conformance: promote 6 structural packs to bit-precise (IBM HFP, x87, NF4, GFTernary) (Closes #1076) - #1077
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… NF4, GFTernary)
Add dedicated reference codecs to gen_all_formats.py that turn 6 honest
structural placeholders into bit-precise round-trip packs (abs_error=0):
- ibm_hfp32/64/128: IBM Hexadecimal Floating Point, base-16 exponent
(S1:E7 excess-64:M), value = 0.M(2) * 16^(E-64); 3.0 = 0.1875 x 16^1
- x87_fp80: Intel 80-bit extended, explicit integer bit as MSB of the
64-bit significand field (S1:E15:SIG64), bias 16383
- nf4: QLoRA/bitsandbytes NF4 16-entry quantile table over [-1,1]
- gfternary: 2-bit {-phi, 0, +phi}, exhaustive 4-code enumeration
INDEX totals: bitexact 49->55, structural 34->28, total 83 (unchanged).
README index/counts/SHA-256/changelog regenerated. double_double and
quad_double stay structural (composite multi-double, no single S:E:M).
All packs and generator ASCII-only. Anchor: phi^2 + phi^-2 = 3.
Closes #1076
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PR DashboardGenerated at: 2026-06-14 12:24:00 UTC
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Summary
Promotes 6 conformance packs from structural (placeholder,
bitexact: false) to bit-precise (bitexact: true,abs_error = 0for every recorded vector) by adding dedicated reference codecs toconformance/vectors/gen_all_formats.py. Follows #1070.Codecs added
ibm_hfp32/64/128value = 0.M(2) * 16^(E-64); 3.0 = 0.1875 x 16^1x87_fp80value = (SIG/2^63) * 2^(E-16383)nf4gfternaryNew helpers:
make_ibm_hfp_decoder/ibm_hfp_encode_exact,make_x87_decoder/x87_encode_exact,make_nf4_decoder+NF4_TABLE,make_gfternary_decoder, routed inbuild_decodable/build_bitexact_pack.Result
INDEX_all_formats.json:bitexact_packs49 -> 55,structural_packs34 -> 28,total_packs83 (unchanged).abs_error = 0.gfternaryandnf4honestly record a null anchor (3.0 not a grid point) with a note -- no false claim.double_double/quad_doublestay structural (composite multi-double, no single S:E:M) -- honest, not promoted.README.mdindex, counts, SHA-256 block (all 83 verified), and a changelog entry updated.docs/NOW.mdnewest entry added.Anchor identity: phi^2 + phi^-2 = 3.
Closes #1076