A packed storage matrix, also known as packed matrix, is a term used in programming for representing an matrix. It is a more compact way than an m-by-n rectangular array by exploiting a special structure of the matrix.
Typical examples of matrices that can take advantage of packed storage include:
The packed storage matrix allows a matrix to be converted to an array, shrinking the matrix significantly. In doing so, a square matrix is converted to an array of length .
Consider the following upper matrix:
which can be packed into the one array:
Similarly the lower matrix:
can be packed into the following one dimensional array:
Both of the following storage schemes are used extensively in BLAS and LAPACK.
An example of packed storage for Hermitian matrix:
An example of packed storage for banded matrix: