## Developer Reference

• 2020.2
• 07/15/2020
• Public Content
Contents

# DSS Distributed Symmetric Matrix Storage

The distributed assembled matrix input format can be used by the Parallel Direct Sparse Solver for Clusters Interface.
In this format, the symmetric input matrix
A
is divided into sequential row subsets, or domains. Each domain belongs to an MPI process. Neighboring domains can overlap. For such intersection between two domains, the element values of the full matrix can be obtained by summing the respective elements of both domains.
As in the centralized format, the distributed format uses three arrays to describe the input data, but the
values
,
columns
, and
rowIndex
arrays on each processor only describe the domain belonging to that particular processor and not the entire matrix.
For example, consider a symmetric matrix
A
: This array could be distributed between two domains corresponding to two MPI processes, with the first containing rows 1 through 3, and the second containing rows 3 through 5.
For the symmetric input matrix, it is not necessary to store the values from the lower triangle. one-based indexing values = (6 -1 -3 5 3 2) columns = (1 2 4 2 3 5) rowIndex = (1 4 5 7) zero-based indexing values = (6 -1 -3 5 3 2) columns = (0 1 3 1 2 4) rowIndex = (0 3 4 6) one-based indexing values = (8 5 2 10 5) columns = (3 4 5 4 5) rowIndex = (1 4 5 6) zero-based indexing values = (8 5 2 10 5) columns = (2 3 4 3 4) rowIndex = (0 3 4 5)
The third row of matrix
A
is common between domain 1 and domain 2. The values of row 3 of matrix
A
are the sums of the respective elements of row 3 of matrix
A
Domain1
and row 1 of matrix
A
Domain2
.

## 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