Enum BuiltinTruncation 

pub enum BuiltinTruncation {
    Keep,
    Coefficient(f64),
    Weight(u32),
    TopN(usize),
    ApproxTopN(usize),
    CollapseSample(Arc<CollapseSample>),
    And(Box<BuiltinTruncation>, Box<BuiltinTruncation>),
    Or(Box<BuiltinTruncation>, Box<BuiltinTruncation>),
}

Any builtin policy or combinator as one runtime value, the form the device drivers take.

Each variant truncates exactly as the builtin it names, and every builtin converts into one with From; a custom TruncationPolicy does not. A tree holding an exact TopN cannot run above one partition (supports_partitioned is false). Or combines per-term filters only: build it with or or try_or, which reject an operand with a layer pass; a hand-built Or variant that holds one panics in finalizes_layer and supports_partitioned. Clone shares a CollapseSample rather than copying it, so every clone continues the same trajectory.

Variants

Keep

No truncation.

Coefficient(f64)

CoefficientThreshold(eps).

Weight(u32)

WeightCutoff(k).

TopN(usize)

TopN(n).

ApproxTopN(usize)

ApproxTopN(n).

CollapseSample(Arc<CollapseSample>)

CollapseSample.

And(Box<BuiltinTruncation>, Box<BuiltinTruncation>)

And of two policies.

Or(Box<BuiltinTruncation>, Box<BuiltinTruncation>)

Or of two per-term filters.

Implementations

impl BuiltinTruncation

pub fn or(first: BuiltinTruncation, second: BuiltinTruncation) -> Self

first or second, both per-term filters.

Panics

If either operand has a layer pass (see try_or).

pub fn try_or( first: BuiltinTruncation, second: BuiltinTruncation, ) -> Result<Self, String>

first or second, or the reason it is rejected: an operand with a layer pass (TopN, ApproxTopN, CollapseSample, or an And containing one).

pub fn supports_partitioned(&self) -> bool

Whether the tree runs above one partition: false exactly when it holds an exact TopN.

Panics

On an Or variant holding a layer pass.

pub fn contains_collapse_sample(&self) -> bool

Whether a CollapseSample appears anywhere in the tree, Or branches included.

Trait Implementations

impl Clone for BuiltinTruncation

fn clone(&self) -> BuiltinTruncation

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for BuiltinTruncation

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

Formats the value using the given formatter.

impl<P: Clone + Into<BuiltinTruncation>> From<&P> for BuiltinTruncation

A borrowed policy converts as its clone does.

fn from(p: &P) -> Self

Converts to this type from the input type.

impl<A: Into<BuiltinTruncation>, B: Into<BuiltinTruncation>> From<And<A, B>> for BuiltinTruncation

fn from(p: And<A, B>) -> Self

Converts to this type from the input type.

impl From<ApproxTopN> for BuiltinTruncation

fn from(p: ApproxTopN) -> Self

Converts to this type from the input type.

impl From<Arc<CollapseSample>> for BuiltinTruncation

fn from(p: Arc<CollapseSample>) -> Self

Converts to this type from the input type.

impl From<CoefficientThreshold> for BuiltinTruncation

fn from(p: CoefficientThreshold) -> Self

Converts to this type from the input type.

impl From<CollapseSample> for BuiltinTruncation

fn from(p: CollapseSample) -> Self

Converts to this type from the input type.

impl<A: Into<BuiltinTruncation>, B: Into<BuiltinTruncation>> From<Or<A, B>> for BuiltinTruncation

Panics

If either operand has a layer pass, as BuiltinTruncation::or.

fn from(p: Or<A, B>) -> Self

Converts to this type from the input type.

impl From<TopN> for BuiltinTruncation

fn from(p: TopN) -> Self

Converts to this type from the input type.

impl From<WeightCutoff> for BuiltinTruncation

fn from(p: WeightCutoff) -> Self

Converts to this type from the input type.

impl PartialEq for BuiltinTruncation

fn eq(&self, other: &BuiltinTruncation) -> 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 BuiltinTruncation

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

Arm for arm finalize_layer, each leaf by its own collective form.

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 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 finalizes_layer(&self) -> bool

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

fn supports_partitioned(&self) -> bool

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

impl StructuralPartialEq for BuiltinTruncation