Re: Shrinking the C core

[Emanuel Berg]

Eli Zaretskii wrote:

> We are trying to make Lisp programs faster all the time,
> precisely because users do complain about annoying delays
> and slowness. Various optimizations in the byte-compiler and
> the whole native-compilation feature are parts of this
> effort

It's very fast with that, we should encourage more people do
use native-compilation.

>> If you take away nothing else from this conversation, at least get it
>> through your head that "more Lisp might make Emacs too slow" is a
>> deeply, *deeply* silly idea. It's 2023 and the only ways you can make
>> a user-facing program slow enough for response lag to be noticeable
>> are disk latency on spinning rust, network round-trips, or operations
>> with a superlinear big-O in critical paths.  Mere interpretive overhead
>> won't do it.
>
> We found this conclusion to be false in practice, at least in Emacs
> practice.

In theory Lisp can be as fast as any other language but in
practice it is not the case with Elisp and Emacs at least.

Here is a n experiment with stats how Emacs/Elisp compares
to SBCL/CL, for this particular one it shows that Elisp, even
natively compiled, is still +78875% slower than Common Lisp.

;;; -*- lexical-binding: t -*-
;;
;; this file:
;;   https://dataswamp.org/~incal/emacs-init/fib.el
;;
;; the CL:
;;   https://dataswamp.org/~incal/cl/fib.cl
;;
;; code from:
;;   elisp-benchmarks-1.14
;;
;; commands: [results]
;;   $ emacs -Q -batch -l fib.el                    [8.660 s]
;;   $ emacs -Q -batch -l fib.elc                   [3.386 s]
;;   $ emacs -Q -batch -l fib-54a44480-bad305eb.eln [3.159 s]
;;   $ sbcl -l fib.cl                               [0.004 s]
;;
;; (stats)
;;   plain  -> byte:     +156%
;;   plain  -> native:   +174%
;;   plain  -> sbcl:  +216400%
;;
;;   byte   -> native:     +7%
;;   byte   -> sbcl:   +84550%
;;
;;   native -> sbcl:   +78875%

(require 'cl-lib)

(defun compare-table (l)
  (cl-loop for (ni ti) in l
           with first = t
        do (setq first t)
           (cl-loop for (nj tj) in l
                 do (when first
                      (insert "\n")
                      (setq first nil))
                    (unless (string= ni nj)
                      (let ((imp (* (- (/ ti tj) 1.0) 100)))
                        (when (< 0 imp)
                          (insert
                            (format ";; %s -> %s: %+.0f%%\n" ni nj imp) )))))))

(defun stats ()
  (let ((p '("plain"  8.660))
        (b '("byte"   3.386))
        (n '("native" 3.159))
        (s '("sbcl"   0.004)) )
    (compare-table (list p b n s)) ))

(defun fib (reps num)
  (let ((z 0))
    (dotimes (_ reps)
      (let ((p1 1)
            (p2 1))
        (dotimes (_ (- num 2))
          (setf z (+ p1 p2)
                p2 p1
                p1 z))))
    z))

(let ((beg (float-time)))
  (fib 10000 1000)
  (message "%.3f s" (- (float-time) beg)) )

;; (shell-command "emacs -Q -batch -l \"~/.emacs.d/emacs-init/fib.el\"")
;; (shell-command "emacs -Q -batch -l \"~/.emacs.d/emacs-init/fib.elc\"")
;; (shell-command "emacs -Q -batch -l 
\"~/.emacs.d/eln-cache/30.0.50-3b889b4a/fib-54a44480-8bbda87b.eln\"")

(provide 'fib)

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https://dataswamp.org/~incal