[Mesa-dev] Determinism in the results of llvmpipe?

[Andrew A.]

Hello,

I'm using Mesa's software renderer for the purposes of regression
testing in our graphics software. We render various scenes, save a
screencap of the framebuffer for each scene, then compare those
framebuffer captures to previously known-good captures.

Across runs of these tests on the same hardware, the results seem to
be 100% identical. When running the same tests on a different machine,
results are *slightly* different. It's very similar within a small
tolerance, so this is still usable. However, I was hoping for fully
deterministic behavior, even if the hardware is slightly different.
Are there some compile time settings or some code that I can change to
get Mesa's llvmpipe renderer/rasterizer to be fully deterministic in
its output?

I'm using llvmpipe, and these are the two different CPUs I'm using to
run the tests:
Intel(R) Xeon(R) CPU E3-1275 v3
Intel(R) Xeon(R) CPU X5650

Thanks,

Andrew