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Add sincosd function #30134

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Aug 9, 2019
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Add sincosd function #30134

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06773a0
Add sincosd function
ronisbr Nov 22, 2018
8905370
Apply suggestions from code review
oxinabox Nov 25, 2018
5d8aa1d
Remove @inline annotation from sincosd
ronisbr Apr 13, 2019
38ef1a3
Add compat annotation for sincosd
ronisbr May 28, 2019
5f20cbe
Add NEWS for sincosd
ronisbr May 28, 2019
c7b7d4e
Merge branch 'master' into sincosd
StefanKarpinski Jun 27, 2019
81632d5
Update NEWS.md
ronisbr Aug 3, 2019
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1 change: 1 addition & 0 deletions NEWS.md
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Expand Up @@ -6,6 +6,7 @@ New language features

* Support for Unicode 12.1.0 ([#32002]).
* Methods can now be added to an abstract type ([#31916]).
* Added `sincosd(x)` to simultaneously compute the sine and cosine of `x`, where `x` is in degrees.
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Language changes
----------------
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1 change: 1 addition & 0 deletions base/exports.jl
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Expand Up @@ -324,6 +324,7 @@ export
sin,
sinc,
sincos,
sincosd,
sind,
sinh,
sinpi,
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2 changes: 1 addition & 1 deletion base/math.jl
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Expand Up @@ -6,7 +6,7 @@ export sin, cos, sincos, tan, sinh, cosh, tanh, asin, acos, atan,
asinh, acosh, atanh, sec, csc, cot, asec, acsc, acot,
sech, csch, coth, asech, acsch, acoth,
sinpi, cospi, sinc, cosc,
cosd, cotd, cscd, secd, sind, tand,
cosd, cotd, cscd, secd, sind, tand, sincosd,
acosd, acotd, acscd, asecd, asind, atand,
rad2deg, deg2rad,
log, log2, log10, log1p, exponent, exp, exp2, exp10, expm1,
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22 changes: 22 additions & 0 deletions base/special/trig.jl
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Expand Up @@ -1073,6 +1073,28 @@ end

tand(x::Real) = sind(x) / cosd(x)

"""
sincosd(x)

Simultaneously compute the sine and cosine of `x`, where `x` is in degrees.

!!! compat "Julia 1.3"
This function requires at least Julia 1.3.
"""
function sincosd(x::Real)
if isinf(x)
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Isn't these conditions checked in sind and cosd? Why check here?

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@ronisbr ronisbr Apr 13, 2019 •
edited
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Because without it, then the user will see an error on the function sind if Inf is passed. I though it could lead to confusion.

With respect of NaN, it can be removed. Do you want me to remove it? This was added when I was trying to make a function faster than calling both separated.

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I don't think we do error checking like that elsewhere though.

return throw(DomainError(x, "sincosd(x) is only defined for finite `x`."))
elseif isnan(x)
return (oftype(x,NaN), oftype(x,NaN))
end

# It turns out that calling those functions separately yielded better
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This is pretty surprising, any idea why? Part of the point of sincos, is it avoid the double cost of calling sin and cos on the same argument.

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@ronisbr ronisbr Mar 29, 2019 •
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I think the compiler is clever enough to remove those duplicated executions.

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In fact, the sincos_kernel use the same approach and it has a comment saying that inlining takes care of duplicated computations:

julia/base/special/trig.jl

Line 208 in 8221c87

# There's no need to write specialized kernels, as inlining takes care of remo-

# performance than considering each case and calling `sincos_kernel`.
return (sind(x), cosd(x))
end

sincosd(::Missing) = (missing, missing)

for (fd, f, fn) in ((:sind, :sin, "sine"), (:cosd, :cos, "cosine"), (:tand, :tan, "tangent"))
name = string(fd)
@eval begin
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15 changes: 15 additions & 0 deletions test/math.jl
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Expand Up @@ -369,9 +369,14 @@ end
@testset "degree-based trig functions" begin
@testset "$T" for T = (Float32,Float64,Rational{Int})
fT = typeof(float(one(T)))
fTsc = typeof( (float(one(T)), float(one(T))) )
for x = -400:40:400
@test sind(convert(T,x))::fT ≈ convert(fT,sin(pi/180*x)) atol=eps(deg2rad(convert(fT,x)))
@test cosd(convert(T,x))::fT ≈ convert(fT,cos(pi/180*x)) atol=eps(deg2rad(convert(fT,x)))

s,c = sincosd(convert(T,x))
@test s::fT ≈ convert(fT,sin(pi/180*x)) atol=eps(deg2rad(convert(fT,x)))
@test c::fT ≈ convert(fT,cos(pi/180*x)) atol=eps(deg2rad(convert(fT,x)))
end
@testset "sind" begin
@test sind(convert(T,0.0))::fT === zero(fT)
Expand All @@ -387,6 +392,16 @@ end
@test cosd(convert(T,-90))::fT === zero(fT)
@test cosd(convert(T,-270))::fT === zero(fT)
end
@testset "sincosd" begin
@test sincosd(convert(T,-360))::fTsc === ( -zero(fT), one(fT) )
@test sincosd(convert(T,-270))::fTsc === ( one(fT), zero(fT) )
@test sincosd(convert(T,-180))::fTsc === ( -zero(fT), -one(fT) )
@test sincosd(convert(T, -90))::fTsc === ( -one(fT), zero(fT) )
@test sincosd(convert(T, 0))::fTsc === ( zero(fT), one(fT) )
@test sincosd(convert(T, 90))::fTsc === ( one(fT), zero(fT) )
@test sincosd(convert(T, 180))::fTsc === ( zero(fT), -one(fT) )
@test sincosd(convert(T, 270))::fTsc === ( -one(fT), zero(fT) )
end

@testset "sinpi and cospi" begin
for x = -3:0.3:3
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