Andreas: You compare libopenlibm to the system libm
function test1()
const N=10000000;
@time begin
s = 0.0
for i=1:float(N)
s+= ccall((:sin,"libc"),Float64,(Float64,),i)
end
println(s)
end
@time begin
s = 0.0
for i=1:float(N)
s+=
Base.nan_dom_err(ccall((:sin,"libopenlibm"),Float64,(Float64,),i),i)
end
println(s)
end
@time begin
s::Float64 = 0.0
for i=1:float(N)
s += sin(i)
end
println(s)
end
end
test1 (generic function with 1 method)
does not give a significant difference between the built in `sin` function
and ccall.
Ivar
kl. 19:57:03 UTC+1 lørdag 1. mars 2014 skrev Andreas Noack Jensen følgende:
>
> But it is weird that if the definition from math.jl is added such that
>
> function test1()
> const N=10000000;
> @time begin
> s = 0.0
> for i=1:float(N)
> s+= ccall((:sin,"libc"),Float64,(Float64,),i)
> end
> println(s)
> end
> @time begin
> s = 0.0
> for i=1:float(N)
> s+= nan_dom_err(ccall((:sin,"libm"),Float64,(Float64,),i),i)
> end
> println(s)
> end
> @time begin
> s::Float64 = 0.0
> for i=1:float(N)
> s += sin(i)
> end
> println(s)
> end
> end
>
> I get
>
> julia> Newton.test1()
>
> 1.9558914085412562
> elapsed time: 0.437409166 seconds (136 bytes allocated)
> 1.9558914085412562
> elapsed time: 0.429992684 seconds (136 bytes allocated)
> 1.9558914085412367
> elapsed time: 2.495838008 seconds (136 bytes allocated)
>
>
>
> 2014-03-01 19:50 GMT+01:00 Ivar Nesje <[email protected] <javascript:>>:
> >
> > Why do you care for the performance of sin of big integers? I got about
> 2 time difference with your test function, but when I did the test with 1.2
> as the constant value to take sin of and got.
> >
> > julia> function test1()
> > const N=10000000;
> > @time begin
> > s = 0.0
> > for i=1:N
> > s+= ccall((:sin,"libc"),Float64,(Float64,),1.2)
> > end
> > println(s)
> > end
> > @time begin
> > s = 0.0
> > for i=1:N
> > s += sin(1.2)
> > end
> > println(s)
> > end
> > end
> > test1 (generic function with 1 method)
> >
> > julia> test1()
> > 9.320390858253522e6
> > elapsed time: 1.071002334 seconds (168 bytes allocated)
> > 9.320390858253522e6
> > elapsed time: 0.930658493 seconds (168 bytes allocated)
> >
> >
> > It would be expected that the native sin function in Julia would be
> slower than ccall to libc, because we check the return value to raise an
> exception (instead of a NaN value).
> >
> > We also use openlibm for our math functions, and the performance of that
> might be different from the libm on your system.
> >
> > Ivar
> >
> > kl. 18:53:39 UTC+1 lørdag 1. mars 2014 skrev Andrea Pagnani følgende:
> >>
> >> Dear all,
> >>
> >> julia's trigonometric functions seem to be almost 5 time slower than
> their libc counterpart (at least on my MacBook Pro OS X 10.9.2):
> >>
> >> function test1()
> >>
> >> const N=10000000;
> >> @time begin
> >> s = 0.0
> >> for i=1:N
> >> s+= ccall((:sin,"libc"),Float64,(Float64,),i)
> >> end
> >> println(s)
> >> end
> >> @time begin
> >> s = 0.0
> >> for i=1:N
> >> s += sin(i)
> >> end
> >> println(s)
> >> end
> >> end
> >>
> >>
> >> If you run this simple code you obtain
> >>
> >> julia> test1()
> >> 1.9558914085412562
> >> elapsed time: 0.275374895 seconds (88 bytes allocated)
> >> 1.9558914085412367
> >> elapsed time: 1.567108143 seconds (88 bytes allocated)
> >> 1.9558914085412367
> >>
> >> The same behaviour is obtained with other trigonometric functions
> >> Is this something to be expected?
>
>
>
>
> --
> Med venlig hilsen
>
> Andreas Noack Jensen
>
