Median Block Selection for DAA now follows ABC algorithm. #12
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The median Block selection algorithm for the Difficulty Adjustment Algorithm now follows the expanded footprints specified in the specification.
The median selection algorithm previously used a descending order stable sort algorithm via a custom Comparitor on the Block's Timestamp. This operation is inconsistent with ABC's implementation when 2 of the 3 Blocks have the same Timestamp value, which causes the node to select a different median Block with a different ChainWork value, ultimately hypothetically leading to a different difficulty calculation.
This implementation difference was never encountered on main net. Although the likeliness of encountering this edge case is rare, all nodes should upgrade to the next release containing this patch as it would result in a chain split if encountered.
This bug fix is in response to Issue #11 . His commentary is located in more depth here: https://read.cash/@Fernando/on-daa-implementation-algorithms-and-specifications-b739e631