Improve speed of hypdiff for large text #5
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- `Hash` knows how to initialize values of missing keys. - `NodeMap` returns the map and is not (anymore) called with a block.
The loop's condition is sufficient. The artifact is from a spike which tried to identify a "common tail" of insertions and deletions.
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Any update on this? See https://github.com/infopark/scrivito_cms/blob/master/app/static/hyp_diff_patches.rb ;-) |
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If large text is diffed,
Diff::LCSreceives a lot of "single whitespace" sequence tokens, which have a heavy impact on execution time. The effect is not linear with the number of whitespaces, but more likeO(n^2).The solution is to hide (most) whitespace sequence items from
Diff::LCS. A whitespaceTextFromNodeis now "merged" into its successorTextFromNodeif both belong to the same XML Text Node (i.e. originate from the samesplit).This helps
Diff::LCSin two ways:<and alikeNote that specs are kept happy by collapsing adjacent whitespaces nodes (even across text nodes) first, and only afterwards merge a whitespace token into its successor.