fn_rank.hpp

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00001 // Copyright (C) 2010 NICTA and the authors listed below
00002 // http://nicta.com.au
00003 // 
00004 // Authors:
00005 // - Conrad Sanderson (conradsand at ieee dot org)
00006 // - Dimitrios Bouzas (dimitris dot mpouzas at gmail dot com)
00007 // 
00008 // This file is part of the Armadillo C++ library.
00009 // It is provided without any warranty of fitness
00010 // for any purpose. You can redistribute this file
00011 // and/or modify it under the terms of the GNU
00012 // Lesser General Public License (LGPL) as published
00013 // by the Free Software Foundation, either version 3
00014 // of the License or (at your option) any later version.
00015 // (see http://www.opensource.org/licenses for more info)
00016 
00017 
00018 //! \addtogroup fn_rank
00019 //! @{
00020 
00021 
00022 
00023 template<typename T1>
00024 inline
00025 arma_warn_unused
00026 u32
00027 rank(const Base<typename T1::elem_type,T1>& X, typename T1::pod_type tol = 0.0)
00028   {
00029   arma_extra_debug_sigprint();
00030   
00031   typedef typename T1::elem_type eT;
00032   typedef typename T1::pod_type   T;
00033   
00034   const unwrap<T1>   tmp(X.get_ref());
00035   const Mat<eT>& A = tmp.M;
00036   
00037   Col<T> s;
00038   const bool status = auxlib::svd(s, A);
00039   
00040   if(status == true)
00041     {
00042     if(tol == T(0))
00043       {
00044       tol = (std::max)(A.n_rows, A.n_cols) * eop_aux::direct_eps(max(s));
00045       }
00046       
00047     // count non zero valued elements in s
00048     
00049     const T*  s_mem  = s.memptr();
00050     const u32 n_elem = s.n_elem;
00051           u32 count  = 0;
00052     
00053     for(u32 i=0; i<n_elem; ++i)
00054       {
00055       if(s_mem[i] > tol)
00056         {
00057         ++count;
00058         }
00059       }
00060     
00061     return count;
00062     }
00063   else
00064     {
00065     arma_print("rank(): singular value decomposition failed");
00066     return u32(0);
00067     }
00068    
00069   }
00070 
00071 
00072 
00073 //! @}