SimMatr.h

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#ifndef SimMatr_h
#define SimMatr_h
 
namespace SimMat {
 
// packing of symmetric matrices 'sm' in one-dimensional array 'pac_sm'
// 'pac_sm' MUST be large enough to receive n*(n+1)/2 elements
template <class T>
inline void pack2d(int n, const T* sm, T* pac_sm)
{
  for(int i = 0; i < n; i++) {
     for(int j = 0; j <= i; j++) {
        int k = i*(i+1)/2 + j;
        pac_sm[k] = sm[i*n+j];
     }
  }
}
 
// for a given i and j in 'sm' returns the index in 'pac_sm' 
inline int get_idx(int i,int j)
{
  return (i>j) ? i*(i+1)/2 + j : j*(j+1)/2 + i;
}
 
// for a given i and j return 'sm[i][j]'
template <class T>
inline T get_element(const T* pac_sm,int i,int j)
{
  return pac_sm[ get_idx(i,j) ];
}
 
// unpacks the 'pac_sm' in the symmetric matrix 'sm'
// 'sm' MUST be large enough to receive n*n elements
template <class T>
inline void unpack2d(int n, T* sm, const T* pac_sm)
{
  for(int i = 0; i < n; i++) {
     for(int j = 0; j <= i; j++) {
        int k = i*(i+1)/2 + j;
        sm[i*n+j] = sm[i+j*n] = pac_sm[k];
     }
  }
}
 
}
#endif