5 Apr
2019
5 Apr
'19
9:56 a.m.
I suppose you could test each nybble for zero, then equate a 16-element LUT
on nybbles not zero?
--
Anders Nelson
+1 (517) 775-6129
www.erogear.com
On Fri, Apr 5, 2019 at 11:59 AM Kyle Owen via cctalk <cctalk at classiccmp.org>
wrote:
Just wondering if anyone has come up with a fast way
to count the number of
1s in a word on a PDP-8. The obvious way is looping 12 times, rotating the
word through the link or sign bit, incrementing a count based on the value
of the link or sign.
With a small lookup table, you can reduce the total number of loops by
counting multiple groups of bits at a time, but this of course comes with
the cost of using more memory. Any other suggestions?
Much appreciated,
Kyle