bugGuile - Bugs: bug #30901, High runtime variance

 
 

bug #30901: High runtime variance

Submitter:  Andy Wingo <wingo>
Submitted:  Sun 29 Aug 2010 07:49:05 PM UTC
   
 
Category:  None Severity:  3 - Normal
Item Group:  None Status:  Works For Me
Privacy:  Public Assigned to:  None
Open/Closed:  Closed
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Fri 17 Jun 2011 06:07:38 PM UTC, comment #2: 

I too no longer see the high runtime variance, but that is with a different machine, os, and newer guile.  Pleasantly the same test runs in 1.25 seconds here :)

Anyway, your suggestion sounds good Stefan.  I will close as works-for-me.

Andy Wingo <wingo>
Group administrator
Thu 09 Jun 2011 04:00:54 PM UTC, comment #1: 

I could see this before as well (pre 2.0)

Upgrading the OS and pulling guile-2.0 head revealed that this was no longer an issue. I noted that (times) now returns ns.

The question is if this BUG now can be closed.

/Stefan

Stefan Israelsson Tampe <tampe>
Group Member
Sun 29 Aug 2010 07:49:05 PM UTC, original submission:  

Luca Saiu made an interesting test case:

  http://thread.gmane.org/gmane.lisp.guile.bugs/4538

It runs Guile ten times, each time running a recursive fibonacci function three times in a row. Within each Guile run, the three fibonacci runs do take the same amount of time, but times vary considerably between the various Guile runs.

For example, here the run results in the following:


$ rm -rf ~/.cache/guile/; for i in `seq 10`; do

> guile --autocompile q.scm; echo; done

;;; note: autocompilation is enabled, set GUILE_AUTO_COMPILE=0
;;;       or pass the --no-autocompile argument to disable.
;;; compiling q.scm
;;; compiled /home/wingo/.cache/guile/ccache/2.0-0.R-LE-8/tmp/q.scm.go
(begin (fibo n)) returned 9227465 in 3.13 seconds.
(begin (fibo n)) returned 9227465 in 3.13 seconds.
(begin (fibo n)) returned 9227465 in 3.13 seconds.

(begin (fibo n)) returned 9227465 in 3.04 seconds.
(begin (fibo n)) returned 9227465 in 3.04 seconds.
(begin (fibo n)) returned 9227465 in 3.04 seconds.

(begin (fibo n)) returned 9227465 in 3.24 seconds.
(begin (fibo n)) returned 9227465 in 3.24 seconds.
(begin (fibo n)) returned 9227465 in 3.25 seconds.

(begin (fibo n)) returned 9227465 in 3.13 seconds.
(begin (fibo n)) returned 9227465 in 3.15 seconds.
(begin (fibo n)) returned 9227465 in 3.14 seconds.

(begin (fibo n)) returned 9227465 in 3.25 seconds.
(begin (fibo n)) returned 9227465 in 3.24 seconds.
(begin (fibo n)) returned 9227465 in 3.25 seconds.

(begin (fibo n)) returned 9227465 in 3.65 seconds.
(begin (fibo n)) returned 9227465 in 3.65 seconds.
(begin (fibo n)) returned 9227465 in 3.63 seconds.

(begin (fibo n)) returned 9227465 in 3.36 seconds.
(begin (fibo n)) returned 9227465 in 3.37 seconds.
(begin (fibo n)) returned 9227465 in 3.38 seconds.

(begin (fibo n)) returned 9227465 in 3.33 seconds.
(begin (fibo n)) returned 9227465 in 3.35 seconds.
(begin (fibo n)) returned 9227465 in 3.33 seconds.

(begin (fibo n)) returned 9227465 in 3.6 seconds.
(begin (fibo n)) returned 9227465 in 3.6 seconds.
(begin (fibo n)) returned 9227465 in 3.61 seconds.

(begin (fibo n)) returned 9227465 in 3.4 seconds.
(begin (fibo n)) returned 9227465 in 3.41 seconds.
(begin (fibo n)) returned 9227465 in 3.4 seconds.


In that thread I mentioned that I suspected it was GC, but that doesn't sound likely, as this benchmark doesn't cons. So perhaps it is indeed alignment.

The next step here is to run Guile under oprofile or perf, detecting such things as cache misses.

Andy Wingo <wingo>
Group administrator

 

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    2011-06-17 wingo StatusNone Works For Me
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