( there is a thread about this from 2014 but it went nowhere )

Symbolic differentiation might be interesting for my circuit
simulation engine. Is there a Forth package available
to handle this, or at least be helpful with nuts and bolts
when implementing something?

I'd like to avoid having to build a full Lisp or Prolog engine
first (unless these are completely hands-off / can be kept
invisible).

-marcel

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On 1/20/2024 5:17 AM, mhx wrote:

( there is a thread about this from 2014 but it went nowhere )

Symbolic differentiation might be interesting for my circuit
simulation engine. Is there a Forth package available
to handle this, or at least be helpful with nuts and bolts when
implementing something?

Perhaps the book Scientific Forth: A Modern Language for Scientific
Computing by Julian V. Noble would be a starting point?

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On Sat, 20 Jan 2024 14:17:37 mhx wrote:

( there is a thread about this from 2014 but it went nowhere )

Symbolic differentiation might be interesting for my circuit
simulation engine. Is there a Forth package available
to handle this, or at least be helpful with nuts and bolts
when implementing something?

I'd like to avoid having to build a full Lisp or Prolog engine
first (unless these are completely hands-off / can be kept
invisible).

John Wavrik ( https://math.ucsd.edu/~jwavrik/ ) has used
Forth for work in algebra. He is probably not active anymore,
but you might find some useful pointers on his pages
(also https://math.ucsd.edu/~jwavrik/pub/index.html ).

--
M.O.

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Hi,

By "Symbolic Differentiation", do you mean "Automatic Differentiation"?
If so you can see the Julia language packages for AD "Automatic Differentiation" based on:
- dual numbers
- complex numbers (for precision)

Bye

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Ahmed wrote:

By "Symbolic Differentiation", do you mean "Automatic Differentiation"?
If so you can see the Julia language packages for AD "Automatic Differentiation" based on:
- dual numbers
- complex numbers (for precision)

Whoa, thanks a lot for this pointer!

Actually, I was looking for Symbolic differentiation
( https://www.cs.utexas.edu/users/novak/asg-symdif.html ).

I didn't know there is a well-established difference between
'Symbolic' and 'Automatic' differentiation. A quite lucid
introduction to AS can be found on Wikipedia (https://en.wikipedia.org/wiki/Automatic_differentiation).

Instrumenting a compiler to find first order backward differences
alongside the 'normal' result, using dual numbers, is natural to
the Forth way of thinking and (appears) trivial to implement.
It might be much more fundamental to circuit simulation and discrete
control than I originally thought, and maybe even a breakthrough.

There might be a relation with past Forth experiments to implement
'reverse computation' or running programs backwards in time (website
of Forth UK?). I'll have to review that work.

Admittedly, I knew about Julia's secret AD weapon, but as it was never
properly explained what people meant with it, I had come to suspect that
it was just another hype. There's a JuliaCon in Eindhoven soon that
I probably should attend.

-marcel

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Marc Olschok wrote:

John Wavrik ( https://math.ucsd.edu/~jwavrik/ ) has used
Forth for work in algebra. He is probably not active anymore,
but you might find some useful pointers on his pages
(also https://math.ucsd.edu/~jwavrik/pub/index.html ).

Thank you. Not really what I was looking for, but I plan to read
the JOMA paper "Evolution of a Computer Application" (https://mathweb.ucsd.edu/~jwavrik/pub/23_Evolution.pdf),
eventually.

-marcel

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mhx@iae.nl (mhx) writes:

(https://en.wikipedia.org/wiki/Automatic_differentiation).

This is more concise and is where I first heard of the topic:

http://blog.sigfpe.com/2005/07/automatic-differentiation.html

It also points to a portal site, https://www.autodiff.org/

Sigfpe.com is a really cool site and I learned a lot there.

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Paul Rubin wrote:

mhx@iae.nl (mhx) writes:

(https://en.wikipedia.org/wiki/Automatic_differentiation).

This is more concise and is where I first heard of the topic:

http://blog.sigfpe.com/2005/07/automatic-differentiation.html

It also points to a portal site, https://www.autodiff.org/

Sigfpe.com is a really cool site and I learned a lot there.

Both references assume for granted that readers know why one
would want to symbolically differentiate a computational
procedure. I see that sigfpe's lost paper
(search on the Wayback machine for http://homepage.mac.com/sigfpe/paper.pdf) takes very good care of that and he probably didn't want to
repeat himself on his blog (such people exist :-)

-marcel

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mhx@iae.nl (mhx) writes:

Both references assume for granted that readers know why one
would want to symbolically differentiate a computational procedure. I
see that sigfpe's lost paper (search on the Wayback machine for http://homepage.mac.com/sigfpe/paper.pdf)
takes very good care of that and he probably didn't want to repeat
himself on his blog (such people exist :-)

A url from a blog comment is: http://web.archive.org/web/20120111180418/http://homepage.mac.com/sigfpe/paper.pdf

I believe that Sussman and Wisdom's book "Structure and Interpretation
of Classical Mechanics" (which presents a lot of classical mechanics
formulas as Scheme code) uses this method extensively. But I haven't
looked at the book much. Maybe someday. The book is online: see
"External links" at the end of

https://en.wikipedia.org/wiki/Structure_and_Interpretation_of_Classical_Mechanics

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