`dsbmv:`procedure`xSBMV`performs matrix-vector multiply-add operation of the form`y := alpha*A*B + beta*y`.`ALPHA`and`BETA`are scalars, and`A`is an`N x N`symmetric banded matrix, with`K`super-diagonals.`X`and`Y`are`N`element vectors.

`dsbmv:`procedure`xSBMV`performs matrix-vector multiply-add operation of the form`y := alpha*A*B + beta*y`.`ALPHA`and`BETA`are scalars, and`A`is an`N x N`symmetric banded matrix, with`K`super-diagonals.`X`and`Y`are`N`element vectors.