttar wrote:
....
...
So the question comes up, can TeX runs take advantage of
        parallelized or
        distributed processing?
No. For the most part, this is because of another requisite: for
    applications to make good use of threads, they have to deal with a
    problem that can be parallelized well. And generally speaking,
    typesetting  does not fall in this category. A seemingly small change
    on page 4 can easily affect each and every page right to the end
    of the document.
Also
3.11 Theory of page breaking
www.cs.utk.edu/~eijkhout/594-LaTeX/handouts/TeX%20LaTeX%20
http://www.cs.utk.edu/~eijkhout/594-LaTeX/handouts/TeX%20LaTeX%20*course*.pdf
Certainly that is a tough problem (particularly in regard to laying out
figures near the references to them). But again, if you can break down
the document into chunks that are fairly independent of each other (and
you almost always can for large texts), this problem seems no worse for
distributed processing than for sequential processing. For example, the
difficult part of laying out figures in Section 1 is confined to Section
1; it does not particularly interact with Section 2. References in
Section 2 to Section 1 figures are going to be relatively distant from
those figures regardless of page breaking decisions. Thus the difficult
problem of page breaking is reduced to the sequential-processing case...
still a hard problem, but one that can be attacked in chunks. Indeed,
the greater amount of CPU time per page that is made available through
distributed processing may mean that the algorithms can do a better job
of page breaking than through sequential processing.
you need to keep an eye on where tex spends its time on, and much is 
related to loading fonts, reading files, saving output, etc and with 
multiple threads one would have to coordinate that and make sure the 
time spent on it does not become larger overall

for instance, in your document making these large tables takes a while 
only because bTABLE is not that fast, so when at some point i can redo 
part of such mechanisms in lua we might gain way more runtime than by 
running distributed

Hans

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