op_inv_meat.hpp

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// Copyright (C) 2010 NICTA and the authors listed below
// http://nicta.com.au
// 
// Authors:
// - Conrad Sanderson (conradsand at ieee dot org)
// 
// This file is part of the Armadillo C++ library.
// It is provided without any warranty of fitness
// for any purpose. You can redistribute this file
// and/or modify it under the terms of the GNU
// Lesser General Public License (LGPL) as published
// by the Free Software Foundation, either version 3
// of the License or (at your option) any later version.
// (see http://www.opensource.org/licenses for more info)


//! \addtogroup op_inv
//! @{


//! immediate inverse of a matrix, storing the result in a dense matrix
template<typename eT>
inline
void
op_inv::apply(Mat<eT>& out, const Mat<eT>& A)
  {
  arma_extra_debug_sigprint();
  
  // no need to check for aliasing, due to:
  // - auxlib::inv() copies A to out before inversion
  // - for 2x2 and 3x3 matrices the code is alias safe
  
  arma_debug_check( !A.is_square(), "op_inv::apply(): matrix must be square" );
  
  const bool status = (&out != &A) ? auxlib::inv_noalias(out, A) : auxlib::inv_inplace(out);
  
  if(status == false)
    {
    arma_warn( true, "inv(): matrix appears to be singular" );
    out.set_size(0,0);
    }
  }



//! immediate inverse of T1, storing the result in a dense matrix
template<typename T1>
inline
void
op_inv::apply(Mat<typename T1::elem_type>& out, const Op<T1,op_inv>& X)
  {
  arma_extra_debug_sigprint();
  
  typedef typename T1::elem_type eT;
  
  const strip_diagmat<T1> strip(X.m);
  
  if(strip.do_diagmat == true)
    {
    op_inv::apply_diag(out, strip.M);
    }
  else
    {
    const unwrap<T1>   tmp(X.m);
    const Mat<eT>& A = tmp.M;
  
    op_inv::apply(out, A);
    }
  }



template<typename T1>
inline
void
op_inv::apply_diag(Mat<typename T1::elem_type>& out, const Base<typename T1::elem_type, T1>& X)
  {
  arma_extra_debug_sigprint();
  
  typedef typename T1::elem_type eT;
  
  const diagmat_proxy_check<T1> A(X.get_ref(), out);
  
  const u32 N = A.n_elem;
  
  out.set_size(N,N);
  
  for(u32 col=0; col<N; ++col)
    {
    for(u32 row=0; row<col; ++row)   { out.at(row,col) = eT(0); }
    
    out.at(col,col) = eT(1) / A[col];
    
    for(u32 row=col+1; row<N; ++row) { out.at(row,col) = eT(0); }
    }
  
  }



//! @}