Struct FftPoisson 

pub struct FftPoisson {
    pub shape: [usize; 3],
    pub dx: [f64; 3],
    /* private fields */
}

Periodic-boundary-condition Poisson solver using 3D FFTs, O(N^3 log N).

Solves nabla^2 Phi = 4piG*rho spectrally: forward-transform rho, multiply by the Green’s function -1/k^2, and inverse-transform to obtain Phi. The z-axis exploits Hermitian symmetry via R2C/C2R transforms; x and y use full C2C.

Best suited for cosmological periodic boxes where the domain wraps on all axes. FFT plans are precomputed at construction and reused across all solve() calls.

Fields

shape: [usize; 3]

Number of grid cells along each spatial axis [nx, ny, nz].

dx: [f64; 3]

Grid spacing along each spatial axis [dx, dy, dz].

Implementations

impl FftPoisson

pub fn new(domain: &Domain) -> Self

Create a new periodic Poisson solver, precomputing all FFT plans for the given domain.

Trait Implementations

impl PoissonSolver for FftPoisson

fn solve(&self, density: &DensityField, g: f64) -> PotentialField

Solve nabla^2 Phi = 4piG*rho with periodic BC via spectral Green’s function.

Forward-transforms rho (R2C), divides by -k^2 in Fourier space (zeroing the DC mode to remove the mean), and inverse-transforms (C2R) to obtain the potential.

fn compute_acceleration(&self, potential: &PotentialField) -> AccelerationField

Compute the gravitational acceleration g = -grad(Phi) via spectral differentiation.

Forward-transforms Phi, multiplies each component by -i*k_j, and inverse-transforms to obtain gx, gy, gz. All three components are computed in a single parallel pass.

fn set_progress(&mut self, p: Arc<StepProgress>)

Attach shared progress state for intra-phase cell-level reporting.