Struct ExpDecayPayout

pub struct ExpDecayPayout;

The ExpDecayPayout model computes rewards using a continuous exponential decay based on the input variable.

Concept: Smooth Decay Function

Formula

reward = r0 * e^(-a * x)

Signed Arithmetic

The exponent -a * x is always non-positive for a >= 0 and x >= 0. Unsigned fixed-point types cannot represent negative numbers, so the negation is performed inside a concrete FixedI128 workspace via FixedSignedCast, then projected back. This makes the model correct for both signed and unsigned Asset and FixedPoint types.

Characteristics:

• Continuous decay: Smooth reduction instead of stepwise halving.
• Non-linear scaling: Faster decay as a increases.
• Deterministic: Same input and parameters yield identical results.
• Fixed-point safe: Signed intermediate arithmetic via FixedSignedCast.
• Works with unsigned types: No Neg bound; negation in FixedI128.
• Context-driven: Controlled via ExpDecayPayoutConfig.

Applications:

• Emission schedules with smooth decay.
• Staking reward tapering.
• Time-based incentive reduction.
• Economic stabilization mechanisms.

Use Cases

• Replacing halving with a smoother continuous decay.
• Gradual reward reduction without abrupt drops.
• Fine-tuned monetary policy control.

Example

let config = ExpDecayPayoutConfig {
    initial_reward: 1000u128,
    decay_constant: FixedU128::saturating_from_rational(1, 10), // a = 0.1
};
// x = 10: reward = 1000 * e^(-1.0) ~= 367
assert_eq!(ExpDecayPayout::compute(10u128, Some(config)), 367);

Trait Implementations

impl Debug for ExpDecayPayout

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

Formats the value using the given formatter.

impl Default for ExpDecayPayout

fn default() -> ExpDecayPayout

Returns the “default value” for a type.

impl<FixedPoint, Asset> PurePluginModel<Asset, ExpDecayPayoutConfig<Asset, FixedPoint>, Asset> for ExpDecayPayout

where Asset: Copy + IntegerToFixed + FixedForInteger<FixedPoint = FixedPoint>, FixedPoint: FixedPointNumber + FixedSignedCast<Signed = FixedI128>,

fn compute( &self, x: Asset, context: &ExpDecayPayoutConfig<Asset, FixedPoint>, ) -> Asset

Computes the model’s output for a given immutable input and context.