# FFTW.jl : could not load library "libfftw3"
**URL:** https://discourse.julialang.org/t/fftw-jl-could-not-load-library-libfftw3/60995
**Category:** General Usage
**Created:** [May 12, 2021, 3:43am UTC](https://discourse.julialang.org/t/fftw-jl-could-not-load-library-libfftw3/60995 "2021-05-12T03:43:00Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Ashwani\_Rathee](https://discourse.julialang.org/u/Ashwani_Rathee)
#### Post date: [May 12, 2021, 3:43am UTC](https://discourse.julialang.org/t/fftw-jl-could-not-load-library-libfftw3/60995/1 "2021-05-12T03:43:00Z")
I am facing this issue, I have provided the information that has been used to solve this issue. [https://github.com/JuliaMath/FFTW.jl/issues/110](https://github.com/JuliaMath/FFTW.jl/issues/110)
It’s local issue to my system and works fine for another contributor there.
```julia
(@v1.6) pkg> activate .
Activating environment at `~/julia-related/MusicProcessing.jl/Project.toml`
julia> using Revise
julia> using MusicProcessing
julia> using FFTW
julia> pathof(FFTW)
"/home/ashwani/.julia/packages/FFTW/Iu2GG/src/FFTW.jl"
julia> FFTW.libfftw3
"/home/ashwani/.julia/artifacts/81791030d1dcd08bf0c67b3e8224cb573d0f5a0a/lib/libfftw3.so"
julia> FFTW.libfftw3f
"/home/ashwani/.julia/artifacts/81791030d1dcd08bf0c67b3e8224cb573d0f5a0a/lib/libfftw3f.so"
julia> using Libdl
julia> Libdl.dlsym(Libdl.dlopen(FFTW.libfftw3), :fftw_threads_set_callback)
Ptr{Nothing} @0x00007fb0086c2c40
julia> using SHA
julia> bytes2hex(open(FFTW.libfftw3) do f; sha2_256(f); end)
"39042b7f2893eec46e184d358125be75eb196045b844421b2e9f7a90d80b25fa"
julia> bytes2hex(open(FFTW.libfftw3f) do f; sha2_256(f); end)
"da8463cf4325e73178e97fcd69b62f31707132aed390650ca8679881a6637de2"
# this is where issue is in my system
julia> Libdl.dlsym(Libdl.dlopen(FFTW.libfftw3f), :fftw_threads_set_callback)
ERROR: could not load symbol "fftw_threads_set_callback":
/home/ashwani/.julia/artifacts/81791030d1dcd08bf0c67b3e8224cb573d0f5a0a/lib/libfftw3f.so: undefined symbol: fftw_threads_set_callback
julia> audio_one_channel = SampleBuf(rand(1000), 10)
1000-element SampleBuf{Float64, 1}:
0.7188992365329432
0.9291267382769475
0.9235711252208105
0.7298652018343716
⋮
0.7817233868027189
0.9691375556064439
0.009171005643992869
julia> speedup(audio_one_channel, 1.5)
# also this doesn't make much sense yet to me
ERROR: could not load library "libfftw3"
libfftw3.so: cannot open shared object file: No such file or directory
Stacktrace:
[1] plan_dft_c2r_1d!
@ ~/julia-related/MusicProcessing.jl/src/complex.jl:22 [inlined]
[2] irfft!(dest::Vector{Float64}, src::Ptr{ComplexF64}, nfft::Int64)
@ MusicProcessing ~/julia-related/MusicProcessing.jl/src/complex.jl:35
[3] istft(stft::Matrix{ComplexF64}, samplerate::Float64, windowsize::Int64, hopsize::Int64; nfft::Int64, window::typeof(DSP.Windows.hanning))
@ MusicProcessing ~/julia-related/MusicProcessing.jl/src/TFR.jl:117
[4] istft
@ ~/julia-related/MusicProcessing.jl/src/TFR.jl:101 [inlined]
[5] #speedup#3
@ ~/julia-related/MusicProcessing.jl/src/audio.jl:99 [inlined]
[6] speedup (repeats 3 times)
@ ~/julia-related/MusicProcessing.jl/src/audio.jl:97 [inlined]
[7] top-level scope
@ REPL[15]:1
```
version info:
```julia
julia> versioninfo()
Julia Version 1.6.1
Commit 6aaedecc44 (2021-04-23 05:59 UTC)
Platform Info:
OS: Linux (x86_64-pc-linux-gnu)
CPU: Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-11.0.1 (ORCJIT, skylake)
```
---
### Author:  [@giordano](https://discourse.julialang.org/u/giordano)
#### Post date: [May 17, 2021, 11:41am UTC](https://discourse.julialang.org/t/fftw-jl-could-not-load-library-libfftw3/60995/2 "2021-05-17T11:41:25Z")
What if you replace
>
with
```julia
ccall((:fftw_plan_dft_c2r_1d, libfftw3), FFTW.PlanPtr, (Cint, Ptr{Complex{Float64}}, Ptr{Float64}, Cuint), nfft, src, dest, 0)
```
?
---
### Author:  [@Ashwani\_Rathee](https://discourse.julialang.org/u/Ashwani_Rathee)
#### Post date: [May 17, 2021, 12:00pm UTC](https://discourse.julialang.org/t/fftw-jl-could-not-load-library-libfftw3/60995/3 "2021-05-17T12:00:34Z")
When I use simply libfftw3 and this particular one is called in test, test throws this error
```julia
UndefVarError: libfftw3 not defined
```
and in these other functions as shown above by you in complex.jl, whenever they are called…below mentioned errors are thrown
```julia
Test threw exception
Expression: duration(speedup(audio_multi_channel, 2)) ≈ duration(audio_multi_channel) // 2
could not load library "libfftw3f"
libfftw3f.so: cannot open shared object file: No such file or directory
```
---
### Author:  [@giordano](https://discourse.julialang.org/u/giordano)
#### Post date: [May 17, 2021, 12:03pm UTC](https://discourse.julialang.org/t/fftw-jl-could-not-load-library-libfftw3/60995/4 "2021-05-17T12:03:12Z")
> [@Ashwani\_Rathee](#):
>
> When I use simply libfftw3 and this particular one is called in test, test throws this error
Did you actually import `FFTW` somewhere? I see it’s in the `Project.toml` of your package. If `FFTW` isn’t loaded how do you expect to be able to call into the library?
---
### Author:  [@Ashwani\_Rathee](https://discourse.julialang.org/u/Ashwani_Rathee)
#### Post date: [May 17, 2021, 12:07pm UTC](https://discourse.julialang.org/t/fftw-jl-could-not-load-library-libfftw3/60995/5 "2021-05-17T12:07:43Z")
It’s there in MusicProcessing.jl file, should I import libfftw3f and libfftw3 specifically?
---
### Author:  [@giordano](https://discourse.julialang.org/u/giordano)
#### Post date: [May 17, 2021, 12:18pm UTC](https://discourse.julialang.org/t/fftw-jl-could-not-load-library-libfftw3/60995/6 "2021-05-17T12:18:02Z")
You can also do `FFTW.libfftw3`, `FFTW.jl` doesn’t re-export that variable.
---
### Author:  [@Ashwani\_Rathee](https://discourse.julialang.org/u/Ashwani_Rathee)
#### Post date: [May 17, 2021, 12:28pm UTC](https://discourse.julialang.org/t/fftw-jl-could-not-load-library-libfftw3/60995/7 "2021-05-17T12:28:25Z")
Grazie, using this method and specifically importing those files worked for me:
```julia
import FFTW.libfftw3, FFTW.libfftw3f
.
.
function plan_dft_c2r_1d!(dest::ArrayLike{Float32}, src::ArrayLike{Complex{Float32}}, nfft::Int)
ccall((:fftwf_plan_dft_c2r_1d, libfftw3f), FFTW.PlanPtr, (Cint, Ptr{Complex{Float32}}, Ptr{Float32}, Cuint), nfft, src, dest, 0)
end
function plan_dft_c2r_1d!(dest::ArrayLike{Float64}, src::ArrayLike{Complex{Float64}}, nfft::Int)
ccall((:fftw_plan_dft_c2r_1d, libfftw3), FFTW.PlanPtr, (Cint, Ptr{Complex{Float64}}, Ptr{Float64}, Cuint), nfft, src, dest, 0)
end
```