taskgraph_ts/tasks/implementation/cost-benefit/ev-calculation.md at main

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glm-5.1 6016e81162 feat(cost-benefit): implement calculateTaskEv pure function

Implement the core EV calculation: EV = p*C_success + (1-p)*C_fail
where C_success = scopeCost*impactWeight, C_fail = scopeCost*impactWeight + fallbackCost + timeLost*expectedRetries.

- expectedRetries = (1-p)/p when p>0, else 0 (geometric series)
- Caps expectedRetries at config.retries when retries > 0
- Multiplies final EV by config.valueRate when non-zero
- 30 unit tests covering formula, edge cases, and Python research model values

2026-04-27 11:51:59 +00:00

2.2 KiB

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id, name, status, depends_on, scope, risk, impact, level

name

status

depends_on

scope

risk

impact

level

cost-benefit/ev-calculation

Implement calculateTaskEv pure function

completed

schema/numeric-methods-and-defaults

schema/result-types

narrow

low

component

implementation

Description

Implement calculateTaskEv(p, scopeCost, impactWeight, config?): EvResult in src/analysis/cost-benefit.ts. This is the pure math function — takes numeric inputs, returns EV result. No graph dependency.

Per cost-benefit.md:

EV = P_success × C_success + (1 - P_success) × C_fail

Where C_fail = scopeCost + fallbackCost + timeLost × expectedRetries.

Acceptance Criteria

calculateTaskEv(p: number, scopeCost: number, impactWeight: number, config?: EvConfig): EvResult
Returns EvResult: { ev, pSuccess, expectedRetries }
expectedRetries = (1 - p) / p when p > 0, else 0 (geometric series)
C_fail = scopeCost * impactWeight + fallbackCost + timeLost * expectedRetries (impactWeight scales the cost)
EV = p * scopeCost * impactWeight + (1-p) * C_fail
When config.retries is provided and > 0, caps expectedRetries at retries
When config.valueRate is non-zero, multiplies the final EV
Edge cases: p = 0 (guaranteed failure), p = 1 (guaranteed success), default config (all zeros)
Unit tests: known calculations from the Python research model, boundary values, config variations

References

docs/architecture/cost-benefit.md — EV formula, EvConfig parameters, EvResult
docs/architecture/api-surface.md — calculateTaskEv signature
docs/architecture/schemas.md — EvConfig, EvResult schemas

Notes

All acceptance criteria verified via 30 unit tests covering formula correctness, edge cases, config variations, and known Python research model values.

Summary

Implemented calculateTaskEv pure function in src/analysis/cost-benefit.ts.

Modified: src/analysis/cost-benefit.ts — full implementation of calculateTaskEv
Modified: test/cost-benefit.test.ts — 30 comprehensive unit tests
Tests: 30, all passing (286 total across suite)
Lint: clean (tsc --noEmit passes)

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