Struct ApproxTopN 

pub struct ApproxTopN(pub usize);

Retain n terms, cutting at an octave of |c|² instead of selecting exactly.

Every octave of |c|² that fits whole is kept from the top down; the first that does not fit, the boundary octave, contributes as many terms as fit in n, the first in bucket order (rank order across partitions). A sum of more than n terms keeps exactly n (fewer only if coefficients are NaN), and n == 0 clears. Which boundary-octave terms survive is not a semantic promise. Partition-exact: a split sum’s octave histogram is the sum of its partitions’, so every partition cuts at the boundary one partition would.

Tuple Fields

0: usize

The retained term count.

Trait Implementations

impl Clone for ApproxTopN

fn clone(&self) -> ApproxTopN

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ApproxTopN

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

Formats the value using the given formatter.

impl From<ApproxTopN> for BuiltinTruncation

fn from(p: ApproxTopN) -> Self

Converts to this type from the input type.

impl PartialEq for ApproxTopN

fn eq(&self, other: &ApproxTopN) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<const W: usize> TruncationPolicy<W> for ApproxTopN

fn finalize_layer_partitioned( &self, local: &mut PauliSum<W>, collectives: &dyn Collectives, )

One allreduce_sum_u64 of [len, histogram…], the single-partition edge walk, and at a boundary one more of the per-rank boundary counts for this rank’s quota; no early exit, since that would desynchronize the group.

fn finalize_layer(&self, sum: &mut PauliSum<W>)

Pass over the whole sum after each layer; PauliSum::retain is the easy way to write a filter here.

fn supports_partitioned(&self) -> bool

Whether finalize_layer_partitioned runs above one partition; every partitioned driver checks it before the first layer.

fn keep_term(&self, _x: &[u64; W], _z: &[u64; W], _c: Complex64) -> bool

Per-term filter, run inside the merge on every output, so it must be cheap.

fn finalizes_layer(&self) -> bool

Whether finalize_layer does anything, a hint that lets the engine skip it.

impl Copy for ApproxTopN

impl StructuralPartialEq for ApproxTopN