`zgemv:`procedure`xGEMV`performs the matrix-vector multiply-add operation of the form`y := alpha*op( A )*x + beta*y`, where`op( X )`is one of`op( A ) = A`or`op( A ) = A'`.`ALPHA`and`BETA`are scalars, and`A`is an`M x N`matrix.`X`is a vector of size`(1 + ( N - 1 ) * abs(INCX))`when argument`TRANS`is`NoTrans`, and`(1 + ( M - 1 ) * abs(INCX))`otherwise.`Y`is a vector of size`(1 + ( M - 1 ) * abs(INCY))`when argument`TRANS`is`NoTrans`, and`(1 + ( N - 1 ) * abs(INCY))`otherwise.