Re: guile-2.9.1 impressions

[Linas Vepstas <linasvepstas@gmail.com>]

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Andy,

I want to temporarily, maybe permanently retract my last email. I found a
bug(let) in the intialization of my unit test that appears to maybe account
for all observed crashes, maybe. I'm re-verifying on multiple machines but
this will take 24-48 hours.  Basically, it looks like guile-2.9.2 is crash
free (for the last 6 hours) on one os/compiler/glibc combination, I have to
cross-check on another.

--linas

On Sun, May 26, 2019 at 8:40 AM Linas Vepstas <linasvepstas@gmail.com>
wrote:

> Hi Andy,
>
> Thanks!  I just tried out the master branch of guile in git (the one
> tagged v2.9.2). It now passes all of my unit tests.  So that's good! ...
> More or less -- there's still some infrequent multi-threading bug(s).  Let
> me describe.
>
> My unit test just transitions C->guile->C and returns, in rapid
> succession, in 20 threads. So, in pseudocode:
>
> SCM do_stuff(SCM a, SCM b) {
>       scm_to_utf8_string(a);
>       scm_to_int(b);
>      ... minor stuff... return scm_from_int(...);
> }
> scm_c_define_gsubr("do-things",2,0,0, do_stuff);
>
> void thing_doer(int thread_id) {
>      for (i=0; i=15000; i++)
>            char str[100];
>            sprintf(str, "(do-things foo %d)", i);
>            scm_c_catch(scm_eval_string,  str);
> }
>
> main () {
>       for (int i=1; i<15; i++)   // start 15 threads
>             std::thread(&thing_doer, i);
> }
>
> I'm guessing the above code spends maybe 90% of its time bouncing between
> guile and C. The string "(do-things foo 42)" changes each time in the loop,
> so, not sure how the compile vs. interpret tradeoff is done.  Either way,
> its relatively trivial. Likewise, the do_stuff() C routine is fairly thin;
> after decoding it's args, it doesn't do all that much (sub-microsecond of
> computing).  Based on old, old measurements, scm_eval_string really is the
> primary CPU consumer, in the 20-microseconds range. Launching 15 threads
> means that this thing is racing as fast as it can.
>
> Anyway, with guile-2.9.2, the above crashes after about 10-15 minutes,
> either with memory corruption, or with segfault.  I worried, so I retested
> with guile-2.2.4 ... which also crashes, but much much less frequently:
> seven times in 44 hours wall-clock time (so once ever 6 hours).  Which is
> still more than desired, but...OK.
>
> So where's the crash? No clue. Could be my code, could be guile. Since
> there's a big difference between guile-2.2 and guile-2.9, I'm ready to
> blame guile. I did try to run it with `valgrind --tool helgrind` and got an
> ocean of complaints about guile GC, which are probably harmless. I haven't
> tried to dig deeper yet.
>
> -- Linas
>
>
> On Thu, May 23, 2019 at 2:28 PM Andy Wingo <wingo@pobox.com> wrote:
>
>> Hi!
>>
>> On Thu 06 Dec 2018 06:21, Linas Vepstas <linasvepstas@gmail.com> writes:
>>
>> > After sending the email below, I scanned the guile-devel archives,
>> > and I see Thomas Morley talking about Lilypond performance.
>> > The example program he offers up caught my eye: nested deep
>> > in a loop is this:
>> >
>> > (eval-string "'(a b c)")
>>
>> In this case I believe Guile 2.9 / 3 should be significantly faster than
>> 2.2, because `eval' is compiled to native code rather than bytecode.  My
>> measurements showed it to be on par with the hand-optimized C
>> implementation from 1.8 and before.  Depends of course on how much the
>> expander is part of your workload, there are differences relative to
>> Guile 1.8.  Anyway, thanks for the note and I just wanted to mention
>> this point.
>>
>> Regarding Scheme -> C++ transitions, there is the possibility that this
>> too could be much faster with Guile 2.9.x given that these calls are now
>> JIT-compiled instead of interpreted.  We'll have to see.
>>
>> Cheers,
>>
>> Andy
>>
>
>
> --
> cassette tapes - analog TV - film cameras - you
>


-- 
cassette tapes - analog TV - film cameras - you

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