Re: Is this a good use for "compile"

[Vítor De Araújo]

On 18/02/2018 18:56, Mark Carter wrote:
> New scheme user here.
>
> Suppose I'm writing a spreadsheet. The user inputs a formula for a cell.
>
> The plan is to use guile's peg parser to convert the formula into a 
> lambda expression, which I then compile in order to speed-up subsequent 
> processing.
>
> So, suppose I convert the user's formula to a list, which turns out to 
> be, for example: '(lambda (x) (+ x 13)) and compile it and save it in a 
> formula table:
>
> (hash-set! my-cell-formulae some-cell-ref (compile '(lambda (x) (+ x 13))))
>
> So I can I expect a speed-up by having done the compile, as opposed to 
> an eval?
>
> I assume the answer is "yes", but I wanted to check.

We can try this out:

scheme@(guile-user)> (use-modules (system base compile))
scheme@(guile-user)> (define exp '(lambda (n)
                                    (let loop ([i n] [total 0])
                                      (if (= i 0)
                                          total
                                        (loop (1- i) (+ i total))))))
scheme@(guile-user)> (define f1 (eval exp (interaction-environment)))
scheme@(guile-user)> (define f2 (compile exp #:env 
(interaction-environment)))
scheme@(guile-user)> ,time (f1 1000000)
$2 = 500000500000
;; 0.845240s real time, 0.895351s run time.  0.071494s spent in GC.
scheme@(guile-user)> ,time (f2 1000000)
$3 = 500000500000
;; 0.067317s real time, 0.067278s run time.  0.000000s spent in GC.

So the answer does seem to be "yes": the compiled procedure is much faster.

--
Vítor De Araújo
https://elmord.org/