[erlang-questions] A simple multiply in the shell will kill the shell and its supervisor

Hynek Vychodil <>
Mon Apr 20 18:05:58 CEST 2009


It is not about number of C's. It should compute even
E=D*D*D*D*D*D*D*D*D*D*D*D*D*D,ok. but what I mean that your statements cause
print out each result. (Notice coma instead of dot.) Your terminal can be
slow for printing or there can be issue with erlang io subsystem. I have
tested that in Konsole (KDE on my Linux) I wait several seconds to print out
E but for examle in vim it will be crash reasonably. I don't know which
console werl and erl uses but I think there may be big difference.

On Mon, Apr 20, 2009 at 5:51 PM, Steve Kirsch <>wrote:

>  sure, it works with "fewer" C's in the computation. I already knew that.
>
> What do you meean a problem with io speed?
>
> I'm not trying to make this computation, I was only doing it for fun and
> was amazed I could crash the shell and its supervisor and nobody restarted
> anything doing something as simple as a multiply.
>
> Why does this happen and why does it happen only with erl and not werl on
> the same windows machine?
>
>  ------------------------------
> *From:* Hynek Vychodil [mailto:]
> *Sent:* Monday, April 20, 2009 6:15 AM
> *To:* Steve Kirsch
> *Cc:* 
> *Subject:* Re: [erlang-questions] A simple multiply in the shell will kill
> the shell and its supervisor
>
> Try do this:
> B=A*A*A*A*A,C=B*B*B*B*B*B*B*B*B*B*B,D=C*C*C*C*C*C*C*C*C*C*C,ok.
>
> There can be problem is with io speed.
>
> On Mon, Apr 20, 2009 at 9:32 AM, Steve Kirsch <>wrote:
>
>> This only seems to kill erlang's shell permanently using erl on Windows.
>> werl on the same machine works fine.
>>
>> Startup erl on windows.
>>
>> type in one line:
>> A=7480957234592457928345982345987234857923589723485728347598245927385724
>> 852984. B=A*A*A*A*A. C=B*B*B*B*B*B*B*B*B*B*B. D=C*C*C*C*C*C*C*C*C*C*C.
>>
>> then your erl will stop responding. It isn't in a loop and it isn't
>> using up cpu or crash dumping.
>>
>> It is just completely dead.
>>
>> I've tried this on two completely different PC's running windows XP Pro
>> with the same result. You do it on werl on the same machine, everything
>> is fine. Do it from erl, and it hangs.
>>
>> i am using R12B.
>>
>> inspection via a remote shell reveals that these processes have
>> disappeared from i() listing:
>> <0.26.0>              supervisor_bridge:user_sup/1           233
>> 81    0
>>                      gen_server:loop/6                        9
>>
>> <0.28.0>              user:server/2                          377
>> 600    0
>> user                  user:get_chars/7                        21
>>
>> <0.29.0>              erlang:apply/2                        4181
>> 4649    0
>>                      shell:get_command1/5                    16
>>
>> <0.35.0>              erlang:apply/2                        1597
>> 2550    0
>>                      shell:eval_loop/3                        6
>>
>>
>> why is this happening?
>> _______________________________________________
>> erlang-questions mailing list
>> 
>> http://www.erlang.org/mailman/listinfo/erlang-questions
>>
>
>
>
> --
> --Hynek (Pichi) Vychodil
>
> Analyze your data in minutes. Share your insights instantly. Thrill your
> boss.  Be a data hero!
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>



-- 
--Hynek (Pichi) Vychodil

Analyze your data in minutes. Share your insights instantly. Thrill your
boss.  Be a data hero!
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