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faster digits(::BigInt) #37075

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merged 14 commits into from
Aug 18, 2020
Merged

faster digits(::BigInt) #37075

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61f35da
faster digits(::BigInt)
stevengj Aug 17, 2020
e365914
correctness for base > 10
stevengj Aug 17, 2020
802c7cf
simplify
stevengj Aug 17, 2020
bf7a878
fixes
stevengj Aug 17, 2020
9443189
better error for base < 2
stevengj Aug 17, 2020
4ccaeba
add a test
stevengj Aug 17, 2020
496568d
indent 4
stevengj Aug 17, 2020
0fb9919
digits -> digits!
stevengj Aug 17, 2020
76a86fb
support offset arrays
stevengj Aug 17, 2020
f9eee69
fix negative numbers, padding
stevengj Aug 17, 2020
58e95e1
Update gmp.jl
stevengj Aug 17, 2020
ed4b9b0
more tests
stevengj Aug 17, 2020
f259867
typo
stevengj Aug 17, 2020
7f64c01
another typo
stevengj Aug 17, 2020
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20 changes: 19 additions & 1 deletion base/gmp.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,7 @@ import .Base: *, +, -, /, <, <<, >>, >>>, <=, ==, >, >=, ^, (~), (&), (|), xor,
sum, trailing_zeros, trailing_ones, count_ones, tryparse_internal,
bin, oct, dec, hex, isequal, invmod, _prevpow2, _nextpow2, ndigits0zpb,
widen, signed, unsafe_trunc, trunc, iszero, isone, big, flipsign, signbit,
sign, hastypemax, isodd
sign, hastypemax, isodd, digits!

if Clong == Int32
const ClongMax = Union{Int8, Int16, Int32}
Expand Down Expand Up @@ -694,6 +694,24 @@ function string(n::BigInt; base::Integer = 10, pad::Integer = 1)
String(sv)
end

function digits!(a::AbstractVector{T}, n::BigInt; base::Integer = 10) where {T<:Integer}
if 2 ≤ base ≤ 62
s = codeunits(string(n; base))
i, j = firstindex(a)-1, length(s)+1
lasti = min(lastindex(a), firstindex(a) + length(s)-1 - isneg(n))
while i < lasti
# base ≤ 36: 0-9, plus a-z for 10-35
# base > 36: 0-9, plus A-Z for 10-35 and a-z for 36..61
x = s[j -= 1]
a[i += 1] = base ≤ 36 ? (x>0x39 ? x-0x57 : x-0x30) : (x>0x39 ? (x>0x60 ? x-0x3d : x-0x37) : x-0x30)
end
lasti = lastindex(a)
while i < lasti; a[i+=1] = zero(T); end
return isneg(n) ? map!(-,a,a) : a
end
return invoke(digits!, Tuple{typeof(a), Integer}, a, n; base) # slow generic fallback
end

function ndigits0zpb(x::BigInt, b::Integer)
b < 2 && throw(DomainError(b, "`b` cannot be less than 2."))
x.size == 0 && return 0 # for consistency with other ndigits0z methods
Expand Down
10 changes: 10 additions & 0 deletions test/gmp.jl
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Expand Up @@ -293,6 +293,16 @@ let s, n = bigfib(1000001)
@test startswith(s, "316047687386689")
end

@testset "digits" begin
n = Int64(2080310129088201558)
N = big(n)
for base in (2,7,10,11,16,30,50,62,64,100), pad in (0,1,10,100)
@test digits(n; base, pad) == digits(N; base, pad)
@test digits(-n; base, pad) == digits(-N; base, pad)
@test digits!(Vector{Int}(undef, pad), n; base) == digits!(Vector{Int}(undef, pad), N; base)
end
end

# serialization (#5133)
let n = parse(BigInt, "359334085968622831041960188598043661065388726959079837"),
b = IOBuffer()
Expand Down