Module accumulator 

Accumulators and decumulators — the daily-accrual structured products (“I-kill-you-later”): the holder is committed to trade a fixed quantity at a fixed price on every observation date while the structure is alive, with a knock-out barrier on the favorable side and geared (typically doubled) quantity on the adverse side.

• Accumulator: buy shares_per_day at strike K < S_0 each day; knocked out when the spot rises to the barrier H > S_0; when the spot closes below K the holder must buy gearing x the quantity. Day value while alive: q [ (S_i - K)+ - gearing (K - S_i)+ ].
• Decumulator: the mirror — sell at K > S_0, knocked out at H < S_0, geared when the spot closes above K.

Priced two ways:

• Analytical: each observation day is a pair of Reiner-Rubinstein knock-out barrier options maturing on that day (up-and-out call minus geared up-and-out put for the accumulator; down-and-out put minus geared down-and-out call for the decumulator), so the value is a strip of closed forms. The barrier is continuously monitored in this representation.
• Monte Carlo: simulates the observation grid directly, with the knock-out checked discretely at each observation — the usual contractual convention. The discrete knockout survives slightly longer than the continuous one, so the two conventions bracket the product; the tests assert exact agreement in the barrier-free degenerate cases and closeness with dense observations.

Structs

Accumulator

An accumulator/decumulator on equally spaced daily observations.

AccumulatorData

JSON contract data ("product_type": "accumulator").

AccumulatorPayoff

The accumulator as a mainline [Payoff], pricing inside EquityOption on the shared Monte Carlo engine (GBM, local vol and Heston via QE-M) — which gives it the market context for free: snapshot_market/npv_in rebinding, portfolio membership and the stress runner. The strike is the contract’s strike_price; spot, curve and surface come from the bound market. The standalone Accumulator remains the closed-form (continuously monitored) validation reference.

Enums

AccumulatorPricer

AccumulatorSide

Which side of the trade the holder accrues.