Details:
- BLAS has a peculiar bug (or feature) whereby calling gemv on a vector
y of non-zero length and a vector x of zero length results in no action.
Given that the operation is y := beta*y + A*x, many (most?) individuals
would expect vector y to still be scaled by beta. BLIS, when called
natively, handles these cases intuitively (with beta scaling).
Unfortunately, many BLAS test suites actually check for the way this
situation is handled. Therefore, we have decided to implement this "bug"
in the compatibility layer so as to provide "bug-for-bug" compatibility
with BLAS.
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