Speed or space

Date	2022-02-09 01:32 +1100
Newsgroups	comp.lang.postscript
From	David Newall <davidn@davidnewall.com>
Subject	Speed or space
Message-ID	<62027f03$1@news.ausics.net> (permalink)
Organization	Ausics - https://www.ausics.net

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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.

                       ---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?

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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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