The more I think about it the more I think that a full 17-bit LUT, as you
suggest, would be best. Only an experiment will tell :-)

On Thu, Oct 13, 2016 at 8:34 PM, Michal Dobrogost <
michal.dobrog...@gmail.com> wrote:

> A 17-bit lookup table for a 17x1024 sized Y would require 16 MB. The 4-bit
> version is 10kb and would fit into the L1 cache. I believe the L1 vs RAM
> access times are 1-to-60 or so (http://www.7-cpu.com/cpu/Haswell.html).
>
> Of course, maybe we use few enough Xs at any given time that the relevant
> entries of a 17-bit LUT would be hot anyway.
>
> On Thu, Oct 13, 2016 at 8:04 PM, Raul Miller <rauldmil...@gmail.com>
> wrote:
>
>> Simplest "high performance" version of that would be to pre-compute each
>> of
>> the possible answers for each possible X.
>>
>> --
>> Raul
>>
>>
>> On Thu, Oct 13, 2016 at 9:33 PM, Michal Dobrogost <
>> michal.dobrog...@gmail.com> wrote:
>>
>> > Yes, you can rewrite (+./@:*.) as (+./ . *.).
>> >
>> > Hehe, in terms of peculiar ways and unknown reasons, I invite you to
>> think
>> > about how you might go about implementing a high-performance version of
>> > this operation where X and Y are restricted to boolean elements, Y is
>> > static and X dynamically changes.
>> >
>> > On Thu, Oct 13, 2016 at 10:32 AM, Erling Hellenäs <
>> > erl...@erlinghellenas.se>
>> > wrote:
>> >
>> > > It is this operation +./ . *. we rewrite in peculiar ways for unknown
>> > > reasons?
>> > >
>> > > [ x=: 1 0 1 1 0
>> > >
>> > > 1 0 1 1 0
>> > >
>> > > [ y=: 5 6 $1 0 0 0 0 0 0 1 0 1 1 0 0 1 0 0 0 1 0 0 0 0 1 1 0 1 1 1 0 1
>> > >
>> > > 1 0 0 0 0 0
>> > >
>> > > 0 1 0 1 1 0
>> > >
>> > > 0 1 0 0 0 1
>> > >
>> > > 0 0 0 0 1 1
>> > >
>> > > 0 1 1 1 0 1
>> > >
>> > > x +./ . *. y
>> > >
>> > > 1 1 0 0 1 1
>> > >
>> > >
>> > > /Erling
>> > >
>> > >
>> > >
>> > > ------------------------------------------------------------
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>
>
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