dgb: saturating uint288 emergency-decay shift + proving KAT - #562
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Replace uint256 eased<<=halvings (wraps at 2^256, ~50-68min death-spiral gap vs oracle) with a saturating shift computed in uint288 so emergency decay saturates to MAX, matching frstrtr/p2pool-dgb-scrypt. Adds EmergencyDecaySaturation KAT: h21=57.5min fails-before/passes-after, NEW==ORACLE 0-mismatch + interpolation, death-spiral>0. Consensus-bearing; held for operator scope tap, no self-merge.
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Summary
Fixes a consensus-bearing overflow in the DGB sharechain emergency-decay difficulty path. The "eased" max_bits adjustment shifted in a width that wraps at its modulus during a prolonged share drought, producing a ~50-68 min death-spiral gap where the SUT diverges from the oracle (which saturates to MAX).
Change: perform the emergency-decay shift in uint288 with an explicit saturating clamp to MAX, matching
frstrtr/p2pool-dgb-scryptget_decayed_cumulative_weightsreduction semantics. Verified bit-for-bit equal to the oracle across a full sparse-prev by horizon sweep (5 prev values, h=0..255, plus interpolation points).Scope / fencing
src/impl/dgb/coin/share_tracker.hpp— uint288 incremental saturate in the emergency-decay shift.src/impl/dgb/test/emergency_decay_saturation_test.cpp— new proving KAT (suiteEmergencyDecaySaturation.*, ctest d-miner5(p1): transport-agnostic miner notification engine (evaluator + core + email adapter) #552-555), oracle-pinned, non-circular.src/impl/dgb/test/CMakeLists.txt— wires the new test (full SCC link)..github/workflows/build.yml— addsdgb_emergency_decay_saturation_testto BOTH coin-matrix allowlists so it is built and run, not a NOT_BUILT sentinel.Fenced to
src/impl/dgbplus the new KAT plus CI allowlist. No edits to shared base, ltc, doge, or bitcoin_family.Bucket classification
Bucket-2 (v36-native shared structure): the uint288 saturating-shift semantics here are the reference std for the other Scrypt-family coins. ltc-doge cc'd to confirm reduction-order parity against the oracle thread.
Compat
Backward-compatible with the DGB older baseline during the crossing window; conforms to
frstrtr/p2pool-dgb-scryptoracle. No p2pool-merged-v36 divergence introduced.Verification
EmergencyDecaySaturation.*KAT: oracle-equal across full sweep.