I wrote a program with Julia, but the performance is disappointing. The program is constructed with some functions, and global variables are prevented, arrays are well preallocated before used, the fft operation is accelerated by setting FFTW.set_num_threads(Sys.CPU_CORES). No red words are shown …

cis is faster than exp(im * ...), but not particularly optimized, it simply calls Complex(cos(x), sin(x)). This function should be a bit faster: const A = Ref{Cdouble}() const B = Ref{Cdouble}() function my_cis(x::Real) ccall((:sincos, Base.Math.libm), Void, (Cdouble, Ptr{Cdouble}, Ptr{Cdouble…

See also https://github.com/JuliaLang/julia/pull/21589 or the original fastmath only sincos implementation https://github.com/nacs-lab/yyc-data/blob/f717b873d8dece11703b90b8c1c03552368cf359/lib/NaCsCalc/src/utils.jl#L115-L141

Nice. Just to understand: what’s the problem with directly ccalling sincos? Ref is already used in modf, for example.

It’ll allocate memory. As mentioned in the PR, it’ll not be necessary once we can stack allocate those.

And the use of Ref in modf is not thread safe.

for i in 1:nt step_evolution_real!(u, p_fft!, prop_x, prop_p, ele[i], xplusy, prop_e) uo .= 0.0 for j2 in eachindex(p), j1 in eachindex(p) uo[j1+Δn, j2+Δn] = u[j1, j2] * splitter[j1, j2] * cis(A[i]*xplusy[j1, j2]) end for j in eachindex(u) u[j] *= 1 - splitter[j] end …

As other posts show, cis() is translated to a scalar function call. I suggest rewriting the expensive loops to use vector math library calls (via VML.jl, Yeppp.jl, etc.). The extra trouble with temporary arrays is often worthwhile in cases like this. Many Fortran compilers automatically use SIMD ve…

The VML.jl and Yeppp.jl are both sometimes helpful, but not in my condition. I need the exponential function for complex numbers. As I know these packages do not support complex numbers now.

But exp(z) = e^real(z) * (cos(imag(z)) + i * sin(imag(z)))

Poor performance of the cis() function

General Usage

DNF April 28, 2017, 2:54pm 9

Take a look at this thread, where there is a similar discussion, and with examples of using a vector library (AppleAccelerate in that case) to speed up cis.

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Poor performance of the cis() function

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