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reduce allocations for string(::IEEEFloat) #57977

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reduce allocations for string(::IEEEFloat) #57977

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0298f15
reduce allocations for string(::IEEEFloat)
oscardssmith Apr 1, 2025
85a3702
further reduce used memory
oscardssmith Apr 2, 2025
5354cfd
reduce allocation
oscardssmith Apr 2, 2025
b378ad7
fix constants
oscardssmith Apr 6, 2025
6176380
add tests
oscardssmith Apr 22, 2025
a03f845
typo
oscardssmith Apr 24, 2025
06287cb
fix test
oscardssmith Apr 24, 2025
0b6470c
fix
oscardssmith Apr 24, 2025
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15 changes: 12 additions & 3 deletions base/ryu/Ryu.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,15 @@ neededdigits(::Type{Float64}) = 309 + 17
neededdigits(::Type{Float32}) = 39 + 9 + 2
neededdigits(::Type{Float16}) = 9 + 5 + 9

"""
Ryu.neededfloatdigits(T)

Number of digits necessary to represent type `T` in shortest precision.
"""
neededfloatdigits(::Type{Float64}) = 24
neededfloatdigits(::Type{Float32}) = 15
neededfloatdigits(::Type{Float16}) = 20

"""
Ryu.writeshortest(x, plus=false, space=false, hash=true, precision=-1, expchar=UInt8('e'), padexp=false, decchar=UInt8('.'), typed=false, compact=false)
Ryu.writeshortest(buf::AbstractVector{UInt8}, pos::Int, x, args...)
Expand Down Expand Up @@ -111,16 +120,16 @@ end

function Base.show(io::IO, x::T, forceuntyped::Bool=false, fromprint::Bool=false) where {T <: Base.IEEEFloat}
compact = get(io, :compact, false)::Bool
buf = Base.StringVector(neededdigits(T))
buf = Memory{UInt8}(undef, neededfloatdigits(T))
typed = !forceuntyped && !compact && Base.nonnothing_nonmissing_typeinfo(io) !== typeof(x)
pos = writeshortest(buf, 1, x, false, false, true, -1,
(x isa Float32 && !fromprint) ? UInt8('f') : UInt8('e'), false, UInt8('.'), typed, compact)
write(io, resize!(buf, pos - 1))
write(io, view(buf, 1:pos - 1))
return
end

function Base.string(x::T) where {T <: Base.IEEEFloat}
buf = Base.StringVector(neededdigits(T))
buf = Base.StringVector(neededfloatdigits(T))
pos = writeshortest(buf, 1, x, false, false, true, -1,
UInt8('e'), false, UInt8('.'), false, false)
return String(resize!(buf, pos - 1))
Expand Down
7 changes: 7 additions & 0 deletions test/ryu.jl
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Expand Up @@ -122,18 +122,21 @@ end
# 64-bit opt-size=0: 52 <= dist <= 52
# 64-bit opt-size=1: 52 <= dist <= 59
@test "2.900835519859558e-216" == Ryu.writeshortest(todouble(false, 307, 0))
@test "-2.900835519859558e-216" == Ryu.writeshortest(todouble(true, 307, 0))
# 32-bit opt-size=0: 51 <= dist <= 51
# 32-bit opt-size=1: 51 <= dist <= 59
# 64-bit opt-size=0: 52 <= dist <= 52
# 64-bit opt-size=1: 52 <= dist <= 59
@test "5.801671039719115e-216" == Ryu.writeshortest(todouble(false, 306, maxMantissa))
@test "-5.801671039719115e-216" == Ryu.writeshortest(todouble(true, 306, maxMantissa))

# https:#github.com/ulfjack/ryu/commit/19e44d16d80236f5de25800f56d82606d1be00b9#commitcomment-30146483
# 32-bit opt-size=0: 49 <= dist <= 49
# 32-bit opt-size=1: 44 <= dist <= 49
# 64-bit opt-size=0: 50 <= dist <= 50
# 64-bit opt-size=1: 44 <= dist <= 50
@test "3.196104012172126e-27" == Ryu.writeshortest(todouble(false, 934, 0x000FA7161A4D6E0C))
@test "-3.196104012172126e-27" == Ryu.writeshortest(todouble(true, 934, 0x000FA7161A4D6E0C))
end

@testset "SmallIntegers" begin
Expand Down Expand Up @@ -304,6 +307,7 @@ end
@test "1.00014165e-36" == Ryu.writeshortest(1.00014165f-36)
@test "200.0" == Ryu.writeshortest(200f0)
@test "3.3554432e7" == Ryu.writeshortest(3.3554432f7)
@test "-1.00000075e-36" == Ryu.writeshortest(-1.00000075f-36) #longest Float32
end

@testset "LooksLikePow5" begin
Expand Down Expand Up @@ -368,6 +372,9 @@ end
# return fails / (fails + success)
# end

@testset "Regression" begin
@test "-0.00010014" == Ryu.writeshortest(Float16(-0.00010014)) #longest Float16
end
end # Float16

@testset "writeshortest(::AbstractVector, pos, ...)" begin
Expand Down