Lower and Upper Triangle Portions of a Sparse Matrix

[rizwanashraf]

Include support for extracting the Lower ($L$) and Upper ($U$) Triangle portions of a Sparse Matrix, i.e., $A = L + U$.

The decomposition includes a strictly lower triangular matrix, i.e., $L_{ij} = [ a_{ij} ~~ for ~~ i > j;~ 0~~ for~~ i <= j ] $, and an upper triangular matrix, i.e., $U_{ij} = [ a_{ij} ~~ for ~~ i <= j;~ 0~~ for~~ i > j ] $.

Currently, sparse matrices are supported and the following storage formats are supported: CSR, COO.

The following is an example of extracting the lower triangular portion of a sparse matrix in COMET DSL:

L[i, j] = read_lowerTri_from_file(0);

The following is an example of extracting the upper triangular portion of a sparse matrix in COMET DSL:

U[i, j] = read_upperTri_from_file(0);