equihash192_7.cl's decompress/decompress2 used double + sqrt behind
cl_khr_fp64, so the kernel failed to build on OpenCL stacks without fp64
(notably rusticl/Mesa) — those workers died with 'use of type double requires
cl_khr_fp64'. Replace round(sqrt(2*x+1)) with an exact integer square root
(single-precision estimate corrected to the integer floor, then rounded; inputs
are triangular indices < ~2^26). No fp64, no behavior change on ROCm (verified
bit-identical: 77 solutions/40 nonces, same as before), and rusticl devices now
build and solve correctly.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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