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seed Dict so that hashes get non-zero h #57277

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seed Dict so that hashes get non-zero h #57277

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24 changes: 14 additions & 10 deletions base/dict.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -70,21 +70,22 @@ mutable struct Dict{K,V} <: AbstractDict{K,V}
ndel::Int
count::Int
age::UInt
seed::UInt
idxfloor::Int # an index <= the indices of all used slots
maxprobe::Int

function Dict{K,V}() where V where K
n = 0
slots = Memory{UInt8}(undef,n)
fill!(slots, 0x0)
new(slots, Memory{K}(undef, n), Memory{V}(undef, n), 0, 0, 0, max(1, n), 0)
new(slots, Memory{K}(undef, n), Memory{V}(undef, n), 0, 0, 0, rand(UInt), max(1, n), 0)
end
function Dict{K,V}(d::Dict{K,V}) where V where K
new(copy(d.slots), copy(d.keys), copy(d.vals), d.ndel, d.count, d.age,
d.idxfloor, d.maxprobe)
rand(UInt), d.idxfloor, d.maxprobe)
end
function Dict{K, V}(slots::Memory{UInt8}, keys::Memory{K}, vals::Memory{V}, ndel::Int, count::Int, age::UInt, idxfloor::Int, maxprobe::Int) where {K, V}
new(slots, keys, vals, ndel, count, age, idxfloor, maxprobe)
new(slots, keys, vals, ndel, count, age, rand(UInt), idxfloor, maxprobe)
end
end
function Dict{K,V}(kv) where V where K
Expand Down Expand Up @@ -121,11 +122,12 @@ empty(a::AbstractDict, ::Type{K}, ::Type{V}) where {K, V} = Dict{K, V}()
# Gets 7 most significant bits from the hash (hsh), first bit is 1
_shorthash7(hsh::UInt) = (hsh >> (8sizeof(UInt)-7))%UInt8 | 0x80

# hashindex (key, sz) - computes optimal position and shorthash7
# hashindex (key, h, sz) - computes optimal position and shorthash7
# idx - optimal position in the hash table
# seed::UInt - seed value of the dictionary (to prevent random collisions)
# sh::UInt8 - short hash (7 highest hash bits)
function hashindex(key, sz)
hsh = hash(key)::UInt
function hashindex(key, seed, sz)
hsh = hash(key, seed)::UInt
idx = (((hsh % Int) & (sz-1)) + 1)::Int
return idx, _shorthash7(hsh)
end
Expand All @@ -142,6 +144,7 @@ end
newsz = _tablesz(newsz)
h.age += 1
h.idxfloor = 1
h.seed = rand(UInt)
if h.count == 0
# TODO: tryresize
h.slots = Memory{UInt8}(undef, newsz)
Expand All @@ -158,14 +161,15 @@ end
keys = Memory{K}(undef, newsz)
vals = Memory{V}(undef, newsz)
age0 = h.age
seed = h.seed
count = 0
maxprobe = 0

for i = 1:sz
@inbounds if (olds[i] & 0x80) != 0
k = oldk[i]
v = oldv[i]
index, sh = hashindex(k, newsz)
index, sh = hashindex(k, seed, newsz)
index0 = index
while slots[index] != 0
index = (index & (newsz-1)) + 1
Expand Down Expand Up @@ -239,7 +243,7 @@ function ht_keyindex(h::Dict{K,V}, key) where V where K
iter = 0
maxprobe = h.maxprobe
maxprobe < sz || throw(AssertionError()) # This error will never trigger, but is needed for terminates_locally to be valid
index, sh = hashindex(key, sz)
index, sh = hashindex(key, h.seed, sz)
keys = h.keys

@assume_effects :terminates_locally :noub @inbounds while true
Expand All @@ -266,12 +270,12 @@ function ht_keyindex2_shorthash!(h::Dict{K,V}, key) where V where K
sz = length(h.keys)
if sz == 0 # if Dict was empty resize and then return location to insert
rehash!(h, 4)
index, sh = hashindex(key, length(h.keys))
index, sh = hashindex(key, h.seed, length(h.keys))
return -index, sh
end
iter = 0
maxprobe = h.maxprobe
index, sh = hashindex(key, sz)
index, sh = hashindex(key, h.seed, sz)
avail = 0
keys = h.keys

Expand Down
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