$ cat idiocy.f90
module mathOps
    contains
    attributes(global) subroutine saxpy(x, y, a)
    implicit none
    real :: x(:), y(:)
    real, value :: a
    integer :: i, n
    n = size(x)
    i = blockDim%x * (blockIdx%x - 1) + threadIdx%x
    if (i <= n) y(i) = y(i) + a*x(i)
    end subroutine saxpy
end module mathOps

program testSaxpy
    use mathOps
    use cudafor
    implicit none
    integer, parameter :: N = 40000
    real :: x(N), y(N), a
    real, device :: x_d(N), y_d(N)
    type(dim3) :: grid, tBlock

    tBlock = dim3(256,1,1)
    grid = dim3(ceiling(real(N)/tBlock%x),1,1)

    x = 1.0; y = 2.0; a = 2.0
    x_d = x
    y_d = y
    call saxpy<<<grid, tBlock>>>(x_d, y_d, a)
    y = y_d
    write(*,*) 'Max error: ', maxval(abs(y-4.0))
end program testSaxpy

$ ldd idiocy
    linux-vdso.so.1 =>  (0x00007ffcac1e9000)
    libcudafor80.so => /opt/pgi/linux86-64/18.4/lib/libcudafor80.so (0x00007f3b5be46000)
    libcudafor.so => /opt/pgi/linux86-64/18.4/lib/libcudafor.so (0x00007f3b57dd1000)
    libcublas.so.8.0 => /opt/pgi/linux86-64/2018/cuda/8.0/lib64/libcublas.so.8.0 (0x00007f3b55421000)
    libcusparse.so.8.0 => /opt/pgi/linux86-64/2018/cuda/8.0/lib64/libcusparse.so.8.0 (0x00007f3b52913000)
    libcurand.so.8.0 => /opt/pgi/linux86-64/2018/cuda/8.0/lib64/libcurand.so.8.0 (0x00007f3b4e9a9000)
    libcudaforwrapblas.so => /opt/pgi/linux86-64/18.4/lib/libcudaforwrapblas.so (0x00007f3b4e770000)
    libcudart.so.8.0 => /opt/pgi/linux86-64/2018/cuda/8.0/lib64/libcudart.so.8.0 (0x00007f3b4e50a000)
    libcudafor2.so => /opt/pgi/linux86-64/18.4/lib/libcudafor2.so (0x00007f3b4e308000)
    libpgf90rtl.so => /opt/pgi/linux86-64/18.4/lib/libpgf90rtl.so (0x00007f3b4e0e5000)
    libpgf90.so => /opt/pgi/linux86-64/18.4/lib/libpgf90.so (0x00007f3b4db44000)
    libpgf90_rpm1.so => /opt/pgi/linux86-64/18.4/lib/libpgf90_rpm1.so (0x00007f3b4d941000)
    libpgf902.so => /opt/pgi/linux86-64/18.4/lib/libpgf902.so (0x00007f3b4d72d000)
    libpgftnrtl.so => /opt/pgi/linux86-64/18.4/lib/libpgftnrtl.so (0x00007f3b4d4fc000)
    libpgmp.so => /opt/pgi/linux86-64/18.4/lib/libpgmp.so (0x00007f3b4d27a000)
    libnuma.so => /opt/pgi/linux86-64/18.4/lib/libnuma.so (0x00007f3b4d079000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f3b4ce37000)
    libpgmath.so => /opt/pgi/linux86-64/18.4/lib/libpgmath.so (0x00007f3b4c97f000)
    libpgc.so => /opt/pgi/linux86-64/18.4/lib/libpgc.so (0x00007f3b4c736000)
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f3b4c52e000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f3b4c227000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f3b4be5e000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f3b4bc47000)
    /lib64/ld-linux-x86-64.so.2 (0x000055942ca2c000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f3b4ba42000)
    libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f3b4b72f000)

$ pgf90 -Mcuda=cc50 -o idiocy idiocy.f90

$ ./idiocy
 Max error:     0.000000