Re: funcall consing

[LdBeth <andpuke@foxmail.com>]

>>>>> In <87ee5tm422.fsf@logand.com> 
>>>>>	Tomas Hlavaty <tom@logand.com> wrote:
Tomas> Hi,

Tomas> in order to optimize some elisp code, I am trying to understand where my
Tomas> consing comes from.  So far it looks like that my assumption about the
Tomas> cause of consing are wrong and that the cause of consing is funcall.  Is
Tomas> that plausible?  I am seeing similar results like this (lexical-binding,
Tomas> also byte compiled):

Tomas> (benchmark-run 10 (dotimes (i 100000) (1+ i)))
Tomas> ;;(2.720941123 40 1.7525918699999998)
Tomas> (let ((x (lambda (i) (1+ i)))) (benchmark-run 10 (dotimes (i 100000) (funcall x i))))
Tomas> ;;(4.9373091140000005 80 3.4835688719999958)

Tomas> i.e. funcall conses a lot and introduces cca double performance penalty.

Tomas> Is that right or am I doing something wrong?

Tomas> Would it be possible to improve that?

Try this:

```
(defun bar () (benchmark-run 10 (dotimes (i 100000) (1+ i))))
(defun foo () (let ((x (lambda (i) (1+ i))))
  (benchmark-run 10 (dotimes (i 100000) (funcall x i)))))

(byte-compile 'foo)
(byte-compile 'bar)

(foo)
(0.054734 0 0.0)
(bar)
(0.019939000000000002 0 0.0)
```