Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

ID 766686
Date 11/07/2023
Public

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DSS Nonsymmetric Matrix Storage

For a non-symmetric or non-Hermitian matrix, all non-zero elements need to be stored. Consider the non-symmetric matrix B:



The matrix B has 13 non-zero elements, and all of them are stored as follows:

Storage Arrays for a Non-Symmetric Matrix
one-based indexing                            
values = (1 -1 -3 -2 5 4 6 4 -4 2 7 8 -5)
columns = (1 2 4 1 2 3 4 5 1 3 4 2 5)
rowIndex = (1 4 6 9 12 14)              
zero-based indexing                            
values = (1 -1 -3 -2 5 4 6 4 -4 2 7 8 -5)
columns = (0 1 3 0 1 2 3 4 0 2 3 1 4)
rowIndex = (0 3 5 8 11 13)              

Storage Format Restrictions

The storage format for the sparse solver must conform to two important restrictions:

  • the non-zero values in a given row must be placed into the values array in the order in which they occur in the row (from left to right);

  • no diagonal element can be omitted from the values array for any symmetric or structurally symmetric matrix.

The second restriction implies that if symmetric or structurally symmetric matrices have zero diagonal elements, then they must be explicitly represented in the values array.