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Teuchos: Avoids spurious warning in BLAS when using empty vectors

James Willenbring requested to merge mdavezac:master into master

Created by: mdavezac

BLAS routines require a leading dimension parameter which nmust be at least 1. However, it comes out at zero in distributed multi-vectors where one or more processes have zero elements. The BLAS wrappers in Teuchos now check for this corner case and make sure ld(a|b|c) are always >= 1. For instance, vectors with zero elements occur when wrapping block-cyclic scalapack row vectors on grids axb, with b > 1. Processes with column index >= 1 receive 0 elements from row vectors.

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