"Floor" function produces artifacts in shader

Hello everyone, here is the output of the simple shader **tex2D( myTex , floor(i.uv*3)/3);** I need to do this to get a coherent noise from sampling an image. How can I avoid the flickering artifacts that appear? They appear in the middle, at points where i.uv.x/3=1, 2, 3 and i.uv.y/3=1, 2, 3 ![alt text][1] [1]: /storage/temp/102601-floor.png