The *SMAT command has an option to allocate a sparse matrix using
the CSR format. This format represents a matrix by three one-dimensional arrays. The
arrays are specified in the Val2,
Val3, and Val4 fields of
*SMAT and contain the following data:
| 1st array: nonzero values |
| 2nd array: the extents of rows (this vector stores the locations in the values vector that start a row) |
| 3rd array: column indices |
For example, consider this 4 x 4 matrix M:
The matrix can be described by these three vectors:
A = [ 1 2 4 3 5 -1 2
] | This array is of length NNZ (number of
nonzero values) and holds all the nonzero entries of M. | |||
IA = [ 1 4 5 6 8
] | This array is of length m+1
(m is the size of the matrix), and is
defined by the recursive definition:
| |||
JA = [ 1 2 3 2 3 3 4
] | This array is of length NNZ and holds the
column indices of the nonzero values of the matrix. |
The following APDL commands create the above matrix.
DIM=4 NNZ=7 *VEC,A,D,ALLOC,NNZ A(1)=1,2,4,3,5,-1,2 *VEC,IA,L,ALLOC,DIM+1 IA(1)=1,4,5,6,8 *VEC,JA,I,ALLOC,NNZ JA(1)=1,2,3,2,3,3,4 *SMAT,M,D,ALLOC,CSR,IA,JA,A,FALSE *PRINT,M