Struct Poseidon1Constants 

pub struct Poseidon1Constants<F, const WIDTH: usize> {
    pub rounds_f: usize,
    pub rounds_p: usize,
    pub mds_circ_col: [i64; WIDTH],
    pub round_constants: Vec<[F; WIDTH]>,
}

Raw Poseidon1 parameters before the sparse matrix optimization.

These are the “textbook” parameters as generated by the Grain LFSR or any other parameter-generation script. They are transformed into the optimized sparse form used at runtime.

Round Constant Layout

Constants are stored in a flat array with three consecutive sections:

  ┌──────────────┬──────────────────┬──────────────────┐
  │ initial full  │  partial rounds  │  terminal full   │
  │ (RF/2 items)  │  (RP items)      │  (RF/2 items)    │
  └──────────────┴──────────────────┴──────────────────┘

Each entry is a WIDTH-sized vector (one constant per state element per round).

Fields

rounds_f: usize

Total number of full rounds (split equally between initial and terminal).

rounds_p: usize

Number of partial rounds.

mds_circ_col: [i64; WIDTH]

First column of the circulant MDS matrix, stored as signed integers.

This matches the representation used by the MDS crate, so concrete fields can pass their verified constants directly without duplication. During initialization, the dense form is expanded once for the sparse decomposition, then discarded.

round_constants: Vec<[F; WIDTH]>

Round constants, one WIDTH-sized vector per round.

Total length = rounds_f + rounds_p.

Implementations

impl<F: PrimeField, const WIDTH: usize> Poseidon1Constants<F, WIDTH>

pub fn to_optimized( &self, ) -> (FullRoundConstants<F, WIDTH>, PartialRoundConstants<F, WIDTH>)

Compute the optimized sparse-form constants from these raw parameters.

This performs two transformations:

1. Sparse matrix decomposition: factors the dense MDS matrix into one dense transition matrix and several sparse matrices. Each sparse matrix is parameterized by two vectors of length WIDTH-1.

2. Round constant compression: via backward substitution through the inverse MDS matrix, reduces each partial round’s full constant vector to a single scalar, except for the first partial round.

Trait Implementations

impl<F: Clone, const WIDTH: usize> Clone for Poseidon1Constants<F, WIDTH>

fn clone(&self) -> Poseidon1Constants<F, WIDTH>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<F: Debug, const WIDTH: usize> Debug for Poseidon1Constants<F, WIDTH>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.