I want this as fast as possible, so it can be added to code paths without
slowing them down.
Avoid the set lookup, and rely on laziness,
drops runtime from 14.37 ns to 11.03 ns according to this criterion benchmark:
import Criterion.Main
import qualified Types.Difference as New
import qualified Types.DifferenceOld as Old
main :: IO ()
main = defaultMain
[ bgroup "hasDifference"
[ bench "new" $ whnf (New.hasDifference New.OneLevelObjectHash) new
, bench "old" $ whnf (Old.hasDifference Old.OneLevelObjectHash) old
]
]
where
s = "fromList [ObjectHashLower, OneLevelObjectHash, OneLevelBranchHash]"
new = New.readDifferences s
old = Old.readDifferences s
A little bit of added boilerplate, but I suppose it's worth it to not
need to worry about set lookup overhead. Note that adding more differences
would slow down the old implementation; the new implementation will run
the same speed.
Eliminated complexity and future proofed. The most important change is that
all functions over Difference are now total; any Difference that can be
expressed should be handled. Avoids needs for sanity checking of inputs,
and version skew with the future.
Also, the difference.log now serializes a [Difference], not a Differences.
This saves space and keeps it simpler.
Note that [Difference] might contain conflicting differences (eg,
[Version5, Version6]. In this case, one of them needs to consistently win
over the others, probably based on Ord.
* init: Repository tuning parameters can now be passed when initializing a
repository for the first time. For details, see
http://git-annex.branchable.com/tuning/
* merge: Refuse to merge changes from a git-annex branch of a repo
that has been tuned in incompatable ways.
