[reSIProcate] Exception encountered when using reSIProcate in a multi-threaded program

[Scott Godin]

"We are using the time in ms xor thread id as the seed value. This just
isn't 
going to cut it."
 
I'm not sure I understand the issue with the current scheme - as long as you
seed for each thread.  The thread id is used in the seed - so it should be
unique - even if 2 threads seed in the same second.
 
Note:  Resip 0.9 does not contain the changes I made in the SVN head in
order to ensure every windows thread is seeded correctly.  Resip 0.9 relies
on the application calling random::init() if it is not using ThreadIf for
threading.
 
Scott
 
  _____  

From: Fischl jason [mailto:jason.fischl at gmail.com] 
Sent: Monday, July 18, 2005 9:25 PM
To: Alan Hawrylyshen
Cc: resiprocate-devel at list.sipfoundry.org; Andy Agarwal
Subject: Re: [reSIProcate] Exception encountered when using reSIProcate in a
multi-threaded program
 
I think I got it. In win32, each thread needs to seed the rng. We are 
using the time in ms xor thread id as the seed value. This just isn't 
going to cut it. I'm going to try changing it to use GetTickCount 
instead of Timer::getTimeMs. Also, going to change some other things 
in the seed value. 
More specifically: 
Data buffer; 
DataStream strm(buffer); 
strm << GetTickCount() << ":" 
strm << GetCurrentProcessId() << ":"; 
strm << GetCurrentThreadId(); 
strm.flush(); 
unsigned int seed = buffer.hash(); 




On 7/18/05, Alan Hawrylyshen <alan at jasomi.com> wrote: 
> 
> On Jul 18, 2005, at 17.38, Fischl jason wrote: 
> 
> > 
> > You may also need to put debug in Random::getRandomHex. Possibly we're 
> > getting nailed on some win32 thread safety issue with getRandom. Focus 
> > your effort there. 
> > 
> 
> 
> It just dawned on me that this behavior can arise when (if) the 
> random number generator is initialized repeatedly. 
> If the seed it timebased and your call resolution is smaller than the 
> clock resolution, you will get duplicates. 
> 
> Alan 
> 
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> resiprocate-devel at list.sipfoundry.org 
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> 
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