[PROTOTYPE] Add fallback to legacy scan implementation for CPU devices and devices that lack size 32 sub-groups

oneapi-src / oneDPL

oneAPI DPC++ Library (oneDPL) https://software.intel.com/content/www/us/en/develop/tools/oneapi/components/dpc-library.html

Apache License 2.0

720 stars 114 forks source link

Closed mmichel11 closed 1 month ago

mmichel11 commented 1 month ago

This PR adds a fallback from reduce-then-scan to the legacy scan implementation in two separate cases:

As a fallback if the device does not support size 32 sub-groups. We explicitly require this size and must fallback if it's not supported.
For CPU devices. The sub-group level operations do not translate well to CPU devices and the legacy implementation is significantly faster on CPUs.

mmichel11 commented 1 month ago

Moving back to draft. Some issues occurred when merging with the target branch.

Update: The issues have been fixed.