Re: DSL to C code generation with symbolic computations en route

On Mon, Apr 18, 2016 at 08:04:32PM +0200, Jerzy Karczmarczuk wrote:
> Dmitry Pavlov wants "adult" numerics in Racket, and he adds:
> 
> >- I need to take derivatives of equations that I wrote in my DSL,
> >symbolically, and have them converted to C too.
> 
> And then, people (Robby Findler and John Clements) mentioned Siskind. Good.
> 
> However, you should know that Jeffrey worked NOT on /symbolic/
> derivatives, but mainly on the "automatic differentiation" stuff;
> this is numeric, but fast and exact (in the sense: no differential
> quotient approximations). There is plenty of valuable papers written
> by Jeffrey and Barak Pearlmutter... (But some are quite difficult).

I am baffled how you can do differentiation numerically and get it exact.

> 
> If Dmitry is interested in numerical computations, and the "symbolic
> layer" would serve just to code some horrible "C", or similar, then
> please, the automatic differentiation /*is*/ the direction to
> follow.
> 
> Symbolic derivatives used then in numeric computations need a strong
> simplification package, otherwise the computations usually become
> very inefficient.

I understand needing a simplification pass -- naive symbolic 
differentiation tends to copy a lot of subexpressions.

-- hendrik

-- 
You received this message because you are subscribed to the Google Groups "Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/[email protected]
For more options, visit https://groups.google.com/d/optout.