FA-72104 / Error-correcting codes / Member archive

Min-sum offset can flip the message sign · case 04

Weak messages flip sign after the offset is applied.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Offset min-sum check-node update for LDPC decoding with integer LLRs. For each edge i the outgoing message is the product of the signs of all OTHER incoming LLRs (0 counts as positive) times max(min |other LLR| - beta, 0). Fewer than two edges returns None. Return the outgoing messages in edge order.

Why this case matters

LDPC decoders in Wi-Fi, 5G and SSD controllers run this update billions of times per second.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression [[12, 0, -10, 8], 1]	`[1, -7, -1, 1]`	`[0, -7, 0, 0]`	Failed

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