Default sin / cos functions do not scale on multithreading

[yuyichao]

@DavidBerghaus

I am using the default sin / cos functions and this post:

github.com/JuliaLang/julia

Issue: No performance scaling in threading

opened by ranjanan on 2016-07-13

Consider the following code: using Base.Threads println(“Number of threads = $(nthreads())”) x = rand(10^6) y = zeros(10^6) println(“Warmup!”) for i = 1:10^6 y[i] = sin(x[i])^2 + cos(x[i])^2 end t1…

multithreading performance

led me to the idea that the sin / cos could cause the issue.

Again, that post has nothing to do with BigFloat.

@DavidBerghaus

It confirmed that this function is not threadsafe:
1 Threads: 347.428779 seconds (552.06 M allocations: 48.274 GiB, 0.93% gc time)
4 Threads: 118.963835 seconds (525.86 M allocations: 43.746 GiB, 4.19% gc time)
28 Threads: 137.302679 seconds (211.11 M allocations: 10.939 GiB, 8.41% gc time)
40 Threads: 125.110352 seconds (201.09 M allocations: 10.696 GiB, 10.58% gc time)
56 Threads: 119.466149 seconds (195.01 M allocations: 10.744 GiB, 11.99% gc time)

This only suggest that the mpfr ones do not scale well, also has nothing to so with thread safety.