Implements non-uniform fast Fourier transforms following [1, 2] with modifications to reduce memory usage. Instead of computing one large fast Fourier transform on the oversampled grid, the SNUFFTd words on shifted sub-grids. As a result, no arrays larger than the final output have to be allocated.

To compile the test executables, run

make

in the shell. They can then be run using:

test_nufftd_spread
test_sub_snufftd_spread

To compile the MEX interfaces, run

make

in the GNU Octave/MATLAB command line. The interfaces are then tested by running:

test_snufftd

[1] A. Dutt and V. Rokhlin, Fast Fourier transforms for nonequispaced data, SIAM Journal on Scientific Computing, 14 (1993), pp. 1368-1393.

[2] L. Greengard and J.-Y. Lee, Accelerating the nonuniform fast fourier transform, SIAM review, 46 (2004), pp. 443–454.