[erlang-questions] how much time required to pass messages.

Mark Wagner <>
Thu Apr 2 03:53:36 CEST 2009


Because the timer resolution is too small.  What does
tokenring:tokenring(120000,1). produce?

-- 
Mark

2009/3/30 Vikrant <>:
> even if timer resolution is the reason why we don't see the change in time,
> question remains same. why the change in time scales with M(number of
> messages) and NOT with N (number of processes + number of messages)!
>
> 2009/3/29 Carsten Schultz <>
>>
>> Vikrant schrieb:
>> >
>> > 26> tokenring:tokenring(10000,1).
>> > Time required to pass message 10000 times=3.00000 (4.40000) microsecond
>> > .ok
>> > 27> tokenring:tokenring(20000,1).
>> > Time required to pass message 20000 times=3.00000 (4.65000) microsecond
>> > .ok
>> > 28> tokenring:tokenring(30000,1).
>> > Time required to pass message 30000 times=3.33333 (4.63333) microsecond
>> > .ok
>> >
>> > (time in bracket is system time and time outside bracket is user time in
>> > microseconds.)
>> >
>> > This is surprising to me! I expected that time required to pass token
>> > along N processes should be proportional to N!
>>
>> My guess here is that the resultion of the timer is 1/3.  So your
>> results are 9, 9, 10.  Considering that these are rounded and that your
>> function will have a constant term, these numbers are just to small to
>> allow you to deduce much about your runtime function.  Change the second
>> parameter into, say, 1000000 in all cases and see what happens.
>>
>> --
>> Carsten Schultz (2:38, 33:47)
>> http://carsten.codimi.de/
>> PGP/GPG key on the pgp.net key servers,
>> fingerprint on my home page.
>
>
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