Skip to content
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

Add with_overflow for add, sub, and mul #102

Merged
merged 5 commits into from
Jan 16, 2025
Merged

Add with_overflow for add, sub, and mul #102

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
2e71f3e
Fix ambiguities.
mbarbar Jan 16, 2025
2297c6f
Add tests.
mbarbar Jan 16, 2025
48cc31a
Merge remote-tracking branch 'upstream/master'
mbarbar Jan 16, 2025
c7e0826
Comment
mbarbar Jan 16, 2025
112d5e0
Simplify logic.
mbarbar Jan 16, 2025
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
42 changes: 33 additions & 9 deletions src/FixedPointDecimals.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -397,6 +397,32 @@ end

# --- Checked arithmetic ---

function Base.add_with_overflow(x::T, y::T) where {T<:FD}
z, b = Base.add_with_overflow(x.i, y.i)
return (reinterpret(T, z), b)
end
Base.Checked.add_with_overflow(x::FD, y::FD) = Base.Checked.add_with_overflow(promote(x, y)...)
Base.Checked.add_with_overflow(x::FD, y) = Base.Checked.add_with_overflow(promote(x, y)...)
Base.Checked.add_with_overflow(x, y::FD) = Base.Checked.add_with_overflow(promote(x, y)...)

function Base.sub_with_overflow(x::T, y::T) where {T<:FD}
z, b = Base.sub_with_overflow(x.i, y.i)
return (reinterpret(T, z), b)
end
Base.Checked.sub_with_overflow(x::FD, y::FD) = Base.Checked.sub_with_overflow(promote(x, y)...)
Base.Checked.sub_with_overflow(x::FD, y) = Base.Checked.sub_with_overflow(promote(x, y)...)
Base.Checked.sub_with_overflow(x, y::FD) = Base.Checked.sub_with_overflow(promote(x, y)...)

function Base.Checked.mul_with_overflow(x::FD{T,f}, y::FD{T,f}) where {T<:Integer,f}
powt = coefficient(FD{T, f})
quotient, remainder = fldmodinline(_widemul(x.i, y.i), powt)
v = _round_to_nearest(quotient, remainder, powt)
return (reinterpret(FD{T,f}, Base.trunc_int(T, v)), v < typemin(T) || v > typemax(T))
end
Base.Checked.mul_with_overflow(x::FD, y::FD) = Base.Checked.mul_with_overflow(promote(x, y)...)
Base.Checked.mul_with_overflow(x::FD, y) = Base.Checked.mul_with_overflow(promote(x, y)...)
Base.Checked.mul_with_overflow(x, y::FD) = Base.Checked.mul_with_overflow(promote(x, y)...)

Base.checked_add(x::FD, y::FD) = Base.checked_add(promote(x, y)...)
Base.checked_sub(x::FD, y::FD) = Base.checked_sub(promote(x, y)...)
Base.checked_mul(x::FD, y::FD) = Base.checked_mul(promote(x, y)...)
Expand Down Expand Up @@ -424,21 +450,19 @@ Base.checked_mod(x::FD, y) = Base.checked_mod(promote(x, y)...)
Base.checked_mod(x, y::FD) = Base.checked_mod(promote(x, y)...)

function Base.checked_add(x::T, y::T) where {T<:FD}
z, b = Base.add_with_overflow(x.i, y.i)
z, b = Base.Checked.add_with_overflow(x, y)
b && Base.Checked.throw_overflowerr_binaryop(:+, x, y)
return reinterpret(T, z)
return z
end
function Base.checked_sub(x::T, y::T) where {T<:FD}
z, b = Base.sub_with_overflow(x.i, y.i)
z, b = Base.Checked.sub_with_overflow(x, y)
b && Base.Checked.throw_overflowerr_binaryop(:-, x, y)
return reinterpret(T, z)
return z
end
function Base.checked_mul(x::FD{T,f}, y::FD{T,f}) where {T<:Integer,f}
powt = coefficient(FD{T, f})
quotient, remainder = fldmodinline(_widemul(x.i, y.i), powt)
v = _round_to_nearest(quotient, remainder, powt)
typemin(T) <= v <= typemax(T) || Base.Checked.throw_overflowerr_binaryop(:*, x, y)
return reinterpret(FD{T, f}, T(v))
z, b = Base.Checked.mul_with_overflow(x, y)
b && Base.Checked.throw_overflowerr_binaryop(:*, x, y)
return z
end
# Checked division functions
for divfn in [:div, :fld, :cld]
Expand Down
76 changes: 76 additions & 0 deletions test/FixedDecimal.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -776,6 +776,82 @@ end
@test FD{Int8,1}(2) / Int8(20) == FD{Int8,1}(0.1)
end

@testset "limits: with_overflow math" begin
# Easy to reason about cases of overflow:
@test Base.Checked.add_with_overflow(FD{Int8,2}(1), FD{Int8,2}(1)) == (FD{Int8,2}(-0.56), true)
@test Base.Checked.add_with_overflow(FD{Int8,2}(1), 1) == (FD{Int8,2}(-0.56), true)
@test Base.Checked.add_with_overflow(FD{Int8,2}(1), FD{Int8,2}(0.4)) == (FD{Int8,2}(-1.16), true)

@test Base.Checked.sub_with_overflow(FD{Int8,2}(1), FD{Int8,2}(-1)) == (FD{Int8,2}(-0.56), true)
@test Base.Checked.sub_with_overflow(1, FD{Int8,2}(-1)) == (FD{Int8,2}(-0.56), true)
@test Base.Checked.sub_with_overflow(FD{Int8,2}(-1), FD{Int8,2}(0.4)) == (FD{Int8,2}(1.16), true)

@test Base.Checked.mul_with_overflow(FD{Int8,2}(1.2), FD{Int8,2}(1.2)) == (FD{Int8,2}(-1.12), true)
@test Base.Checked.mul_with_overflow(FD{Int8,1}(12), 2) == (FD{Int8,1}(-1.6), true)
@test Base.Checked.mul_with_overflow(FD{Int8,0}(120), 2) == (FD{Int8,0}(-16), true)
@test Base.Checked.mul_with_overflow(120, FD{Int8,0}(2)) == (FD{Int8,0}(-16), true)

@testset "with_overflow math corner cases" begin
@testset for I in (Int128, UInt128, Int8, UInt8), f in (0,2)
T = FD{I, f}
issigned(I) = signed(I) === I

@test Base.Checked.add_with_overflow(typemax(T), eps(T)) == (typemax(T) + eps(T), true)
issigned(I) && @test Base.Checked.add_with_overflow(typemin(T), -eps(T)) == (typemin(T) + -eps(T), true)
@test Base.Checked.add_with_overflow(typemax(T), 1) == (typemax(T) + 1, true)
@test Base.Checked.add_with_overflow(1, typemax(T)) == (typemax(T) + 1, true)

@test Base.Checked.sub_with_overflow(typemin(T), eps(T)) == (typemin(T) - eps(T), true)
issigned(I) && @test Base.Checked.sub_with_overflow(typemax(T), -eps(T)) == (typemax(T) - -eps(T), true)
@test Base.Checked.sub_with_overflow(typemin(T), 1) == (typemin(T) - 1, true)
if issigned(I) && 2.0 <= typemax(T)
@test Base.Checked.sub_with_overflow(-2, typemax(T)) == (-2 -typemax(T), true)
end

@test Base.Checked.mul_with_overflow(typemax(T), typemax(T)) == (typemax(T) * typemax(T), true)
issigned(I) && @test Base.Checked.mul_with_overflow(typemin(T), typemax(T)) == (typemin(T) * typemax(T), true)
if 2.0 <= typemax(T)
@test Base.Checked.mul_with_overflow(typemax(T), 2) == (typemax(T) * 2, true)
@test Base.Checked.mul_with_overflow(2, typemax(T)) == (2 * typemax(T), true)
issigned(I) && @test Base.Checked.mul_with_overflow(typemin(T), 2) == (typemin(T) * 2, true)
issigned(I) && @test Base.Checked.mul_with_overflow(2, typemin(T)) == (2 * typemin(T), true)
end
end
end

@testset "with_overflow math promotions" begin
x = FD{Int8,1}(1)
y = FD{Int64,1}(2)
@testset for op in (
Base.Checked.add_with_overflow, Base.Checked.sub_with_overflow,
Base.Checked.mul_with_overflow,
)
@test op(x, y) === op(FD{Int64,1}(1), y)
@test op(y, x) === op(y, FD{Int64,1}(1))

@test op(x, 2) === op(x, FD{Int8,1}(2))
@test op(2, x) === op(FD{Int8,1}(2), x)
end
end

@testset "non-overflowing with_overflow math" begin
@test Base.Checked.add_with_overflow(1, FD{Int8,1}(1.1)) == (FD{Int8,1}(2.1), false)
@test Base.Checked.add_with_overflow(FD{Int8,1}(1.1), 1) == (FD{Int8,1}(2.1), false)
@test Base.Checked.add_with_overflow(FD{Int64,8}(30.123), FD{Int64,8}(30)) == (FD{Int64,8}(60.123), false)
@test Base.Checked.add_with_overflow(FD{Int64,8}(30.123), FD{Int64,5}(30)) == (FD{Int64,8}(60.123), false)

@test Base.Checked.sub_with_overflow(3, FD{Int16,2}(2.5)) == (FD{Int16,1}(0.5), false)
@test Base.Checked.sub_with_overflow(FD{Int16,2}(2.5), 3) == (FD{Int16,1}(-0.5), false)
@test Base.Checked.sub_with_overflow(FD{Int32,4}(10.11), FD{Int32,4}(2)) == (FD{Int32,4}(8.11), false)
@test Base.Checked.sub_with_overflow(FD{Int32,4}(10.11), FD{Int32,3}(2)) == (FD{Int32,4}(8.11), false)

@test Base.Checked.mul_with_overflow(4, FD{Int64,6}(2.22)) == (FD{Int64,6}(8.88), false)
@test Base.Checked.mul_with_overflow(FD{Int64,6}(2.22), 4) == (FD{Int64,6}(8.88), false)
@test Base.Checked.mul_with_overflow(FD{Int128,14}(10), FD{Int128,14}(20.1)) == (FD{Int128,14}(201), false)
@test Base.Checked.mul_with_overflow(FD{Int128,30}(10.11), FD{Int128,0}(1)) == (FD{Int128,30}(10.11), false)
end
end

@testset "limits: overflow checked math" begin
# Easy to reason about cases of overflow:
@test_throws OverflowError Base.checked_add(FD{Int8,2}(1), FD{Int8,2}(1))
Expand Down
Loading