[Insight-developers] vnl_math::pi coming up undefined with vector optimization turned on?

[kent williams]

I¹m trying to build ITK from the CVS source as of today.  I¹m not modifying
anything at all.  The only thing I did was use our CFLAGS and CXXFLAGS when
I run CMake.  The undefined externals are coming during building ITK itself,
not in my application.

The problem didn¹t  show up until I added ­O3 to the command line.  Why that
would interact with the static const members of  vnl_math I have no idea.


On 10/22/09 3:21 PM, "Bradley Lowekamp" <blowekamp at mail.nih.gov> wrote:

> Hello kent,
> 
> I was just looking at this stuff. It turns out the following is not standard
> c++:
> 
> class C {
> static const double one = 1.0;
> };
> 
> This is because static member variable must be defined in one obj file, not in
> headers, so that all instance of the object will reference the same address.
> But some compilers are smart enough to know what you are trying to do here and
> let is slide.
> 
> As to why you are getting this error, are you sure you are linking against the
> correct libraries? vnl_math::pi should be defined int the vnl library.
> 
> victoria:bin blowek1$ nm libitkvnl.a | grep pi
> 000016d8 S __ZN8vnl_math11one_over_piE
> 000016e0 S __ZN8vnl_math11two_over_piE
> 000016e8 S __ZN8vnl_math15two_over_sqrtpiE
> 000016f0 S __ZN8vnl_math16one_over_sqrt2piE
> 000016c0 S __ZN8vnl_math2piE
> 000016c8 S __ZN8vnl_math9pi_over_2E
> 000016d0 S __ZN8vnl_math9pi_over_4E
> 
> Hope this helps,
> Brad
> 
> 
> 
> On Oct 22, 2009, at 4:05 PM, kent williams wrote:
> 
>> I'm trying to build ITK on OS X with the "-O3" flag. I've never had trouble
>> with "-O2" but now I get an undefined external for vnl_math::pi.
>> 
>> The main reason to go with "-O3" is to turn on vector SIMD optimizations --
>> in one application we're trying to optimize, the biggest share of CPU is
>> used in the ImageToImageMetric, and Shark is suggesting that the loops in
>> the hot routines would benefit from vector optimizations.
>> 
>> I don't know why or from whence the problem originates, but what it looks
>> like is that the vnl_math:: constants don't get declared as variables if
>> VCL_STATIC_CONST_INIT_FLOAT_NO_DEFN is defined.
>> 
>> Now I'm no VXL library hacker,so I'm pretty much baffled by this thing.
>> 
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> 
> ========================================================
> 
> Bradley Lowekamp 
> 
> Lockheed Martin Contractor for
> 
> Office of High Performance Computing and Communications
> 
> National Library of Medicine
> 
> blowekamp at mail.nih.gov
> 
> 
> 

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