Re: mapfiles and pdftex

[Hans Hagen <pragma@wxs.nl>]

At 08:53 AM 2/12/2003 +0100, you wrote:
>Hartmut Henkel <hartmut_henkel@gmx.de> writes:
>
>Hello Hartmut,
>
> > Don't know what is slow for your PC.
>
>at least two seconds just for the map file.
>
> > I'm just looking into pdftex mapfile.c, about 2and there is in line 142 a
> > for-loop for checking duplicate mapfile entries (tfm). This runs
> > some 3000*0.5*3000 times for parsing your mapfile lines, always
> > checking for some strcmp() == 0. You can speed this up if you put a
> > line "if (*(e->tfm_name) != *buf) continue;"
>
>But this also looks like O(n^2) to me. With 3000*3000 is some 9 million!
>
> > So there might be some corner for improvement. Using strcmp() the
> > reverse way seems not to speed up things; how to write a more
> > sophisticated inequality-checker?
>
>Heiko stated that he used a hash table for this. This will speed up
>things dramatically.

but if i remember right he only looked at the first 8 chars (assuming 
berry) which is not that useful for texnansi-* files -)

the best way (imo) is to let later entries overload previous ones, so not 
much checking is needed at all;

>But this is getting slightly off topic, isn't it?

future versions of pdftex will solve this problem;

another thing is reading map files after the first page is shiped out; that 
would permit us to postpone map file loading and speed things up a bit; 
currently, if you want to use a specific font on page 328 you must make 
sure that the associated map file is loaded before page 1 is finished!

Hans


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