The timescale is in milliseconds? A modeller can create an occlusion map for such a scene in a few seconds: if that's the case and it required roughly two minutes even reducing the time and improving quality it's still better to just create and save an occlusion/light map with an existing tool. It could be a start if your intend to create your own lightmapper though. What baffles me is that looks more like vertex lighting then a per-pixel map.
To speed up the rendering you could use a random distribution instead of going through every iteration, and then blur the resulting map to reduce the noise (most occlusion systems let you adjust rendering's precision).
To speed up the rendering you could use a random distribution instead of going through every iteration, and then blur the resulting map to reduce the noise (most occlusion systems let you adjust rendering's precision).