fftw_init_threads symbol not found on macOS (Apple Silicon) with system FFTW

[fcotizelati]

Hello,

I'm encountering a precompilation error with FFTW.jl on my macOS system running on Apple Silicon. The error indicates that the symbol fftw_init_threads is missing from the FFTW library.

When I try to run a script (which depends on FFTW.jl), I get the following error:

ERROR: InitError: could not load symbol "fftw_init_threads":
dlsym(0x..., fftw_init_threads): symbol not found
Stacktrace:
  [1] fftw_init_threads
    @ ~/.julia/packages/FFTW/mFpUb/src/providers.jl:69 [inlined]
  [2] __init__()
    @ FFTW ~/.julia/packages/FFTW/mFpUb/src/FFTW.jl:32
  ...

System Information

• macOS Version: macOS 15.4

• CPU/Architecture: Apple Silicon (M3)

• Julia Version: 1.11.4 (Official release)

Reproduction

A minimal reproduction involves a script that sets the following:

ENV["FFTW_LIBRARY_PATH"] = "/opt/homebrew/lib"
ENV["FFTW_LIBRARY"] = "/opt/homebrew/lib/libfftw3_threads.dylib"
ENV["FFTW_FORCE_SYSTEM_LIB"] = "true"
ENV["FFTW_INIT_THREADS"] = "0"
ENV["FFTW_NUM_THREADS"] = "1"
import Pkg
Pkg.build("FFTW")
using FFTW

And then I immediately get the error regarding fftw_init_threads.

I have also verified that the thread‑enabled library exports the symbol by running:

nm /opt/homebrew/lib/libfftw3_threads.dylib | grep fftw_init_threads

which returns a line such as:

00000000000048e8 T _fftw_init_threads

Is there a known workaround for this issue on macOS/Apple Silicon? How can I configure FFTW.jl to correctly use my system-provided FFTW, or should a patch be considered to disable threaded initialization on platforms where it is unavailable?

Thank you for your help and for maintaining FFTW.jl!

[kashish2210]

yup, this issue needs to be addressed cause when we are trying to use this library, it is throwing the same error "fftw_init_threads symbol not found" for macos ,

[stevengj]

For now, the workaround is to just use the bundled FFTW_jll library instead of homebrew. (Why do you need to use the homebrew version?)

[kashish2210]

hey @stevengj thank u for ur reply ,can I use some predefined configuration in the library for running the tests like this?

function configure_fftw_for_macos()
    @info "Configuring FFTW for macOS..."
    fftw_env_vars = ["FFTW_LIBRARY_PATH", "FFTW_LIBRARY", "FFTW_FORCE_SYSTEM_LIB"]
    for var in fftw_env_vars
        if haskey(ENV, var)
            @info "Removing existing FFTW environment variable: $var"
            delete!(ENV, var)
        end
    end
    @info "Setting up FFTW with FFTW_jll provider..."
    FFTW.set_provider!("fftw")
    Pkg.build("FFTW")
end

if Sys.isapple()
    @info "macOS detected, applying FFTW configurations..."
    configure_fftw_for_macos()
end

[stevengj]

Honestly, I didn't even know it was possible to make FFTW_jll use a system library instead of its own. (@giordano?)

I still don't know what you are trying to accomplish by trying to force it to use the homebrew FFTW lib. The regular FFTW_jll library works fine on Apple Silicon.

[giordano]

I didn't even know it was possible to make FFTW_jll use a system library instead of its own

It's possible via https://docs.binarybuilder.org/stable/jll/#Overriding-the-artifacts-in-JLL-packages, but that's not very discoverable from this package. I'm also quite puzzled by what people here are doing. The literal only result of googling FFTW_FORCE_SYSTEM_LIB is this page, so I have no clue of where that's coming from (at least if I exclude hallucinating LLMs)

[stevengj]

My best guess is that people are linking to some other library that links to a different version of libfftw3, sucking you into DLL hell?

If you just do using FFTW by itself in a fresh Julia, linking in no other package, does it work? (It works for me.)

[matteobachetti]

@stevengj it doesn't work for me:

I completely uninstalled fftw, removed the .julia directory, then

➜  sudo rm -r ~/.julia

➜  ~ julia
Checking for new Julia versions
Installing Julia 1.11.5+0.aarch64.apple.darwin14
Checking standard library notarization............................................................done.
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.11.5 (2025-04-14)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> import Pkg
julia> Pkg.add("FFTW")
u    Downloading [====================>           ]  62.4 
 F    Updating registry at `~/.julia/registries/General.to
   Resolving package versions...
   Installed AbstractFFTs ──── v1.5.0
  Progress [=========>                               ]  2/
   Installed MKL_jll ───────── v2025.0.1+1
  Progress [==============>                          ]  3/
   Installed IntelOpenMP_jll ─ v2025.0.4+0
  Progress [==================>                      ]  4/
   Installed oneTBB_jll ────── v2022.0.0+0
  Progress [=======================>                 ]  5/
   Installed JLLWrappers ───── v1.7.0
  Progress [===========================>             ]  6/
   Installed Reexport ──────── v1.2.2
  Progress [================================>        ]  7/
   Installed Preferences ───── v1.4.3
  Progress [====================================>    ]  8/
   Installed FFTW ──────────── v1.8.1
  Progress [========================================>]  9/
  Downloaded artifact: FFTW
  Downloaded artifact: oneTBB
    Updating `~/.julia/environments/v1.11/Project.toml`
  [7a1cc6ca] + FFTW v1.8.1
    Updating `~/.julia/environments/v1.11/Manifest.toml`
  [621f4979] + AbstractFFTs v1.5.0
  [7a1cc6ca] + FFTW v1.8.1
  [692b3bcd] + JLLWrappers v1.7.0
  [21216c6a] + Preferences v1.4.3
  [189a3867] + Reexport v1.2.2
  [f5851436] + FFTW_jll v3.3.11+0
  [1d5cc7b8] + IntelOpenMP_jll v2025.0.4+0
  [856f044c] + MKL_jll v2025.0.1+1
  [1317d2d5] + oneTBB_jll v2022.0.0+0
  [0dad84c5] + ArgTools v1.1.2
  [56f22d72] + Artifacts v1.11.0
  [2a0f44e3] + Base64 v1.11.0
  [ade2ca70] + Dates v1.11.0
  [f43a241f] + Downloads v1.6.0
  [7b1f6079] + FileWatching v1.11.0
  [4af54fe1] + LazyArtifacts v1.11.0
  [b27032c2] + LibCURL v0.6.4
  [76f85450] + LibGit2 v1.11.0
  [8f399da3] + Libdl v1.11.0
  [37e2e46d] + LinearAlgebra v1.11.0
  [56ddb016] + Logging v1.11.0
  [d6f4376e] + Markdown v1.11.0
  [ca575930] + NetworkOptions v1.2.0
  [44cfe95a] + Pkg v1.11.0
  [de0858da] + Printf v1.11.0
  [9a3f8284] + Random v1.11.0
  [ea8e919c] + SHA v0.7.0
  [fa267f1f] + TOML v1.0.3
  [a4e569a6] + Tar v1.10.0
  [cf7118a7] + UUIDs v1.11.0
  [4ec0a83e] + Unicode v1.11.0
  [e66e0078] + CompilerSupportLibraries_jll v1.1.1+0
  [deac9b47] + LibCURL_jll v8.6.0+0
  [e37daf67] + LibGit2_jll v1.7.2+0
  [29816b5a] + LibSSH2_jll v1.11.0+1
  [c8ffd9c3] + MbedTLS_jll v2.28.6+0
  [14a3606d] + MozillaCACerts_jll v2023.12.12
  [4536629a] + OpenBLAS_jll v0.3.27+1
  [83775a58] + Zlib_jll v1.2.13+1
  [8e850b90] + libblastrampoline_jll v5.11.0+0
  [8e850ede] + nghttp2_jll v1.59.0+0
  [3f19e933] + p7zip_jll v17.4.0+2
Precompiling project...
  9 dependencies successfully precompiled in 8 seconds. 25 already precompiled.

julia> using FFTW
ERROR: InitError: could not load symbol "fftw_init_threads":
dlsym(0x393007210, fftw_init_threads): symbol not found
Stacktrace:
  [1] fftw_init_threads
    @ ~/.julia/packages/FFTW/mFpUb/src/providers.jl:69 [inlined]
  [2] __init__()
    @ FFTW ~/.julia/packages/FFTW/mFpUb/src/FFTW.jl:32
  [3] run_module_init(mod::Module, i::Int64)
    @ Base ./loading.jl:1378
  [4] register_restored_modules(sv::Core.SimpleVector, pkg::Base.PkgId, path::String)
    @ Base ./loading.jl:1366
  [5] _include_from_serialized(pkg::Base.PkgId, path::String, ocachepath::String, depmods::Vector{…}, ignore_native::Nothing; register::Bool)
    @ Base ./loading.jl:1254
  [6] _include_from_serialized (repeats 2 times)
    @ ./loading.jl:1210 [inlined]
  [7] _require_search_from_serialized(pkg::Base.PkgId, sourcepath::String, build_id::UInt128, stalecheck::Bool; reasons::Dict{…}, DEPOT_PATH::Vector{…})
    @ Base ./loading.jl:2057
  [8] _require(pkg::Base.PkgId, env::String)
    @ Base ./loading.jl:2527
  [9] __require_prelocked(uuidkey::Base.PkgId, env::String)
    @ Base ./loading.jl:2388
 [10] #invoke_in_world#3
    @ ./essentials.jl:1089 [inlined]
 [11] invoke_in_world
    @ ./essentials.jl:1086 [inlined]
 [12] _require_prelocked(uuidkey::Base.PkgId, env::String)
    @ Base ./loading.jl:2375
 [13] macro expansion
    @ ./loading.jl:2314 [inlined]
 [14] macro expansion
    @ ./lock.jl:273 [inlined]
 [15] __require(into::Module, mod::Symbol)
    @ Base ./loading.jl:2271
 [16] #invoke_in_world#3
    @ ./essentials.jl:1089 [inlined]
 [17] invoke_in_world
    @ ./essentials.jl:1086 [inlined]
 [18] require(into::Module, mod::Symbol)
    @ Base ./loading.jl:2260
during initialization of module FFTW
Some type information was truncated. Use `show(err)` to see complete types.

[giordano]

@matteobachetti can you please show the output of

versioninfo()

?

[matteobachetti]

@giordano in the end, my problem was with DYLD_LIBRARY_PATH pointing to a directory where I had installed an old version of FFTW 😅. Unsetting that solved the problem.
Anyways...

Julia Version 1.11.5
Commit 760b2e5b739 (2025-04-14 06:53 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin24.0.0)
  CPU: 10 × Apple M1 Pro
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, apple-m1)
Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)
Environment:
  LD_LIBRARY_PATH = /Users/meo/lib

[giordano]

Was expecting as much, that's why I asked for the output of versioninfo, it'd show any DYLD_* environment variable. But I don't see that in your output, I presume you had already removed it? Also, for what is worth, setting LD_LIBRARY_PATH does nothing on macOS.

[matteobachetti]

Was expecting as much, that's why I asked for the output of versioninfo, it'd show any DYLD_* environment variable. But I don't see that in your output, I presume you had already removed it?

Yep

Also, for what is worth, setting LD_LIBRARY_PATH does nothing on macOS.

This is what happens when your .bashrc and .zsh contain 20+ years of information using Linux distributions spanning Gentoo to Ubuntu and Mac OS in two (maybe three now that I think of it) different architectures...