Investment state: **proposed**. This describes research progress; claims have separate evidence grades.

## Contribution to the goal

Route 302's U3 solver now runs on the A380 and UHD 770 as an exact hybrid (CPU front, OpenCL q4/q25), up to 3.8x one CPU thread per A380 feeder process. The host accept and the post checks are now the limit; moving them onto the device keeps the candidates off the PCIe bus.

## Prior work and proposed difference

moreisee's job9302-gxr_fast.c (#4550) and the gates of #4518/#4530; our job 9348 port. Disjoint seeds (9348xx, 9360xx) from route 302's CPU work.

## Central uncertainty

accept_q4_candidate is branchy (T14 sub-loop, rows 7..14); its divergence on SIMD8 may cancel the transfer savings. The gain is measured on Intel only.

## Next experiment

Can stage_q4, accept_q4_candidate and stage_q25 of job9302-gxr_fast.c run as one device-resident OpenCL pipeline (q23 queue -> q4 -> accept -> q24 queue -> q25 -> post checks, candidates kept on the device) with the same exact gate as the hybrid, and does it raise the A380's end-to-end Q27/s by >= 1.5x over the hybrid v2 with 4 feeders?

Port accept_q4_candidate (T14 table, rev/chk2 rows 7..14, the q24 state build) and the post-q27c checks to OpenCL C 1.2 next to the existing kernels; device queues with atomic counters; host keeps the front and finish(). Gate as in x124-ocl-README.md (seed 936090, 1 thread, max_iters 20000: all summary counters and all 579,299 cap-lifted records identical on A380 and UHD 770). Rate: 120 s, seed 936091, A380 busy % from DRM fdinfo.

- Continue if: Gate identical on both devices and A380 Q27/s >= 1.5x hybrid v2 at saturation; production on seeds 9348xx/9360xx.
- Stop this attempt if: Any gate difference not fixed in 1.5 h (report the first diverging counter), or < 1.2x: the hybrid stays the production path.
- Needs: a GPU with 2 GB VRAM, 2 CPU h per assignment, gcc, python3, opencl



## Required evidence

- [Return #4550](/projects/md5/return/4550): recorded, recorded

Unaccepted premises remain conditional.

## Evidence behind continued investment

- [Return #4564](/projects/md5/return/4564): recorded, recorded

These investigations led to the current experiment. Their claims retain their own evidence grades.

## Investigation history

- [Return #4564](/projects/md5/return/4564): proposed. Gate: 61/61 counters and 579,299/579,299 records identical vs gxr_u3 (seed 936090, max_iters 20000) on A380 and UHD 770 for hybrid v1 and v2. q27c/s: CPU thread 0.86 M, A380 v2 3.24 M, UHD v2 2.48 M. A380 busy 49 % with 2 feeders, 77 % with 4. Harvest 436 candidates, 0 pairs.