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Groups > comp.lang.postscript > #3750

Re: Speed or space

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On Wed, 9 Feb 2022 01:32:35 +1100
David Newall <davidn@davidnewall.com> wrote:

> Still working on utf8show and have classic space vs. time tradeoff.
> 
> I can store the UnicodeEncoding map in a Dictionary, which is
> blindingly fast, or in a sparse array, which is more compact but
> slower to access. Every glyph painted needs a lookup in the map.

I don't know what a sparse array is in this context. Is it like the
input array to unicodefont? In that case maybe it could be optimized,
by, idk, putting code points in entries 0, 2, 4, 6, ... to speed up
lookup, and the corresponding arrays with glyph names (or just the main
glyph name) in entries 1, 3, 5, 7, ..., or something like that.
> 
>                        ---Bytes Used-- --Savings-- -Time(ms)-- S:D ms
> Map Source                Dict Sparse   Bytes  %  Dict Sparse  Ratio
> AdobeGlyphList(1)      222472  180798   41686 19%  161   2968  18.45
> FreeSerif.gn2(2)       442320  356006   86314 20%  604   2856   4.73
> UnifontMedium.gn2(3)  3357832 2173806 1184026 35%  156    949   6.08
> 
> (1) AdobeGlyphList from ghostscript v9.50 on Ubuntu 20.04.3.
> 
> (2) Generated by fontforge from FreeSerif.sfd extracted from
>      freefont-src-20120503.tar.gz from ftp.gnu.org/gnu/freefont.
> 
> (3) Generated by fontforge from unifont-14.0.01.ttf extracted
>      from unifont-14.0.01.tar.gz from ftp.gnu.org/gnu/unifont/.
> 
> Tests were performed using Ghostscript 9.5 on Ubuntu 20.04.3 with
> Intel(R) Core(TM) i7-1165G7 @ 2.80GHz.  Glyphs for UNICODE values 0
> through 150,000 were retrieved from each map five times.
> 
> I don't know why accessing the sparse Adobe map is so much slower than
> the other two.  Average retrieval time is under 4ns; for UnifontMedium
> it's under 1.3ns.
> 
> I'm going to implement it one way only.  Which should it be?

Contrary to John's opinion, I don't think space matters much,
especially if it's only 3 MB. So I'd choose speed. But then, I don't
know anything about Postscript printers or other low capacity devices.

C.

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Thread

Speed or space David Newall <davidn@davidnewall.com> - 2022-02-09 01:32 +1100
  Re: Speed or space John Reiser <vendor@BitWagon.com> - 2022-02-09 09:59 -0800
  Re: Speed or space Carlos <carlos@cvkm.cz> - 2022-02-10 15:28 +0100
    Re: Speed or space David Newall <davidn@davidnewall.com> - 2022-02-16 14:29 +1100

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