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<font size=3>Hi,<br><br>
The itk/vxl::LBFGS(B)Optimizer implementation IS multivariate. The
'multivariate' label refers to the number of variables (input arguments
of the cost function) over which is optimised. <br><br>
the optimisaton problem is:<br><br>
min_x f(x)<br><br>
On the site
<a href="http://www.alglib.net/optimization/" eudora="autourl">http://www.alglib.net/optimization/</a>
a multivariate optimisation method means that dim(x) >1 is
allowed.<br><br>
The LBFGSOptimizer is not suitable for MultipleValuedCostFucnction, as
far as I know, only for SingleValuedCostFunctions.<br><br>
singlevalued means: dim(f) = 1<br>
multiplevalued means: dim(f) > 1<br><br>
The vnl_cost_function indeed inherits from the vnl_unary_function, but
the vnl_unary_function is templated over a vector of doubles, which
contains the input argument x:<br><br>
class vnl_cost_function : public vnl_unary_function<double,
vnl_vector<double> ><br><br>
with kind regards,<br>
stefan<br><br>
<br>
At 08:35 7-11-2007, Luis Ibanez wrote:<br><br>
<br>
<blockquote type=cite class=cite cite>Hi Ali,<br><br>
<br>
1) It is not a "problem", it is an "implementation
feature". :-)<br><br>
<br><br>
2) It is not in ITK, it is in VXL,<br><br>
Please look at the implementation in the file:<br><br>
Insight/Utilities/vxl/core/vnl/vnl_lbfgs.h<br><br>
Where the optimizer takes as input a vnl_cost_function<br>
object, that derives from the vnl_unary_function
class.<br><br>
<br><br>
3) It will be great to have multi-variate implementations<br>
of these optimizers. If you are motivated to write
one,<br>
it will make a great contribution to the Insight
Journal.<br><br>
<br><br>
Regards,<br><br>
<br>
Luis<br><br>
<br><br>
-------------<br>
Ali - wrote:<br>
<blockquote type=cite class=cite cite>Hi,<br>
The VNL wrappers itk::LBFGSBOptimizer and itk::LBFGSOptimizer are
classified as single-variant optimiser, while being based on the
quasi-Newton method, they are multi-variant optimisers by nature -- see
<a href="http://www.alglib.net/optimization/" eudora="autourl">http://www.alglib.net/optimization/</a>
. Is this the ITK wrapper problem or a VNL issue?<br>
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