Re: wip-ports-refactor

[Andy Wingo]

Hi,

On Sun 17 Apr 2016 12:44, address@hidden (Ludovic Courtès) writes:

> Andy Wingo <address@hidden> skribis:
>
>> I want to test four things.
>>
>>     ;; 1. How long a loop up to 10 million takes (baseline measurement).
>>     (let ((port (open-input-string "s"))) (do-times #e1e7 1))
>>
>>     ;; 2. A call to a simple Scheme function.
>>     (define (foo port) 42)
>>     (let ((port (open-input-string "s"))) (do-times #e1e7 (foo port)))
>>
>>     ;; 3. A call to a port subr.
>>     (let ((port (open-input-string "s"))) (do-times #e1e7 (port-line port)))
>>
>>     ;; 4. A call to a port subr that touches the buffer.
>>     (let ((port (open-input-string "s"))) (do-times #e1e7 (peek-char port)))
>>
>> The results:
>>
>>                       | baseline | foo    | port-line | peek-char
>>     ------------------+----------+--------+-----------+----------
>>     guile 2.0         | 0.269s   | 0.845s | 1.067s    | 1.280s
>>     guile master      | 0.058s   | 0.224s | 0.225s    | 0.433s
>>     wip-port-refactor | 0.058s   | 0.220s | 0.226s    | 0.375s
>
> Oh, nice!  (By “prohibitively slow” I was referring to 2.0.)
>
> For ‘peek-char’, isn’t there also the fact that string ports in 2.2 are
> UTF-8 by default, so we get the fast path, whereas in 2.0 there
> ‘%default-port-encoding’, which could be something else leading to the
> slow path?

I tried making sure the string port was a UTF-8 port but that made no
difference to the 2.0 peek-char times.  I suspect this is because I ran
it at the REPL, which had done a setlocale() already.  But perhaps
that's not the right explanation.

Andy