Skip to content

Fix computation of range length in certain cases (fix #20373) #20377

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 2 commits into from
Feb 8, 2017
Merged

Fix computation of range length in certain cases (fix #20373) #20377

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
6eca1df
Fix computation of range length in certain cases (fix #20373)
StefanKarpinski Feb 1, 2017
458f9e8
linspace construction fails on 32-bit systems
StefanKarpinski Feb 7, 2017
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
5 changes: 3 additions & 2 deletions base/twiceprecision.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -122,8 +122,6 @@ end

function colon{T<:Union{Float16,Float32,Float64}}(start::T, step::T, stop::T)
step == 0 && throw(ArgumentError("range step cannot be zero"))
len = max(0, floor(Int, (stop-start)/step) + 1)
# Because len might be too small by 1 due to roundoff error, let's
# see if the inputs have exact rational approximations (and if so,
# perform all computations in terms of the rationals)
step_n, step_d = rat(step)
Expand All @@ -149,6 +147,9 @@ function colon{T<:Union{Float16,Float32,Float64}}(start::T, step::T, stop::T)
end
end
# Fallback, taking start and step literally
len = max(0, floor(Int, (stop-start)/step) + 1)
stop′ = start + len*step
len += (start < stop′ <= stop) + (start > stop′ >= stop)
StepRangeLen(TwicePrecision(start, zero(T)), twiceprecision(step, nbitslen(T, len, 1)), len)
end

Expand Down
23 changes: 23 additions & 0 deletions test/ranges.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -333,6 +333,29 @@ for T = (Float32, Float64,),# BigFloat),
@test [r[n:-2:1];] == [r;][n:-2:1]
end

# issue #20373 (unliftable ranges with exact end points)
@test [3*0.05:0.05:0.2;] == [linspace(3*0.05,0.2,2);] == [3*0.05,0.2]
@test [0.2:-0.05:3*0.05;] == [linspace(0.2,3*0.05,2);] == [0.2,3*0.05]
@test [-3*0.05:-0.05:-0.2;] == [linspace(-3*0.05,-0.2,2);] == [-3*0.05,-0.2]
@test [-0.2:0.05:-3*0.05;] == [linspace(-0.2,-3*0.05,2);] == [-0.2,-3*0.05]

for T = (Float32, Float64,), i = 1:2^15, n = 1:5
start, step = randn(T), randn(T)
stop = start + (n-1)*step
r = start:step:stop
@test n == length(r)
# FIXME: these fail some small portion of the time
@test_skip start == first(r)
@test_skip stop == last(r)
# FIXME: linspace construction fails on 32-bit
Sys.WORD_SIZE == 64 || continue
l = linspace(start,stop,n)
@test n == length(l)
# FIXME: these fail some small portion of the time
@test_skip start == first(l)
@test_skip stop == last(l)
end

# linspace & ranges with very small endpoints
for T = (Float32, Float64)
z = zero(T)
Expand Down