NFFTNorsk Forening for Familieterapi
NFFTNonequispaced Fast Fourier Transform
NFFTnon-uniform fast Fourier transform
NFFTNonequidistant Fast Fourier Transform
NFFTNational Flag Football Tournament
NFFTNowVest Fidelity Funds Timer
NFFTNational Fantasy Football Tournament (Payday Sports, Inc.)
NFFTNational Fulltimers FunTeam (National Recreational Vehicle Owners Club)
NFFTNon-Face-to-Face Transaction
References in periodicals archive ?
Besides its simple structure and only O(N log N + M) arithmetic operations, this algorithm utilises m FFTs of size n compared to only one in the NFFT approach, uses a medium amount of extra memory, and is not suited for highly accurate computations; see Example 4.
Thus, for fixed [sigma] > 1, the approximation error introduced by the NFFT decays exponentially with the number m of summands in (2.
In the following, we suggest different methods for the compressed storage and application of the matrix B which are all available within our NFFT library by choosing particular flags in a simple way during the initialisation phase.
d] extra multiplications per node and is used within the NFFT by the flag PRE_LIN_PSI.
j] and these 2m + 1 values are computed only once within the NFFT and their amount is negligible.
Furthermore, it is faster than the default NFFT until an break even of N = 128.
a, p, m [member of] N, [sigma] [member of] Q (parameters for the NFFT summation algorithm)
The complexity estimates assume that the parameter [eta] for the NFFT summation algorithm is set to N.
In this step, the NFFT summation algorithm (Algorithm 3) is applied O([N.
k], the number of near-field evaluations performed in step 4 of the NFFT summation algorithm is bounded by O(aN log N), resulting in an overall complexity for the spherical filter of O([N.
1 tells us that step 4 of the NFFT summation algorithm (Algorithm 3) has a complexity of O(aN log N).
Since step 2 of the fast spherical filter (Algorithm 4) calls the NFFT summation O([N.