Re: CC Mode -> Tree sitter challenge

[Theodor Thornhill <theo@thornhill.no>]

Hi Eli,

[...]

>> - TypeScript (left out, as it is in tree-sitter branch already)
>
> Thanks.

My pleasure.

>> 2. I've focused mostly on indentation and font locking.  Indentation is
>> using xdisp code style and the gnu style in general.
>
> We should ideally support all the indentation styles supported by CC
> Mode.
>

Yes, I'll try to be as comprehensive as possible.

>> When scrolling through xdisp with this variant of C support it is
>> noticeably faster on my system.  However, I'd like some guidance on how
>> to provide some benchmarks to prove my guess.
>
> We usually use something like the below:

Thanks, I used them, see results below.

> The instructions are: visit xdisp.c and immediately invoke one of
> these two functions; then record the time it took to scroll through
> the entire file.  Compare to CC Mode.
>
> I think we also want to see the above modified to make some change to
> the buffer once in a while.  For example, once in 100 lines insert a
> quote ", or a /* followed by */ after several lines, and see how that
> affects the scroll times with both modes.
>
>> Loading said file and immediately going to EOB is instant, but in CC
>> Mode takes a little less than a second.
>
> Timing this with benchmark-run and presenting the numbers is also
> interesting.

So this is the code with results thus far.  It is immediately apparent
how much faster this is, IMO.  Every test is run from a fresh `emacs
-Q`.  I just eval the files, enable the modes and run the tests.

What do you think?  Is there anything clearly wrong with the benchmarks?
In many of the cases tree-sitter is an order of magnitude faster.

```
(defun scroll-up-benchmark ()
  (interactive)
  (let ((oldgc gcs-done)
        (oldtime (float-time)))
    (condition-case nil (while t (scroll-up) (redisplay))
      (error (message "GCs: %d Elapsed time: %f seconds"
                      (- gcs-done oldgc) (- (float-time) oldtime))))))

(defun scroll-up-by-40-benchmark ()
  (interactive)
  (let ((oldgc gcs-done)
        (oldtime (float-time)))
    (condition-case nil (while t (scroll-up 40) (redisplay))
      (error (message "GCs: %d Elapsed time: %f seconds"
                      (- gcs-done oldgc) (- (float-time) oldtime))))))

(defun scroll-up-insert-quote-benchmark ()
  (interactive)
  (let ((oldgc gcs-done)
        (oldtime (float-time)))
    (condition-case nil
        (while t
          (scroll-up 50)
          (when (zerop (mod (1- (line-number-at-pos)) 100))
            (insert "\""))
          (redisplay))
      (error (message "GCs: %d Elapsed time: %f seconds"
                      (- gcs-done oldgc) (- (float-time) oldtime))))))


(defun xdisp-eob-benchmark ()
  (benchmark-run 100
    (progn
      (with-current-buffer (find-file "~/src/emacs/src/xdisp.c")
	(end-of-buffer))
      (kill-buffer "xdisp.c"))))

;; C-MODE
;; scroll-up-benchmark
;; 1: GCs: 402 Elapsed time: 17.499269 seconds
;; 2: GCs: 415 Elapsed time: 17.789382 seconds

;; scroll-up-by-40-benchmark
;; 1: GCs: 420 Elapsed time: 19.183639 seconds
;; 2: GCs: 420 Elapsed time: 19.377480 seconds

;; xdisp-eob-benchmark 100
;; 1: (40.992420494 1708 16.708356162)
;; 2: (40.630712261 1711 16.361947911999998)

;; xdisp-eob-benchmark 1
;; 1: (0.482883063 21 0.19676500600000002)
;; 2: (0.478595514 21 0.19573110300000002)

;; scroll-up-insert-quote-benchmark
;; 1: GCs: 558 Elapsed time: 41.747822 seconds
;; 2: GCs: 557 Elapsed time: 41.976805 seconds


;; C-TS-MODE
;; scroll-up-benchmark
;; 1: GCs: 21 Elapsed time: 6.997570 seconds
;; 2: GCs: 27 Elapsed time: 7.239952 seconds

;; scroll-up-by-40-benchmark
;; 1: GCs: 30 Elapsed time: 8.869021 seconds
;; 2: GCs: 29 Elapsed time: 9.076617 seconds

;; xdisp-eob-benchmark 100
;; 1: (15.083917789 20 1.1350005760000001)
;; 2: (15.213992551999999 21 1.121564519)

;; xdisp-eob-benchmark 1
;; 1: (0.19189711499999998 1 0.011011572999999997)
;; 2: (0.185749092 1 0.011173242)

;; scroll-up-insert-quote-benchmark
;; 1: GCs: 29 Elapsed time: 15.450495 seconds
;; 2: GCs: 29 Elapsed time: 12.168593 seconds
```

Theo