[Jprogramming] Gustafson's Unums Revisited
roger stokes
rogerstokes811 at gmail.com
Wed Aug 17 15:47:15 UTC 2016
Typo in my last: "gives 0.5j0" should be "Gives "_0.5j0"
Sorry.
On Wed, Aug 17, 2016 at 4:43 PM, roger stokes <rogerstokes811 at gmail.com>
wrote:
> Skip,
>
> you wrote "Shouldn't converting _0.25 to a SORN, then back to a
> J number produce _0j0.5, NOT _0.5? "
> I believe the result given is correct, because _0.25 is in the
> interval (_0.5 0) in 4-bit precision.
>
> A =: SFJN _0.25
>
>
> (> A) # UNUMS
> +------+
> ¦_1r2 0¦
> +------+
>
> Rendering this as a complex number, with real for lower bound _1r2
> and imaginary for upper bound 0 gives 0.5j0 which is presented by J
> as a real number because imag = 0
>
> ] B =: JNFS A
> _0.5
> datatype B
> complex
> B = _0.5j0
> 1
>
>
> I rest my case.
>
> These conversions are not yet finished nor documented, in fact the whole
> thing is pretty rough. On that subject, let me mention that until I get it
> cleaned up, users should avoid one-character lower case variables, because
> of my sloppy style of doing global assigns to what should be local.
>
> I thought it would be best to use rationals for the values, rather than
> reals,
> so that the computations for the lookup tables would be exact.
>
> Regards
>
> On Wed, Aug 17, 2016 at 3:02 PM, Skip Cave <skip at caveconsulting.com>
> wrote:
>
>> Playing with 4-bit unums (compact SORNS), I thought I would see how the
>> J-to-SORN & SORN-to-J conversions worked:
>>
>> JNFS SFJN _3
>>
>> __j_2
>>
>> JNFS SFJN _2.5
>>
>> __j_2
>>
>> JNFS SFJN _2
>>
>> _2
>>
>> JNFS SFJN _1.5
>>
>> _2j_1
>>
>> JNFS SFJN _1
>>
>> _1
>>
>> JNFS SFJN _0.5
>>
>> _1r2
>>
>> JNFS SFJN _0.25
>>
>> _0.5 NB. ??
>>
>> JNFS SFJN _0
>>
>> 0
>>
>> JNFS SFJN 0
>>
>> 0
>>
>> JNFS SFJN 0.25
>>
>> 0j0.5
>>
>> JNFS SFJN 0.5
>>
>> 1r2
>>
>> JNFS SFJN 0.75
>>
>> 0.5j1
>>
>> JNFS SFJN 1
>>
>> 1
>>
>> JNFS SFJN 1.5
>>
>> 1j2
>>
>> JNFS SFJN 1.75
>>
>> 1j2
>>
>> JNFS SFJN 2
>>
>> 2
>>
>> JNFS SFJN 2.5
>>
>> 2j_
>>
>> JNFS SFJN 3
>>
>> 2j_
>>
>> JNFS SFJN _
>>
>> 2j_
>>
>> JNFS SFJN __
>>
>> __
>>
>>
>> This would have been easier if JNFS and SFJN could handle vectors. In any
>> case, everything looked good, once I understood how Roger was representing
>> intervals in J as complex numbers, EXCEPT converting _0.25. Shouldn't
>> converting _0.25 to a SORN, then back to a J number produce _0j0.5, NOT
>> _0.5?
>>
>>
>> Skip
>>
>>
>> Skip Cave
>> Cave Consulting LLC
>>
>> On Wed, Aug 17, 2016 at 7:21 AM, Skip Cave <skip at caveconsulting.com>
>> wrote:
>>
>> > Is there a way for the unum lab to discover where it was started from,
>> and
>> > then set the working directory to that location, rather than having the
>> > user have to set the directory?
>> >
>> > Skip
>> >
>> > Skip Cave
>> > Cave Consulting LLC
>> >
>> > On Wed, Aug 17, 2016 at 6:47 AM, roger stokes <rogerstokes811 at gmail.com
>> >
>> > wrote:
>> >
>> >> Dear All,
>> >>
>> >> Please accept my apologies for wasting your time, and my thanks
>> >> for your patience, persistence and help.
>> >>
>> >> Skip, Raul, Vijay, you are quite right about 1 !: 44 .
>> >> Instead of cd .... I should have said
>> >>
>> >> 1 !: 44 'yourdirectory' NB. full pathname is recommended
>> >>
>> >>
>> >> Vijay, I made a correction following your mention of
>> general/misc/fndef .
>> >> This file should not be needed.
>> >>
>> >>
>> >> Bob, thanks for the suggestion - it's a good way to get the lab
>> started
>> >> but there is still the need to find the other scripts. I will ponder
>> this
>> >> and see if there is a better way than as it is.
>> >>
>> >> Bill, thanks for the information about jconsole - I didn't know this
>> >> and am very glad you mentioned it.
>> >>
>> >> I have now uploaded a corrected version to
>> www.learningj.com/unumslab.zip
>> >> .
>> >> However, I hope, I believe, that the VERSION YOU ALREADY HAVE should
>> run
>> >> OK by doing this:
>> >>
>> >> 1 !: 44 'yourdirectory'
>> >>
>> >> first =: {. NB. workaround for Vijay's issues
>> >> snd =: 1 & {
>> >>
>> >> load 'labs/labs'
>> >>
>> >> lab_jlab_ 'unums.ijt'
>> >>
>> >>
>> >> Thanks again, everyone
>> >>
>> >> On Wed, Aug 17, 2016 at 4:12 AM, bill lam <bbill.lam at gmail.com> wrote:
>> >>
>> >> > In the readme, it said
>> >> > ... jconsole doesn't support labs
>> >> >
>> >> > This is incorrect. One can run labs on jconsole
>> >> > and type labrun_jlab_ '' (and up arrow to recall)
>> >> > to advance.
>> >> >
>> >> > Вт, 16 авг 2016, roger stokes написал(а):
>> >> > > Dear All,
>> >> > >
>> >> > > I've heard it said that you don't understand a subject
>> >> > > unless you can explain it to a computer. With that in mind
>> >> > > I've attempted a software implementation of Gustafson's Unums 2.0
>> >> > >
>> >> > > ( http://www.johngustafson.net/presentations/Unums2.0.pdf ).
>> >> > >
>> >> > > If anyone is interested, there is a demo available in the
>> >> > > form of a J lab. To run the lab
>> >> > >
>> >> > > Download www.learningj.com/unumslab.zip
>> >> > >
>> >> > > Unzip into any convenient directory
>> >> > >
>> >> > > Follow directions in the readme file
>> >> > >
>> >> > > Comments and criticisms appreciated.
>> >> > >
>> >> > > Regards
>> >> > > ------------------------------------------------------------
>> >> ----------
>> >> > > For information about J forums see http://www.jsoftware.com/forum
>> >> s.htm
>> >> >
>> >> > --
>> >> > regards,
>> >> > ====================================================
>> >> > GPG key 1024D/4434BAB3 2008-08-24
>> >> > gpg --keyserver subkeys.pgp.net --recv-keys 4434BAB3
>> >> > gpg --keyserver subkeys.pgp.net --armor --export 4434BAB3
>> >> > ------------------------------------------------------------
>> ----------
>> >> > For information about J forums see http://www.jsoftware.com/forum
>> s.htm
>> >> >
>> >> ----------------------------------------------------------------------
>> >> For information about J forums see http://www.jsoftware.com/forums.htm
>> >>
>> >
>> >
>> ----------------------------------------------------------------------
>> For information about J forums see http://www.jsoftware.com/forums.htm
>>
>
>
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