Yes, I have compared the first and second call of ground(), the second call is obviously faster. But the second one is still too slow, compared to the Matlab version.
在 2015年12月15日星期二 UTC+8上午1:49:16，Jean-François Baffier写道： > > Before checking the code, I have a short question. As Julia is interpreted > language, the first execution of a function will include compilation of > your code. Do you compare the time for Julia on a second call of your > function or on the first call? > > You can read the related performance tips here > <http://docs.julialang.org/en/stable/manual/performance-tips/>. > > Le lundi 14 décembre 2015 12:35:43 UTC+9, 博陈 a écrit : >> >> This is my first julia code, I am happy it did the right thing, but >> compared with the Matlab code that did the same thing, it runs so slowly. >> The Matlab code takes about 90s, but the julia below takes 130s. >> >> Potential(x::Float64, y::Float64) = -2./sqrt(x^2+1.) -2./sqrt(y^2+1.) + >> 1./sqrt((x-y)^2+1.) >> Ko(x::Float64,y::Float64) = x^2+y^2 >> >> function ground() >> R = 320. >> Ks = 2^11 >> x = linspace(-R, R, Ks+1) >> dx = 2R/Ks >> dt = 0.1 >> pm = 2π/2dx >> px = circshift( linspace(-pm, pm, Ks+1), round(Int64, Ks/2) ) >> FFTW.set_num_threads(8) >> >> V = Float64[Potential(ix, iy) for ix in x, iy in x] >> ko = Float64[e^(-dt/4* (Ko(ipx,ipy))) for ipx in px, ipy in px] >> ko2 = ko.^2 >> vo = Float64[e^(-dt* (Potential(ix,iy))) for ix in x, iy in x] >> ϕ = Array(Complex128,(Ks+1,Ks+1)) >> Pl = plan_fft!(ϕ; flags=FFTW.MEASURE) >> ϕ = V.*complex(1.) >> >> normphi = sqrt(sumabs2(ϕ))*dx >> ϕ /= normphi >> >> ϕ = Pl*ϕ >> ϕ .*= ko >> ϕ = Pl\ϕ >> >> Δϕ = 1. >> nstep = 0 >> print("start loop") >> while Δϕ > 1.e-15 >> ϕ′ = ϕ >> ϕ .*= vo >> >> normphi = sqrt(sumabs2(ϕ))*dx >> ϕ /= normphi >> >> ϕ = Pl*ϕ >> ϕ .*= ko2 >> ϕ = Pl\ϕ >> # if check Δϕ for every step, 35s is needed. >> if nstep>500 >> Δϕ = maxabs(ϕ-ϕ′) >> end >> nstep += 1 >> if mod(nstep,200)==0 >> print(nstep," ") >> print("Δϕ=",Δϕ," ") >> end >> >> end >> ϕ .*= vo >> >> ϕ = Pl*ϕ >> ϕ .*= ko >> ϕ = Pl\ϕ >> >> normphi = sqrt(sumabs2(ϕ))*dx >> ϕ /= normphi >> end >> >>
