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Created by James Willenbring@jmwilleMaintainer

KokkosKernels: CrsMatrix sumIntoValuesSorted minor questions

Created by: mhoemmen

@bathmatt 's commit https://github.com/trilinos/Trilinos/commit/1e65cffac05ae95bbc4e6f0d6d4d428886704834 added a sumIntoValuesSorted method to KokkosSparse::CrsMatrix. I have a few comments and questions:

  1. We should introduce the "hint" that Epetra and Tpetra use for optimizing search for multiple column indices. It introduces an extra branch per input index, but avoids search for common cases. @etphipp first implemented it in Tpetra and found it to be useful, and findRelOffset (in tpetra/core/src/Tpetra_Util.hpp) does it too.
  2. It's legit to use ordinal_type (32-bit) instead of size_type (64-bit on everything but CUDA) for the difference between two consecutive row offsets, as long as the row doesn't have too many duplicate entries. SparseRowView(Const) already uses ordinal_type for the row length, for this reason.
  3. Was there a particular reason for the hi - low > 10 cut-off, or is that just a good guess?