title: Different OpenGL behaviour on different hardware
body: <p>I have an application that uses OpenGL to draw output images. For testing purposes I'm trying to create reference images and then use precision hash to compare them to program output. While it works flawlessly within a context of a single computer I've encountered strange problems when using the same approach with computers running different GPUs. While the images generated on different GPUs appear absolutely identical to human eye they cannot pass prescision hash test when compared to one another and per-pixel comparison reveals that there are several pixels that are &quot;off&quot;. I've been trying to find problems in my code for several days to no avail and this behaviour manifests itself on all the shaders that I use. Could this possibly be due to differences in OpenGL implementation from different hardware manufacturers? Is it a valid approach to compare images generated on different GPUs with phash for testing purposes?</p>