Skip to content

Round without overflow (Fix #59) #64

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

Merged
merged 1 commit into from
Mar 27, 2018
Merged

Round without overflow (Fix #59) #64

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
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
31 changes: 19 additions & 12 deletions src/DecFP.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -150,15 +150,20 @@ for w in (32,64,128)

$BID(x::AbstractString) = parse($BID, x)

function tostring(x::$BID)
# fills global _buffer
ccall(($(bidsym(w,"to_string")), libbid), Cvoid, (Ptr{UInt8}, $BID), _buffer, x)
end

function Base.show(io::IO, x::$BID)
isnan(x) && (write(io, "NaN"); return)
isinf(x) && (write(io, signbit(x) ? "-Inf" : "Inf"); return)
x == 0 && (write(io, signbit(x) ? "-0.0" : "0.0"); return)
ccall(($(bidsym(w,"to_string")), libbid), Cvoid, (Ptr{UInt8}, $BID), _buffer, x)
tostring(x)
if _buffer[1] == UInt8('-')
write(io, '-')
end
normalized_exponent = nox(ccall(($(bidsym(w,"ilogb")), libbid), Cint, ($BID,), x))
normalized_exponent = exponent10(x)
lastdigitindex = Compat.findfirst(equalto(UInt8('E')), _buffer) - 1
lastnonzeroindex = Compat.findlast(!equalto(UInt8('0')), view(_buffer, 1:lastdigitindex))
if -5 < normalized_exponent < 6
Expand Down Expand Up @@ -210,13 +215,12 @@ for w in (32,64,128)
if n > length(DIGITS) - 1
n = length(DIGITS) - 1
end
# rounded = round(x * exp10($BID(n)), RoundNearestTiesAway)
rounded = @xchk(ccall(($(bidsym(w,"round_integral_nearest_away")), libbid), $BID, ($BID,), x * exp10($BID(n))), InexactError, :round, $BID, x, mask=INVALID | OVERFLOW)
rounded = round(ldexp10(x, n), RoundNearestTiesAway)
if rounded == 0
DIGITS[1] = UInt8('0')
return Int32(1), Int32(1), signbit(x)
end
ccall(($(bidsym(w,"to_string")), libbid), Cvoid, (Ptr{UInt8}, $BID), _buffer, rounded)
tostring(rounded)
trailing_zeros = 0
i = 2
while _buffer[i] != UInt8('E')
Expand Down Expand Up @@ -258,16 +262,19 @@ for w in (32,64,128)
end
return Int32(1), Int32(1), signbit(x)
end
normalized_exponent = nox(ccall(($(bidsym(w,"ilogb")), libbid), Cint, ($BID,), x))
# rounded = round(x * exp10($BID(n - 1 - normalized_exponent)), RoundNearestTiesAway)
rounded = @xchk(ccall(($(bidsym(w,"round_integral_nearest_away")), libbid), $BID, ($BID,), x * exp10($BID(n - 1 - normalized_exponent))), InexactError, :round, $BID, x, mask=INVALID | OVERFLOW)
rounded_exponent = nox(ccall(($(bidsym(w,"ilogb")), libbid), Cint, ($BID,), rounded))
ccall(($(bidsym(w,"to_string")), libbid), Cvoid, (Ptr{UInt8}, $BID), _buffer, rounded)
normalized_exponent = exponent10(x)
rounded = round(ldexp10(x, n - 1 - normalized_exponent), RoundNearestTiesAway)
rounded_exponent = exponent10(rounded)
tostring(rounded)
i = 2
while _buffer[i] != UInt8('E')
DIGITS[i - 1] = _buffer[i]
i += 1
end
while i <= n + 1
DIGITS[i - 1] = UInt8('0')
i += 1
end
pt = normalized_exponent + rounded_exponent - n + 2
neg = signbit(x)
return Int32(n), Int32(pt), neg
Expand All @@ -287,8 +294,8 @@ for w in (32,64,128)
Base.eps(x::$BID) = ifelse(isfinite(x), @xchk(nextfloat(x) - x, OverflowError, "$($BID) value overflow", mask=OVERFLOW), $(_parse(T, "NaN")))

# the meaning of the exponent is different than for binary FP: it is 10^n, not 2^n:
# Base.exponent(x::$BID) = nox(ccall(($(bidsym(w,"ilogb")), libbid), Cint, ($BID,), x))
# Base.ldexp(x::$BID, n::Integer) = nox(ccall(($(bidsym(w,"ldexp")), libbid), $BID, ($BID,Cint), x, n))
exponent10(x::$BID) = nox(ccall(($(bidsym(w,"ilogb")), libbid), Cint, ($BID,), x))
ldexp10(x::$BID, n::Integer) = nox(ccall(($(bidsym(w,"ldexp")), libbid), $BID, ($BID,Cint), x, n))
Copy link
Member

@stevengj stevengj Mar 26, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should these be exported?

Copy link
Member

@stevengj stevengj Mar 26, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Maybe in a separate PR.

Copy link
Collaborator Author

@jmkuhn jmkuhn Mar 26, 2018

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

OK. I'll export these in a separate PR.

end

for (f,c) in ((:isnan,"isNaN"), (:isinf,"isInf"), (:isfinite,"isFinite"), (:issubnormal,"isSubnormal"))
Expand Down
4 changes: 2 additions & 2 deletions test/runtests.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -195,8 +195,8 @@ for T in (Dec32, Dec64, Dec128)
@test_throws DomainError sqrt(yd)
@test_throws DomainError acosh(zd)

# @test ldexp(parse(T, "1"), 3) == 1000
# @test exponent(parse(T, "1000")) == 3
@test DecFP.ldexp10(parse(T, "1"), 3) == 1000
@test DecFP.exponent10(parse(T, "1000")) == 3
@test sqrt(complex(yd)) ≈ sqrt(complex(y))

@test typeof(xd * pi) == T
Expand Down