Using FFTWLib (C#): Cannot find libfftw3-3.dll

Question

I'm trying to use Tamas Szalay's C# port of FFTW in Visual C# 2010, and I'm getting the above error when I try to use a function from FFTW (in this case fftw.malloc). That error goes away if I manually move the dll into the project's /bin/debug/ folder, but then I get

An attempt was made to load a program with an incorrect format.
(Exception from HRESULT: 0x8007000B)
Method: IntPtr malloc(Int32)

which makes me think I have a deeper problem.

Possibly relevant: I'm running this on an x64 machine, and DependencyWalker says that fftwlib.dll is built for x86.

score 2 · Answer 1 · answered Feb 27 '12 at 20:18

Just wanted to clarify things here since I am doing exactly the same thing: I am using an x64 machine but I set the platform of the solution in Visual Studio to x86 so I can use edit and continue.

There are both x86 and x64 versions of the FFTW DLL's. I keep them in separate directories for obvious reasons.
If you want to force use of the 32-bit DLL's, then set your platform to x86 and copy the 32-bit FFTW DLL's to the starting directory of the project (defaults to wherever it builds; for example, .\bin\Debug).

As an aside, I had to add CallingConvention = CallingConvention.Cdecl) to every DLLImport statement in FFTWlib otherwise VS2010 would complain.

Tamas Szalay C# port of FFTW link is broken. Were I can find the source code or another C# wrapper? — Pedro77, Jul 04 '13 at 13:23

Francisco Soto · Accepted Answer · 2012-02-07T23:33:00.493

1

You got to set your project CPU configuration to x86 instead of Any CPU if you are using external 32 bit code.

Any CPU is the default Visual Studio configuration, if you are running on a 64 bit OS, it will by default compile as 64 bit code, the problem is that if you need to load 32 bit DLLs like in your case, you will get format errors.

http://cl.ly/3s1J2q3u3E0n2F2y0z1K <-- screenshot where it is located.

edited Feb 07 '12 at 23:33

answered Feb 07 '12 at 04:18

Francisco Soto

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I'm afraid I'm using the Express version, which explains why I can't find a Target Configuration setting. – linkhyrule5 Feb 07 '12 at 23:29
Okay, so I downloaded the Professional trial and changed it to x86, but I'm still getting the same error. – linkhyrule5 Feb 08 '12 at 01:02
Turned out to be the opposite problem - switching it manually from x86 (default) to Any CPU fixed it. Well, that problem anyway, but the next one seems separate, so I'll make a new question for it. – linkhyrule5 Feb 08 '12 at 03:34
I think the DLL was 64 bits then and you were compiling to 32 bits! – Francisco Soto Feb 08 '12 at 03:41
@Soto: Except that DependencyWalker was saying x86... *confused* – linkhyrule5 Feb 13 '12 at 05:56

Using FFTWLib (C#): Cannot find libfftw3-3.dll

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