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

[Luis Ibanez]

Hi Kent,

<me speculating>

One of the things that -O3 does is to force full in-lining of templated method.

I'm wondering if the effect is that something that has been typically delegated
to a cxx initialization is now being done in a header.

That said...
the default of "Release" build in Linux is to use -O3....
so...the problem that you are exposing seems to
be very specific to OS X.

</me speculating>


Question:

When you changed the flags...
Did you rebuild the toolkit from scratch ?


     Luis


------------------------
On Thu, Oct 22, 2009 at 4:36 PM, kent williams
<norman-k-williams at uiowa.edu> wrote:
> I’m trying to build ITK from the CVS source as of today.  I’m 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 didn’t  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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