What is the purpose of pointerE array in the CSR sparse matrix format?

[Eugene_Pavlov]

What is the purpose of pointerE array in the CSR sparse matrix format, if pointerB already contains enough information about start and end of a particular row?

@https://software.intel.com/content/www/us/en/develop/documentation/mkl-developer-reference-c/top/appendix-a-linear-solvers-basics/sparse-matrix-storage-formats/sparse-blas-csr-matrix-storage-format.html

[Kirill_V_Intel]

Hi Eugene,

The purpose of having pointerE is to allow working with a submatrix of a given sparse matrix. In other words, it allows the user to have a sparse matrix but use only a part of it in computations, essentially by skipping elements from the end of each row (being pointed to by pointerE[i], ... pointerB[row+1] in the column indices and values arrays).
By having also a pointerB different from some general rowStart of a given matrix, the user can also skip some elememnts from the beginning of each row.

Let us know if you have further questions.

Best,
Kirill

[Gennady_F_Intel]

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