Interop.cs

// The code in this file is provided courtesy of Tamas Szalay. Some functionality has been added.

// FFTWSharp
// ===========
// Basic C# wrapper for FFTW.
//
// Features
// ============
//    * Unmanaged function calls to main FFTW functions for both single and double precision
//    * Basic managed wrappers for FFTW plans and unmanaged arrays
//    * Test program that demonstrates basic functionality
//
// Notes
// ============
//    * Most of this was written in 2005
//    * Slightly updated since to get it running with Visual Studio Express 2010
//    * If you have a question about FFTW, ask the FFTW people, and not me. I did not write FFTW.
//    * If you have a question about this wrapper, probably still don't ask me, since I wrote it almost a decade ago.


using System;
using System.Runtime.InteropServices;

namespace FFTWSharp
{
	// Various Flags used by FFTW
	#region Enums
	/// <summary>
	/// FFTW planner flags
	/// </summary>
	[Flags]
	public enum fftw_flags : uint
	{
		/// <summary>
		/// Tells FFTW to find an optimized plan by actually computing several FFTs and measuring their execution time. 
		/// Depending on your machine, this can take some time (often a few seconds). Default (0x0). 
		/// </summary>
		Measure=0,
		/// <summary>
		/// Specifies that an out-of-place transform is allowed to overwrite its 
		/// input array with arbitrary data; this can sometimes allow more efficient algorithms to be employed.
		/// </summary>
		DestroyInput=1,
		/// <summary>
		/// Rarely used. Specifies that the algorithm may not impose any unusual alignment requirements on the input/output 
		/// arrays (i.e. no SIMD). This flag is normally not necessary, since the planner automatically detects 
		/// misaligned arrays. The only use for this flag is if you want to use the guru interface to execute a given 
		/// plan on a different array that may not be aligned like the original. 
		/// </summary>
		Unaligned=2,
		/// <summary>
		/// Not used.
		/// </summary>
		ConserveMemory=4,
		/// <summary>
		/// Like Patient, but considers an even wider range of algorithms, including many that we think are 
		/// unlikely to be fast, to produce the most optimal plan but with a substantially increased planning time. 
		/// </summary>
		Exhaustive=8,
		/// <summary>
		/// Specifies that an out-of-place transform must not change its input array. 
		/// </summary>
		/// <remarks>
		/// This is ordinarily the default, 
		/// except for c2r and hc2r (i.e. complex-to-real) transforms for which DestroyInput is the default. 
		/// In the latter cases, passing PreserveInput will attempt to use algorithms that do not destroy the 
		/// input, at the expense of worse performance; for multi-dimensional c2r transforms, however, no 
		/// input-preserving algorithms are implemented and the planner will return null if one is requested.
		/// </remarks>
		PreserveInput=16,
		/// <summary>
		/// Like Measure, but considers a wider range of algorithms and often produces a “more optimal” plan 
		/// (especially for large transforms), but at the expense of several times longer planning time 
		/// (especially for large transforms).
		/// </summary>
		Patient=32,
		/// <summary>
		/// Specifies that, instead of actual measurements of different algorithms, a simple heuristic is 
		/// used to pick a (probably sub-optimal) plan quickly. With this flag, the input/output arrays 
		/// are not overwritten during planning. 
		/// </summary>
		Estimate=64
	}

	/// <summary>
	/// Defines direction of operation
	/// </summary>
	public enum fftw_direction : int
	{
		/// <summary>
		/// Computes a regular DFT
		/// </summary>
		Forward=-1,
		/// <summary>
		/// Computes the inverse DFT
		/// </summary>
		Backward=1
	}

	/// <summary>
	/// Kinds of real-to-real transforms
	/// </summary>
	public enum fftw_kind : uint 
	{
		R2HC=0, 
		HC2R=1, 
		DHT=2,
		REDFT00=3, 
		REDFT01=4,
		REDFT10=5,
		REDFT11=6,
		RODFT00=7,
		RODFT01=8, 
		RODFT10=9, 
		RODFT11=10
	}
	#endregion

	// FFTW Interop Classes
	#region Single Precision
	/// <summary>
	/// Contains the Basic Interface FFTW functions for single-precision (float) operations
	/// </summary>
	public class fftwf
	{
		/// <summary>
		/// Allocates FFTW-optimized unmanaged memory
		/// </summary>
		/// <param name="length">Amount to allocate, in bytes</param>
		/// <returns>Pointer to allocated memory</returns>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_malloc",
			 ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr malloc(int length);

		/// <summary>
		/// Deallocates memory allocated by FFTW malloc
		/// </summary>
		/// <param name="mem">Pointer to memory to release</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_free",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void free(IntPtr mem);

		/// <summary>
		/// Deallocates an FFTW plan and all associated resources
		/// </summary>
		/// <param name="plan">Pointer to the plan to release</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_destroy_plan",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void destroy_plan(IntPtr plan);

		/// <summary>
		/// Clears all memory used by FFTW, resets it to initial state. Does not replace destroy_plan and free
		/// </summary>
		/// <remarks>After calling fftw_cleanup, all existing plans become undefined, and you should not 
		/// attempt to execute them nor to destroy them. You can however create and execute/destroy new plans, 
		/// in which case FFTW starts accumulating wisdom information again. 
		/// fftw_cleanup does not deallocate your plans; you should still call fftw_destroy_plan for this purpose.</remarks>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_cleanup",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void cleanup();

		/// <summary>
		/// Sets the maximum time that can be used by the planner.
		/// </summary>
		/// <param name="seconds">Maximum time, in seconds.</param>
		/// <remarks>This function instructs FFTW to spend at most seconds seconds (approximately) in the planner. 
		/// If seconds == -1.0 (the default value), then planning time is unbounded. 
		/// Otherwise, FFTW plans with a progressively wider range of algorithms until the the given time limit is 
		/// reached or the given range of algorithms is explored, returning the best available plan. For example, 
		/// specifying fftw_flags.Patient first plans in Estimate mode, then in Measure mode, then finally (time 
		/// permitting) in Patient. If fftw_flags.Exhaustive is specified instead, the planner will further progress to 
		/// Exhaustive mode. 
		/// </remarks>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_set_timelimit",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void set_timelimit(double seconds);

		/// <summary>
		/// Executes an FFTW plan, provided that the input and output arrays still exist
		/// </summary>
		/// <param name="plan">Pointer to the plan to execute</param>
		/// <remarks>execute (and equivalents) is the only function in FFTW guaranteed to be thread-safe.</remarks>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_execute",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void execute(IntPtr plan);
		
		/// <summary>
		/// Creates a plan for a 1-dimensional complex-to-complex DFT
		/// </summary>
		/// <param name="n">The logical size of the transform</param>
		/// <param name="direction">Specifies the direction of the transform</param>
		/// <param name="input">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_1d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_1d(int n, IntPtr input, IntPtr output, 
			fftw_direction direction, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 2-dimensional complex-to-complex DFT
		/// </summary>
		/// <param name="nx">The logical size of the transform along the first dimension</param>
		/// <param name="ny">The logical size of the transform along the second dimension</param>
		/// <param name="direction">Specifies the direction of the transform</param>
		/// <param name="input">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_2d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_2d(int nx, int ny, IntPtr input, IntPtr output, 
			fftw_direction direction, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 3-dimensional complex-to-complex DFT
		/// </summary>
		/// <param name="nx">The logical size of the transform along the first dimension</param>
		/// <param name="ny">The logical size of the transform along the second dimension</param>
		/// <param name="nz">The logical size of the transform along the third dimension</param>
		/// <param name="direction">Specifies the direction of the transform</param>
		/// <param name="input">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_3d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_3d(int nx, int ny, int nz, IntPtr input, IntPtr output, 
			fftw_direction direction, fftw_flags flags);

		/// <summary>
		/// Creates a plan for an n-dimensional complex-to-complex DFT
		/// </summary>
		/// <param name="rank">Number of dimensions</param>
		/// <param name="n">Array containing the logical size along each dimension</param>
		/// <param name="direction">Specifies the direction of the transform</param>
		/// <param name="input">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft(int rank, int[] n, IntPtr input, IntPtr output, 
			fftw_direction direction, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 1-dimensional real-to-complex DFT
		/// </summary>
		/// <param name="n">Number of REAL (input) elements in the transform</param>
		/// <param name="input">Pointer to an array of 4-byte real numbers</param>
		/// <param name="output">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_r2c_1d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_r2c_1d(int n, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 2-dimensional real-to-complex DFT
		/// </summary>
		/// <param name="nx">Number of REAL (input) elements in the transform along the first dimension</param>
		/// <param name="ny">Number of REAL (input) elements in the transform along the second dimension</param>
		/// <param name="input">Pointer to an array of 4-byte real numbers</param>
		/// <param name="output">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_r2c_2d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_r2c_2d(int nx, int ny, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 3-dimensional real-to-complex DFT
		/// </summary>
		/// <param name="nx">Number of REAL (input) elements in the transform along the first dimension</param>
		/// <param name="ny">Number of REAL (input) elements in the transform along the second dimension</param>
		/// <param name="nz">Number of REAL (input) elements in the transform along the third dimension</param>
		/// <param name="input">Pointer to an array of 4-byte real numbers</param>
		/// <param name="output">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_r2c_3d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_r2c_3d(int nx, int ny, int nz, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for an n-dimensional real-to-complex DFT
		/// </summary>
		/// <param name="rank">Number of dimensions</param>
		/// <param name="n">Array containing the number of REAL (input) elements along each dimension</param>
		/// <param name="input">Pointer to an array of 4-byte real numbers</param>
		/// <param name="output">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_r2c",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_r2c(int rank, int[] n, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 1-dimensional complex-to-real DFT
		/// </summary>
		/// <param name="n">Number of REAL (output) elements in the transform</param>
		/// <param name="input">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 4-byte real numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_c2r_1d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_c2r_1d(int n, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 2-dimensional complex-to-real DFT
		/// </summary>
		/// <param name="nx">Number of REAL (output) elements in the transform along the first dimension</param>
		/// <param name="ny">Number of REAL (output) elements in the transform along the second dimension</param>
		/// <param name="input">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 4-byte real numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_c2r_2d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_c2r_2d(int nx, int ny, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 3-dimensional complex-to-real DFT
		/// </summary>
		/// <param name="nx">Number of REAL (output) elements in the transform along the first dimension</param>
		/// <param name="ny">Number of REAL (output) elements in the transform along the second dimension</param>
		/// <param name="nz">Number of REAL (output) elements in the transform along the third dimension</param>
		/// <param name="input">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 4-byte real numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_c2r_3d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_c2r_3d(int nx, int ny, int nz, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for an n-dimensional complex-to-real DFT
		/// </summary>
		/// <param name="rank">Number of dimensions</param>
		/// <param name="n">Array containing the number of REAL (output) elements along each dimension</param>
		/// <param name="input">Pointer to an array of 8-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 4-byte real numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_dft_c2r",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_c2r(int rank, int[] n, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 1-dimensional real-to-real DFT
		/// </summary>
		/// <param name="n">Number of elements in the transform</param>
		/// <param name="input">Pointer to an array of 4-byte real numbers</param>
		/// <param name="output">Pointer to an array of 4-byte real numbers</param>
		/// <param name="kind">The kind of real-to-real transform to compute</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_r2r_1d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr r2r_1d(int n, IntPtr input, IntPtr output, fftw_kind kind, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 2-dimensional real-to-real DFT
		/// </summary>
		/// <param name="nx">Number of elements in the transform along the first dimension</param>
		/// <param name="ny">Number of elements in the transform along the second dimension</param>
		/// <param name="input">Pointer to an array of 4-byte real numbers</param>
		/// <param name="output">Pointer to an array of 4-byte real numbers</param>
		/// <param name="kindx">The kind of real-to-real transform to compute along the first dimension</param>
		/// <param name="kindy">The kind of real-to-real transform to compute along the second dimension</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_r2r_2d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr r2r_2d(int nx, int ny, IntPtr input, IntPtr output, 
			fftw_kind kindx, fftw_kind kindy, fftw_flags flags);
		
		/// <summary>
		/// Creates a plan for a 3-dimensional real-to-real DFT
		/// </summary>
		/// <param name="nx">Number of elements in the transform along the first dimension</param>
		/// <param name="ny">Number of elements in the transform along the second dimension</param>
		/// <param name="nz">Number of elements in the transform along the third dimension</param>
		/// <param name="input">Pointer to an array of 4-byte real numbers</param>
		/// <param name="output">Pointer to an array of 4-byte real numbers</param>
		/// <param name="kindx">The kind of real-to-real transform to compute along the first dimension</param>
		/// <param name="kindy">The kind of real-to-real transform to compute along the second dimension</param>
		/// <param name="kindz">The kind of real-to-real transform to compute along the third dimension</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_r2r_3d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr r2r_3d(int nx, int ny, int nz, IntPtr input, IntPtr output, 
			fftw_kind kindx, fftw_kind kindy, fftw_kind kindz, fftw_flags flags);

		/// <summary>
		/// Creates a plan for an n-dimensional real-to-real DFT
		/// </summary>
		/// <param name="rank">Number of dimensions</param>
		/// <param name="n">Array containing the number of elements in the transform along each dimension</param>
		/// <param name="input">Pointer to an array of 4-byte real numbers</param>
		/// <param name="output">Pointer to an array of 4-byte real numbers</param>
		/// <param name="kind">An array containing the kind of real-to-real transform to compute along each dimension</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_plan_r2r",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr r2r(int rank, int[] n, IntPtr input, IntPtr output, 
			fftw_kind[] kind, fftw_flags flags);

		/// <summary>
		/// Returns (approximately) the number of flops used by a certain plan
		/// </summary>
		/// <param name="plan">The plan to measure</param>
		/// <param name="add">Reference to double to hold number of adds</param>
		/// <param name="mul">Reference to double to hold number of muls</param>
		/// <param name="fma">Reference to double to hold number of fmas (fused multiply-add)</param>
		/// <remarks>Total flops ~= add+mul+2*fma or add+mul+fma if fma is supported</remarks>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_flops",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void flops(IntPtr plan, ref double add, ref double mul, ref double fma);

		/// <summary>
		/// Outputs a "nerd-readable" version of the specified plan to stdout
		/// </summary>
		/// <param name="plan">The plan to output</param>
		[DllImport("libfftw3f-3.dll",
			 EntryPoint = "fftwf_print_plan",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void print_plan(IntPtr plan);

        /// <summary>
        /// Exports the accumulated Wisdom to the provided filename
        /// </summary>
        /// <param name="filename">The target filename</param>
        [DllImport("libfftw3f-3.dll",
             EntryPoint = "fftwf_export_wisdom_to_filename",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
        public static extern void export_wisdom_to_filename(string filename);


        /// <summary>
        /// Imports Wisdom from provided filename
        /// </summary>
        /// <param name="filename">The filename to read from</param>
        [DllImport("libfftw3f-3.dll",
             EntryPoint = "fftwf_import_wisdom_from_filename",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
        public static extern void import_wisdom_from_filename(string filename);

        /// <summary>
        /// Forgets the Wisdom
        /// </summary>
        [DllImport("libfftw3f-3.dll",
             EntryPoint = "fftwf_forget_wisdom",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
        public static extern void fftwf_forget_wisdom();
    }
    #endregion

    #region Double Precision
    /// <summary>
    /// Contains the Basic Interface FFTW functions for double-precision (double) operations
    /// </summary>
    public class fftw
	{
		/// <summary>
		/// Allocates FFTW-optimized unmanaged memory
		/// </summary>
		/// <param name="length">Amount to allocate, in bytes</param>
		/// <returns>Pointer to allocated memory</returns>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_malloc",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr malloc(int length);

		/// <summary>
		/// Deallocates memory allocated by FFTW malloc
		/// </summary>
		/// <param name="mem">Pointer to memory to release</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_free",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void free(IntPtr mem);

		/// <summary>
		/// Deallocates an FFTW plan and all associated resources
		/// </summary>
		/// <param name="plan">Pointer to the plan to release</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_destroy_plan",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void destroy_plan(IntPtr plan);

		/// <summary>
		/// Clears all memory used by FFTW, resets it to initial state. Does not replace destroy_plan and free
		/// </summary>
		/// <remarks>After calling fftw_cleanup, all existing plans become undefined, and you should not 
		/// attempt to execute them nor to destroy them. You can however create and execute/destroy new plans, 
		/// in which case FFTW starts accumulating wisdom information again. 
		/// fftw_cleanup does not deallocate your plans; you should still call fftw_destroy_plan for this purpose.</remarks>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_cleanup",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void cleanup();

		/// <summary>
		/// Sets the maximum time that can be used by the planner.
		/// </summary>
		/// <param name="seconds">Maximum time, in seconds.</param>
		/// <remarks>This function instructs FFTW to spend at most seconds seconds (approximately) in the planner. 
		/// If seconds == -1.0 (the default value), then planning time is unbounded. 
		/// Otherwise, FFTW plans with a progressively wider range of algorithms until the the given time limit is 
		/// reached or the given range of algorithms is explored, returning the best available plan. For example, 
		/// specifying fftw_flags.Patient first plans in Estimate mode, then in Measure mode, then finally (time 
		/// permitting) in Patient. If fftw_flags.Exhaustive is specified instead, the planner will further progress to 
		/// Exhaustive mode. 
		/// </remarks>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_set_timelimit",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void set_timelimit(double seconds);

		/// <summary>
		/// Executes an FFTW plan, provided that the input and output arrays still exist
		/// </summary>
		/// <param name="plan">Pointer to the plan to execute</param>
		/// <remarks>execute (and equivalents) is the only function in FFTW guaranteed to be thread-safe.</remarks>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_execute",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void execute(IntPtr plan);
		
		/// <summary>
		/// Creates a plan for a 1-dimensional complex-to-complex DFT
		/// </summary>
		/// <param name="n">The logical size of the transform</param>
		/// <param name="direction">Specifies the direction of the transform</param>
		/// <param name="input">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_1d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_1d(int n, IntPtr input, IntPtr output, 
			fftw_direction direction, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 2-dimensional complex-to-complex DFT
		/// </summary>
		/// <param name="nx">The logical size of the transform along the first dimension</param>
		/// <param name="ny">The logical size of the transform along the second dimension</param>
		/// <param name="direction">Specifies the direction of the transform</param>
		/// <param name="input">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_2d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_2d(int nx, int ny, IntPtr input, IntPtr output, 
			fftw_direction direction, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 3-dimensional complex-to-complex DFT
		/// </summary>
		/// <param name="nx">The logical size of the transform along the first dimension</param>
		/// <param name="ny">The logical size of the transform along the second dimension</param>
		/// <param name="nz">The logical size of the transform along the third dimension</param>
		/// <param name="direction">Specifies the direction of the transform</param>
		/// <param name="input">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_3d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_3d(int nx, int ny, int nz, IntPtr input, IntPtr output, 
			fftw_direction direction, fftw_flags flags);

		/// <summary>
		/// Creates a plan for an n-dimensional complex-to-complex DFT
		/// </summary>
		/// <param name="rank">Number of dimensions</param>
		/// <param name="n">Array containing the logical size along each dimension</param>
		/// <param name="direction">Specifies the direction of the transform</param>
		/// <param name="input">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft(int rank, int[] n, IntPtr input, IntPtr output, 
			fftw_direction direction, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 1-dimensional real-to-complex DFT
		/// </summary>
		/// <param name="n">Number of REAL (input) elements in the transform</param>
		/// <param name="input">Pointer to an array of 8-byte real numbers</param>
		/// <param name="output">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_r2c_1d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_r2c_1d(int n, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 2-dimensional real-to-complex DFT
		/// </summary>
		/// <param name="nx">Number of REAL (input) elements in the transform along the first dimension</param>
		/// <param name="ny">Number of REAL (input) elements in the transform along the second dimension</param>
		/// <param name="input">Pointer to an array of 8-byte real numbers</param>
		/// <param name="output">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_r2c_2d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_r2c_2d(int nx, int ny, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 3-dimensional real-to-complex DFT
		/// </summary>
		/// <param name="nx">Number of REAL (input) elements in the transform along the first dimension</param>
		/// <param name="ny">Number of REAL (input) elements in the transform along the second dimension</param>
		/// <param name="nz">Number of REAL (input) elements in the transform along the third dimension</param>
		/// <param name="input">Pointer to an array of 8-byte real numbers</param>
		/// <param name="output">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_r2c_3d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_r2c_3d(int nx, int ny, int nz, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for an n-dimensional real-to-complex DFT
		/// </summary>
		/// <param name="rank">Number of dimensions</param>
		/// <param name="n">Array containing the number of REAL (input) elements along each dimension</param>
		/// <param name="input">Pointer to an array of 8-byte real numbers</param>
		/// <param name="output">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_r2c",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_r2c(int rank, int[] n, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 1-dimensional complex-to-real DFT
		/// </summary>
		/// <param name="n">Number of REAL (output) elements in the transform</param>
		/// <param name="input">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 8-byte real numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_c2r_1d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_c2r_1d(int n, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 2-dimensional complex-to-real DFT
		/// </summary>
		/// <param name="nx">Number of REAL (output) elements in the transform along the first dimension</param>
		/// <param name="ny">Number of REAL (output) elements in the transform along the second dimension</param>
		/// <param name="input">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 8-byte real numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_c2r_2d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_c2r_2d(int nx, int ny, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 3-dimensional complex-to-real DFT
		/// </summary>
		/// <param name="nx">Number of REAL (output) elements in the transform along the first dimension</param>
		/// <param name="ny">Number of REAL (output) elements in the transform along the second dimension</param>
		/// <param name="nz">Number of REAL (output) elements in the transform along the third dimension</param>
		/// <param name="input">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 8-byte real numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_c2r_3d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_c2r_3d(int nx, int ny, int nz, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for an n-dimensional complex-to-real DFT
		/// </summary>
		/// <param name="rank">Number of dimensions</param>
		/// <param name="n">Array containing the number of REAL (output) elements along each dimension</param>
		/// <param name="input">Pointer to an array of 16-byte complex numbers</param>
		/// <param name="output">Pointer to an array of 8-byte real numbers</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_dft_c2r",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr dft_c2r(int rank, int[] n, IntPtr input, IntPtr output, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 1-dimensional real-to-real DFT
		/// </summary>
		/// <param name="n">Number of elements in the transform</param>
		/// <param name="input">Pointer to an array of 8-byte real numbers</param>
		/// <param name="output">Pointer to an array of 8-byte real numbers</param>
		/// <param name="kind">The kind of real-to-real transform to compute</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_r2r_1d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr r2r_1d(int n, IntPtr input, IntPtr output, fftw_kind kind, fftw_flags flags);

		/// <summary>
		/// Creates a plan for a 2-dimensional real-to-real DFT
		/// </summary>
		/// <param name="nx">Number of elements in the transform along the first dimension</param>
		/// <param name="ny">Number of elements in the transform along the second dimension</param>
		/// <param name="input">Pointer to an array of 8-byte real numbers</param>
		/// <param name="output">Pointer to an array of 8-byte real numbers</param>
		/// <param name="kindx">The kind of real-to-real transform to compute along the first dimension</param>
		/// <param name="kindy">The kind of real-to-real transform to compute along the second dimension</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_r2r_2d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr r2r_2d(int nx, int ny, IntPtr input, IntPtr output, 
			fftw_kind kindx, fftw_kind kindy, fftw_flags flags);
		
		/// <summary>
		/// Creates a plan for a 3-dimensional real-to-real DFT
		/// </summary>
		/// <param name="nx">Number of elements in the transform along the first dimension</param>
		/// <param name="ny">Number of elements in the transform along the second dimension</param>
		/// <param name="nz">Number of elements in the transform along the third dimension</param>
		/// <param name="input">Pointer to an array of 8-byte real numbers</param>
		/// <param name="output">Pointer to an array of 8-byte real numbers</param>
		/// <param name="kindx">The kind of real-to-real transform to compute along the first dimension</param>
		/// <param name="kindy">The kind of real-to-real transform to compute along the second dimension</param>
		/// <param name="kindz">The kind of real-to-real transform to compute along the third dimension</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_r2r_3d",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr r2r_3d(int nx, int ny, int nz, IntPtr input, IntPtr output, 
			fftw_kind kindx, fftw_kind kindy, fftw_kind kindz, fftw_flags flags);

		/// <summary>
		/// Creates a plan for an n-dimensional real-to-real DFT
		/// </summary>
		/// <param name="rank">Number of dimensions</param>
		/// <param name="n">Array containing the number of elements in the transform along each dimension</param>
		/// <param name="input">Pointer to an array of 8-byte real numbers</param>
		/// <param name="output">Pointer to an array of 8-byte real numbers</param>
		/// <param name="kind">An array containing the kind of real-to-real transform to compute along each dimension</param>
		/// <param name="flags">Flags that specify the behavior of the planner</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_plan_r2r",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern IntPtr r2r(int rank, int[] n, IntPtr input, IntPtr output, 
			fftw_kind[] kind, fftw_flags flags);

		/// <summary>
		/// Returns (approximately) the number of flops used by a certain plan
		/// </summary>
		/// <param name="plan">The plan to measure</param>
		/// <param name="add">Reference to double to hold number of adds</param>
		/// <param name="mul">Reference to double to hold number of muls</param>
		/// <param name="fma">Reference to double to hold number of fmas (fused multiply-add)</param>
		/// <remarks>Total flops ~= add+mul+2*fma or add+mul+fma if fma is supported</remarks>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_flops",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void flops(IntPtr plan, ref double add, ref double mul, ref double fma);

		/// <summary>
		/// Outputs a "nerd-readable" version of the specified plan to stdout
		/// </summary>
		/// <param name="plan">The plan to output</param>
		[DllImport("libfftw3-3.dll",
			 EntryPoint = "fftw_print_plan",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
		public static extern void print_plan(IntPtr plan);

        /// <summary>
        /// Exports the accumulated Wisdom to the provided filename
        /// </summary>
        /// <param name="filename">The target filename</param>
        [DllImport("libfftw3-3.dll",
             EntryPoint = "fftw_export_wisdom_to_filename",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
        public static extern void export_wisdom_to_filename(string filename);


        /// <summary>
        /// Imports Wisdom from provided filename
        /// </summary>
        /// <param name="filename">The filename to read from</param>
        [DllImport("libfftw3-3.dll",
             EntryPoint = "fftw_import_wisdom_from_filename",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
        public static extern void import_wisdom_from_filename(string filename);

        /// <summary>
        /// Forgets the Wisdom
        /// </summary>
        [DllImport("libfftw3-3.dll",
             EntryPoint = "fftw_forget_wisdom",
             ExactSpelling = true,
             CallingConvention = CallingConvention.Cdecl)]
        public static extern void fftw_forget_wisdom();
    }
    #endregion
}