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docs(sycl): close float_ssim combined formula residual row with measured evidence - #1684
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…red evidence PR #1645 (9e9ea05) already aligned float_ssim_sycl with CPU reference arithmetic in core/src/feature/sycl/integer_ssim_sycl.cpp (ssim_terms and ssim_term evaluate exact per-pixel l*c*s in fp32 pairs, fixed-point work-group sums, and double host reduction). Measured on Intel Arc A380 under Linux xe kernel driver against --backend cpu: - Netflix 576x324 (48 frames): max abs diff 0.000e+00 - BBB 3840x2160 auto scale: max abs diff 0.000e+00 - BBB 3840x2160 scale=1: max abs diff 0.000e+00 (down from 7.8e-5 before #1645) - Flat identical frames: exactly 72.247199 dB on both CPU and SYCL - test_sycl_twin_option_parity passes 13/13 Closes T-SYCL-FLOAT-SSIM-COMBINED-FORMULA-RESIDUAL-2026-09-29.
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Summary
Closes
T-SYCL-FLOAT-SSIM-COMBINED-FORMULA-RESIDUAL-2026-09-29.PR #1645 ($l \cdot c \cdot s$ in fp32 pairs
9e9ea0571) already alignedfloat_ssim_syclwith CPU reference arithmetic incore/src/feature/sycl/integer_ssim_sycl.cpp(ssim_termsandssim_termevaluate exact per-pixelFf, work-group fixed-point sumsterm_fixed, and double host reduction).Measurements on Intel Arc A380 (Linux
xedriver)Measured against
--backend cpuonryzen-4090-arcundersycl-a380.lock:python3 scripts/ci/run_meson_test.py -- -C build test_sycl_twin_option_parity: 13/13 passed (includingtest_float_ssim_lcsandtest_float_ssim_db_options, exact match on flat identical frames at 72.247199 dB).python3 scripts/ci/run_meson_test.py -- -C build test_sycl_float_ssim_parity: 3/3 passed.python3 scripts/ci/run_meson_test.py -- -C build test_sycl_float_ssim_parity_large: 3/3 passed.src01_hrc00_576x324.yuvvssrc01_hrc01_576x324.yuv(48 frames): max abs diff is 0.000e+00 (bit-identical to CPU).3840x2160, auto scale): max abs diff is 0.000e+00 (bit-identical to CPU).3840x2160, explicitscale=1): max abs diff is 0.000e+00 (bit-identical to CPU, down from 7.8e-5 before fix(sycl): RC3 parity follow-ups #1645).The residual is completely gone.
Reproducer / Verification Commands
Checklist
AGENTS.mdinvariant note — no rebase-sensitive invariants touched.changelog.d/fixed/sycl-float-ssim-combined-formula-residual.mddocs/rebase-notes.md