Open
Description
Today I was tracking down the test failure observed in JuliaMath/IntelVectorMath.jl#39 when moving to MKL_jll that occurred on a Mac.
After a while, with some help from @giordano, an MWE is:
# dlopen the libgomp inside CompilerSupportLibraries_jll (libgfortran 5).
using Libdl
dlopen("/Users/kristoffercarlsson/.julia/artifacts/411c17f069dd12b3f79b19e4647949050a58223c/lib/libgomp.1.dylib")
using MKL_jll
gamma1(x) = (x = copy(x); ccall((:vdTGamma, libmkl_rt), Cvoid, (Int32, Ptr{Float64}, Ptr{Float64}), length(x), x, x); x);
gamma2(x) = (y = similar(x); ccall((:vdTGamma, libmkl_rt), Cvoid, (Int32, Ptr{Float64}, Ptr{Float64}), length(x), x, y); y);
INPUT_2 = rand(1000);
gamma1(INPUT_2)[1:3]
gamma2(INPUT_2)[1:3]the result from gamma1 and gamma2 should give the same answers, but they don't, as an example
julia> gamma1(INPUT_2)[1:3]
3-element Array{Float64,1}:
Inf
Inf
Inf
julia> gamma2(INPUT_2)[1:3]
3-element Array{Float64,1}:
16.209046961478283
6.570129954697695
41.08264424860374(This doesn't seem to happen 100% of the time but the majority of the times).
This only happens if the length of the input vector is a certain size, cf
julia> gamma1(INPUT_2[1:602])[1:3] # ok
3-element Array{Float64,1}:
1.0650782774656853
1.4718294693439533
1.1884483595544906
julia> gamma2(INPUT_2[1:602])[1:3] # ok
3-element Array{Float64,1}:
1.0650782774656853
1.4718294693439533
1.1884483595544906
julia> gamma1(INPUT_2[1:603])[1:3] # bad
3-element Array{Float64,1}:
0.9663910468243027
0.8856476139287297
0.9213177809196278
julia> gamma2(INPUT_2[1:603])[1:3] # ok
3-element Array{Float64,1}:
1.0650782774656853
1.4718294693439533
1.1884483595544906The cutoff seems to be when the length of the vector is 603. My guess is that MKL thinks this is a long enough vector to perhaps enable threading? Also, it is important that libgomp is loaded before MKL_jll for the bug to occur.
The versions used are:
[e66e0078] CompilerSupportLibraries_jll v0.2.0+1
[856f044c] MKL_jll v2020.0.166+0
and
julia> versioninfo()
Julia Version 1.4.0-rc2.0
Commit b99ed72c95 (2020-02-24 16:51 UTC)
Platform Info:
OS: macOS (x86_64-apple-darwin19.0.0)
CPU: Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-8.0.1 (ORCJIT, skylake)Metadata
Metadata
Assignees
Labels
No labels