/// <summary>
/// Performs a complex-to-real inverse fast fourier transformation.
/// </summary>
/// <seealso cref="http://www.fftw.org/fftw3_doc/One_002dDimensional-DFTs-of-Real-Data.html#One_002dDimensional-DFTs-of-Real-Data"/>
/// <seealso cref="http://www.fftw.org/fftw3_doc/Multi_002dDimensional-DFTs-of-Real-Data.html#Multi_002dDimensional-DFTs-of-Real-Data"/>
public static void IFFT(IPinnedArray <Complex> input, IPinnedArray <double> output, PlannerFlags plannerFlags = PlannerFlags.Default, int nThreads = 1)
{
if ((plannerFlags & PlannerFlags.Estimate) == PlannerFlags.Estimate)
{
using (var plan = FftwPlanRC.Create(output, input, DftDirection.Backwards, plannerFlags, nThreads))
{
plan.Execute();
return;
}
}
using (var plan = FftwPlanRC.Create(output, input, DftDirection.Backwards, plannerFlags | PlannerFlags.WisdomOnly, nThreads))
{
if (plan != null)
{
plan.Execute();
return;
}
}
/// If with <see cref="PlannerFlags.WisdomOnly"/> no plan can be created
/// and <see cref="PlannerFlags.Estimate"/> is not specified, we use
/// a different buffer to avoid overwriting the input
using (var bufferContainer = _bufferPool.RequestBuffer(input.Length * Marshal.SizeOf <Complex>() + MemoryAlignment))
using (var buffer = new AlignedArrayComplex(bufferContainer.Buffer, MemoryAlignment, input.GetSize()))
using (var plan = FftwPlanRC.Create(output, buffer, DftDirection.Backwards, plannerFlags, nThreads))
{
input.CopyTo(plan.BufferComplex);
plan.Execute();
}
}
static void Transform(IPinnedArray <Complex> input, IPinnedArray <Complex> output, DftDirection direction, PlannerFlags plannerFlags, int nThreads)
{
if ((plannerFlags & PlannerFlags.Estimate) == PlannerFlags.Estimate)
{
using (var plan = FftwPlanC2C.Create(input, output, direction, plannerFlags, nThreads))
{
plan.Execute();
return;
}
}
using (var plan = FftwPlanC2C.Create(input, output, direction, plannerFlags | PlannerFlags.WisdomOnly, nThreads))
{
if (plan != null)
{
plan.Execute();
return;
}
}
/// If with <see cref="PlannerFlags.WisdomOnly"/> no plan can be created
/// and <see cref="PlannerFlags.Estimate"/> is not specified, we use
/// a different buffer to avoid overwriting the input
if (input != output)
{
using (var plan = FftwPlanC2C.Create(output, output, input.Rank, input.GetSize(), direction, plannerFlags, nThreads))
{
input.CopyTo(output);
plan.Execute();
}
}
else
{
using (var bufferContainer = _bufferPool.RequestBuffer(input.Length * Marshal.SizeOf <Complex>() + MemoryAlignment))
using (var buffer = new AlignedArrayComplex(bufferContainer.Buffer, MemoryAlignment, input.GetSize()))
using (var plan = FftwPlanC2C.Create(buffer, buffer, input.Rank, input.GetSize(), direction, plannerFlags, nThreads))
{
input.CopyTo(plan.Input);
plan.Execute();
plan.Output.CopyTo(output, 0, 0, input.Length);
}
}
}
