Skip to content

Tests: Reverse bits during key generation #508

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Draft
wants to merge 1 commit into
base: master
Choose a base branch
from
Draft

Tests: Reverse bits during key generation #508

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
11 changes: 9 additions & 2 deletions tests/Util/Key.hs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,12 +1,14 @@
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE TypeApplications #-}

module Util.Key (Key(..), keyToInt, incKey, collisionAtHash) where

import Data.Bits (bit, (.&.))
import Data.Hashable (Hashable (hashWithSalt))
import Data.Word (Word16)
import GHC.Exts (Int (..), bitReverse#, int2Word#, word2Int#)
import GHC.Generics (Generic)
import Test.QuickCheck (Arbitrary (..), CoArbitrary (..), Function, Gen, Large)

Expand Down Expand Up @@ -51,8 +53,8 @@ arbitraryHash = do
, (1, QC.elements [-1, 0xFF, 0xFFF])
]
i <- QC.frequency gens
moreCollisions' <- QC.elements [moreCollisions, id]
pure (moreCollisions' i)
transform <- QC.elements [id, moreCollisions, bitReverse]
pure (transform i)

-- | Mask out most bits to produce more collisions
moreCollisions :: Int -> Int
Expand All @@ -62,6 +64,11 @@ moreCollisions w = fromIntegral (w .&. moreCollisionsMask)
moreCollisionsMask :: Int
moreCollisionsMask = sum [bit n | n <- [0, 3, 8, 14, 61]]

-- | Reverse order of bits, in order to generate variation in the
-- high bits, resulting in HashMap trees of greater height.
bitReverse :: Int -> Int
bitReverse (I# i) = I# (word2Int# (bitReverse# (int2Word# i)))

keyToInt :: Key -> Int
keyToInt (K h x) = h * fromEnum x

Expand Down