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fix infinite loop in rand(::Range(BigInt)) #8255

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fix infinite loop in rand(::Range(BigInt)) #8255

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cd44752
implement rand(::Range(BigInt)) (previously, it overflowed the stack)
rfourquet Sep 8, 2014
02cb414
re-add BigInt tests from commit bf8c452112
rfourquet Sep 10, 2014
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42 changes: 39 additions & 3 deletions base/random.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -182,6 +182,27 @@ for (T, U) in [(Uint8, Uint32), (Uint16, Uint32),
@eval RandIntGen(r::UnitRange{$T}) = isempty(r) ? error("range must be non-empty") : RandIntGen(first(r), convert($U, last(r) - first(r) + 1)) # overflow ok
end


# generator for BigInt
immutable RandIntGenBigInt
a::BigInt # first
m::BigInt # range length - 1
nlimbs::Int # number of limbs in generated BigInt's
mask::Culong # applied to the highest limb
end

function RandIntGen(r::UnitRange{BigInt})
isempty(r) && error("range must be non-empty")
m = last(r) - first(r)
# mpz_sizeinbase is exact in this case, so this is faster than calling ndigits(m,2)
nd = int(ccall((:__gmpz_sizeinbase,:libgmp), Culong, (Ptr{BigInt}, Int32), &m, 2))
nlimbs, highbits = divrem(nd, 8*sizeof(Culong))
highbits > 0 && (nlimbs += 1)
mask = highbits == 0 ? ~zero(Culong) : one(Culong)<<highbits - one(Culong)
return RandIntGenBigInt(first(r), m, nlimbs, mask)
end


# this function uses 32 bit entropy for small ranges of length <= typemax(Uint32) + 1
# RandIntGen is responsible for providing the right value of k
function rand{T<:Union(Uint64, Int64)}(g::RandIntGen{T,Uint64})
Expand All @@ -208,17 +229,32 @@ function rand{T<:Integer, U<:Unsigned}(g::RandIntGen{T,U})
convert(T, g.a + rem_knuth(x, g.k))
end

rand{T<:Union(Signed,Unsigned,Bool,Char)}(r::UnitRange{T}) = rand(RandIntGen(r))
rand{T}(r::Range{T}) = r[rand(1:(length(r)))]

function rand!(g::RandIntGen, A::AbstractArray)
function rand(g::RandIntGenBigInt)
x = BigInt()
while true
xd = ccall((:__gmpz_limbs_write, :libgmp), Ptr{Culong}, (Ptr{BigInt}, Cint), &x, g.nlimbs)
limbs = pointer_to_array(xd, g.nlimbs)
rand!(limbs)
limbs[end] &= g.mask
ccall((:__gmpz_limbs_finish, :libgmp), Ptr{Culong}, (Ptr{BigInt}, Cint), &x, g.nlimbs)
x <= g.m && break
end
ccall((:__gmpz_add, :libgmp), Void, (Ptr{BigInt}, Ptr{BigInt}, Ptr{BigInt}), &x, &x, &g.a)
return x
end

rand{T<:Union(Signed,Unsigned,BigInt,Bool,Char)}(r::UnitRange{T}) = rand(RandIntGen(r))

function rand!(g::Union(RandIntGen,RandIntGenBigInt), A::AbstractArray)
for i = 1 : length(A)
@inbounds A[i] = rand(g)
end
return A
end

rand!{T<:Union(Signed,Unsigned,Bool,Char)}(r::UnitRange{T}, A::AbstractArray) = rand!(RandIntGen(r), A)
rand!{T<:Union(Signed,Unsigned,BigInt,Bool,Char)}(r::UnitRange{T}, A::AbstractArray) = rand!(RandIntGen(r), A)

function rand!(r::Range, A::AbstractArray)
g = RandIntGen(1:(length(r)))
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16 changes: 15 additions & 1 deletion test/random.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ randn!(MersenneTwister(42), A)
@test A == [-0.5560268761463861 0.027155338009193845;
-0.444383357109696 -0.29948409035891055]

for T in (Int8, Uint8, Int16, Uint16, Int32, Uint32, Int64, Uint64, Int128, Uint128,
for T in (Int8, Uint8, Int16, Uint16, Int32, Uint32, Int64, Uint64, Int128, Uint128, BigInt,
Char, Float16, Float32, Float64, Rational{Int})
r = rand(convert(T, 97):convert(T, 122))
@test typeof(r) == T
Expand All @@ -53,6 +53,20 @@ if sizeof(Int32) < sizeof(Int)

end

# BigInt specific
s = big(typemax(Uint128)-1000):(big(typemax(Uint128)) + 10000)
@test rand(s) != rand(s)
@test big(typemax(Uint128)-1000) <= rand(s) <= big(typemax(Uint128)) + 10000
r = rand(s, 1, 2)
@test size(r) == (1, 2)
@test typeof(r) == Matrix{BigInt}

srand(0)
r = rand(s)
srand(0)
@test rand(s) == r


randn(100000)
randn!(Array(Float64, 100000))
randn(MersenneTwister(10), 100000)
Expand Down