Re: [Boost-users] boost::random issue with icc on Windows

From: John Maddock (john_at_[hidden])
Date: 2007-12-12 07:59:56

Geoff Wedig wrote:
> Hello,
>
> We are experiencing a problem with boost::random using icc on Windows
> under optimization.  If we compile with the -O1 option, we get correct
> behavior.  Compiling with -O2 or no -O option gives us a string of
> zeros.
>
> We have compiled a small test case which shows this problem:

> To date, I've done a lot of hunting trying different compiler options
> to attack this problem.  The compiler option which seems to have the
> most consistent effect, in that adding it makes the program work,
> whereas removing it makes it not is -Qunroll0.
>
> I am guessing something in the optimization is causing the generator
> not to initialize properly, but I do not, at present, know how to
> solve it.
>
> Has anyone else seen this, or have any ideas what might be going
> wrong?

Sorry, no.  What I normally do in cases like this is a bit of "comparitive 
debugging": start up two instances of Visual Studio, and debug both, one 
with optimisation on, one with it off, and see what the difference is.

It's always possible that there's an un-initialised variable bug lurking 
somewhere of course, but I would have expected that to have shown up by now 
if that was the case.

BTW, I tried your code with reasonably up to date versions of Intel 9.1 and 
10.0 using -Ox and everything worked as expected.  Which Intel compiler 
version are you using?

HTH, John.