Description of packed

packed<int MemLoc=internal>		Programmers Guide
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Category:containers,selectors

Component type:type

Description

This storage type is equivalent to the BLAS/LAPACK packed storage format. The packed storage format is similar to the banded format, except that the storage for each row/column of the band is variable so there is no wasted space. This is better for efficiently storing triangular matrices.

 [  1   2   3   4   5  ]
 [  0   6   7   8   9  ]
 [  0   0  10  11  12  ]
 [  0   0   0  13  14  ]
 [  0   0   0   0  15  ]

 [  1   2   3   4   5  ]
 [  6   7   8   9  ]
 [  10  11  12  ]
 [  13  14  ]
 [  15  ]

 mapped to linear memory with row-major order:

 [  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  ]

Example

In tri_pack_vect.cc:

  typedef matrix< double, 
                  triangle<lower>, 
                  packed<external>, 
                  column_major >::type Matrix; 
  typedef dense1D<double> Vector;
  //         1               3
  //     A = 2  4       x =  2
  //         3  5  6         1
  const Matrix::size_type N = 3;
  double dA[] = { 1, 2, 3, 4, 5, 6 };
  Matrix A(dA, N, N);
  Vector x(N), Ax(N);
  for (unsigned int i = 0; i < N; ++i)
    x[i] = 3-i;
  mult(A, x, Ax);

Definition

Template Parameters

Parameter	Description	Default
`MemLoc`	Specify whether the memory used is "owned" by the matrix or if it was provided to the matrix from some external source (with a pointer to some data)	`internal`

Model of

Members

Member	Where defined	Description
`size_type`
`enum { id = PACKED, oned_id, ext=MemLoc, issparse=0, index }`

New members

Notes

See also