Just wanted to share the link to https://software.intel.com/en-us/articles/adaptive-screen-space-ambient-occlusion / https://github.com/GameTechDev/ASSAO if anyone's interested.

It's in quality similar to HBAO+ (the core is based on horizon based ambient occlusion) but has lower (and higher) quality/performance presets, so it's easy to tune for lower/higher power hardware. For example, the "Low" preset is suitable for use on newer integrated graphics on laptops.

Current implementation is DX11-only but it's completely opensource (MIT license) so you can use it, port it and tweak it in any way you like :)

Minor update - due to popular requests I've added the "Lowest" preset - it processes only half of the pixels compared to Low, in a checkerboard pattern, and is about 55-60% of the cost of Low. Useful for really low-end HW!