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Subject: Re: Question for Gerd: reduce rbb lookup tables

Author: Tim Foden

Date: 15:07:17 07/14/03

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On July 14, 2003 at 17:59:36, Sune Fischer wrote:

>On July 14, 2003 at 17:52:06, Gerd Isenberg wrote:
>
>Hi Gerd
>
>I was just wondering, you wouldn't happen to know an easy transformation for the
>diagonals, so that a table lookup for ths shift could be avoided?
>
>Somehow that shift bothers me, it should be possible to compute it on the fly I
>think.
>
>-S.

In GLC I don't do a shift for the diagonals, but fit the diagonally rotated
tables each into a 15 byte array, like this:

0000000X
000000XX
00000XXX
0000XXXX
000XXXXX
00XXXXXX
0XXXXXXX
XXXXXXXX
XXXXXXX0
XXXXXX00
XXXXX000
XXXX0000
XXX00000
XX000000
X0000000

So you just have to figure out which row to pick out of the table.

(In my newer prog, I pack the above into 8 bytes, still no shift, exercise left
to reader :))

Cheers, Tim.



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