stdlib_zgeru Subroutine

     pure subroutine stdlib_zgeru(m,n,alpha,x,incx,y,incy,a,lda)
     !! ZGERU performs the rank 1 operation
     !! A := alpha*x*y**T + A,
     !! where alpha is a scalar, x is an m element vector, y is an n element
     !! vector and A is an m by n matrix.
        ! -- reference blas level2 routine --
        ! -- reference blas is a software package provided by univ. of tennessee,    --
        ! -- univ. of california berkeley, univ. of colorado denver and nag ltd..--
           ! Scalar Arguments 
           complex(dp), intent(in) :: alpha
           integer(ilp), intent(in) :: incx, incy, lda, m, n
           ! Array Arguments 
           complex(dp), intent(inout) :: a(lda,*)
           complex(dp), intent(in) :: x(*), y(*)
        ! =====================================================================
           
           ! Local Scalars 
           complex(dp) :: temp
           integer(ilp) :: i, info, ix, j, jy, kx
           ! Intrinsic Functions 
           intrinsic :: max
           ! test the input parameters.
           info = 0
           if (m<0) then
               info = 1
           else if (n<0) then
               info = 2
           else if (incx==0) then
               info = 5
           else if (incy==0) then
               info = 7
           else if (lda<max(1,m)) then
               info = 9
           end if
           if (info/=0) then
               call stdlib_xerbla('ZGERU ',info)
               return
           end if
           ! quick return if possible.
           if ((m==0) .or. (n==0) .or. (alpha==czero)) return
           ! start the operations. in this version the elements of a are
           ! accessed sequentially with cone pass through a.
           if (incy>0) then
               jy = 1
           else
               jy = 1 - (n-1)*incy
           end if
           if (incx==1) then
               do j = 1,n
                   if (y(jy)/=czero) then
                       temp = alpha*y(jy)
                       do i = 1,m
                           a(i,j) = a(i,j) + x(i)*temp
                       end do
                   end if
                   jy = jy + incy
               end do
           else
               if (incx>0) then
                   kx = 1
               else
                   kx = 1 - (m-1)*incx
               end if
               do j = 1,n
                   if (y(jy)/=czero) then
                       temp = alpha*y(jy)
                       ix = kx
                       do i = 1,m
                           a(i,j) = a(i,j) + x(ix)*temp
                           ix = ix + incx
                       end do
                   end if
                   jy = jy + incy
               end do
           end if
           return
     end subroutine stdlib_zgeru