[MINC-development] -O3 breaks N3

[Claude LEPAGE]

Hi,

I think the damping of 1.0e-7 might be a little bit too
aggressive and not enough damping can cause the matrix
system to be ill-conditioned. While it works in most cases,
a value of 1.0e-6 will give similar results and will be 
more robust numerically. Can you try that? 

Claude

> Hello Everybody,
>
> Turns out that N3 is broken with -O2. Actually , compiling 
> http://packages.bic.mni.mcgill.ca/tgz/N3-1.12.0.tar.gz
> using standard ./configure & make
>
> produces a code which seem to work, but essentially corrects nothing at 
> least when applied to icmb 00100 t1w scan :
> ( 
> /data/ipl/user01/rotor/icbm_recovery/shell-pipe-analy-circa2006/native/mni_icbm_00100.001.t1.mnc.gz 
> on the bic system)
>
> it produces an imp file :
>
> MNI Field File
> %Wed Apr 18 18:40:53 2012>>> /opt/minc2/bin/nu_estimate_np_and_em 
> -parzen -log -sharpen 0.1 0.01 -iterations 100 -stop 0.0001 -shrink 4 
> -auto_mask -nonotify -b_spline 1.0e-7 -distance 200 -quiet -execute 
> -clobber -nokeeptmp -tmpdir /tmp/nu_correct_7795/ 
> mni_icbm_00100.001.t1.mnc auto_mni_icbm_00100.001.t1.nuc.imp
> Version = 0.9.0;
> Field_Type = B_Spline;
> Distance = 200;
> Domain =
>       -81.519097598907     89.3619937534825
>       -95.84404     164.15596
>       -155.813426545559     107.579156148442;
> Coefficients =
>      6.93367797718816e-310
>      6.93367797718816e-310
>                          0
>                          0
>                          0
> ...(all zeroes)
>                          0;
>
> When compiled on ubuntu 11.04 , gcc version 4.5.2
>
> Interestingly, the same tool compiled on Debian 5, gcc version 4.3.4
> works as expected.
>
>
>
>
> On 12-04-15 07:41 AM, Andrew Janke wrote:
> > Absolutely...
> >
> > Claude, remember also the bug we fixed in EBTKS's spline
> > implementation a long time back that was causing crashed on some files
> > with certain magic dimensions. I can't think of how this might break
> > anything (we added an episilon IIRC) but it was a change we had to
> > make.
> >
> > I for one am keen to keep N3 as it is and I don't see it being a
> > problem to force -02 behaviour during the compile. I have used N4 but
> > often revert to N3, probably because it's a beast I know.
>
>
> -- 
> Best regards,
>
> Vladimir S. FONOV ~ vladimir <dot> fonov <at> gmail <dot> com
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