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conformance: promote takum8 to bit-precise + fix takum arXiv citation (61->62/83) - #1222
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… (61->62/83) Track A of the parallel wave-loop. Stacked on #1221 (6-format promotion). WHAT: - takum8: structural -> bit-precise. Dedicated logarithmic decoder (value = exp(ell/2), ell = (-1)^S*(c+m), base sqrt(e)) added to gen_all_formats.py as make_takum_decoder(n). Exhaustive over all 256 codes; correctly-rounded-nearest-even f64 (min gap to midpoint = 0.0135 x 0.5 ULP -> 200-bit mpmath sufficient). LUT cross-checked vs libtakum/src/codec.c (formulaic assert). [proven] - takum16/32/64: HONESTLY kept structural. Values transcendental; the exhaustive correctly-rounded gap is NOT verifiable without an external libtakum oracle (no independent second witness). Not promoted. CITATION FIX: - takum entries cited arXiv:2412.20273 (that is 'Integer Representations in IEEE 754, Posit, and Takum', a different/later paper). The format-DEFINING reference is arXiv:2404.18603 ('Beating Posits at Their Own Game: Takum Arithmetic', CoNGA 2024, logarithmic takum). Fixed in SSOT specs/numeric/formats_catalog.t27 and forward-facing docs (NUMERIC_FORMATS_SSOT, POSITIONING_CONFORMANCE_LAYER, RESEARCH_CLAIMS). gen/numeric polyglot bindings left untouched (managed by a separate 77->83 regeneration effort). NOW.md changelog history left intact. CAVEAT: takum standard guarantees apply for n>=12, so takum8 is below the nominal threshold; this is recorded in the pack notes, not a decoder error. COUNT: strict SW-bitexact 61 -> 62/83; structural 16 -> 15; selfconsistent 6. Conformance gate: CLEAN. Self-test gates: PASS. takum8 256/256 self-test PASS. decode-HW / compute-HW unaffected (stay 0/83 until real AX7203 run). Closes #1223
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Track A — takum8 → bit-precise (61→62/83)
Stacked on #1221 (6-format promotion). Base =
feat/conformance-promote-6-structural-bitexact. Merge #1221 first.Что сделано
value = exp(ell/2),ell = (-1)^S·(c+m), базаsqrt(e)) вgen_all_formats.pyкакmake_takum_decoder(n). Exhaustive по всем 256 кодам, correctly-rounded-nearest-even f64 (минимальный зазор до midpoint = 0.0135 × 0.5 ULP → 200-бит mpmath достаточно). LUT сверена сlibtakum/src/codec.c(формульный assert).Правка цитаты
Записи takum цитировали
arXiv:2412.20273— это «Integer Representations in IEEE 754, Posit, and Takum» (другая, более поздняя работа). Формат-определяющая ссылка = arXiv:2404.18603 («Beating Posits at Their Own Game: Takum Arithmetic», CoNGA 2024, логарифмический takum). Исправлено в SSOTspecs/numeric/formats_catalog.t27и forward-facing docs (NUMERIC_FORMATS_SSOT,POSITIONING_CONFORMANCE_LAYER,RESEARCH_CLAIMS).gen/numeric/полиглот-биндинги НЕ тронуты (управляются отдельным 77→83 регенератором).NOW.mdchangelog оставлен как есть (историческая запись).Оговорка
Стандарт takum гарантирует свойства для n≥12, поэтому takum8 формально ниже номинального порога — отмечено в notes пакета, это НЕ ошибка декодера.
Проверки
Honesty
encoding ≠ compute ≠ FPGA. decode-HW и compute-HW не затронуты — остаются 0/83 до реального прогона на AX7203. bit-precise (независимый декодер, abs_error=0) НЕ приравнивается к bitexact_selfconsistent.Closes #1223