Class: CumulExpr

Remarks

Cumulative expression.

Cumulative expression represents resource usage over time. The resource could be a machine, a group of workers, a material, or anything of a limited capacity. The resource usage is not known in advance as it depends on the variables of the problem. Cumulative expressions allow us to model the resource usage and constrain it.

Basic cumulative expressions are:

• Pulse: the resource is used over an interval of time. For example, a pulse can represent a task requiring a certain number of workers during its execution. At the beginning of the interval, the resource usage increases by a given amount, and at the end of the interval, the resource usage decreases by the same amount. Pulse can be created by function Model.pulse or IntervalVar.pulse.
• Step: a given amount of resource is consumed or produced at a specified time (e.g., at the start of an interval variable). Steps may represent an inventory of a material that is consumed or produced by some tasks (a reservoir). Steps can be created by functions Model.stepAtStart, IntervalVar.stepAtStart, Model.stepAtEnd, IntervalVar.stepAtEnd. and Model.stepAt.

Cumulative expressions can be combined using CumulExpr.plus, CumulExpr.minus, CumulExpr.neg and Model.sum. The resulting cumulative expression represents a sum of the resource usage of the combined expressions.

Cumulative expressions can be constrained by CumulExpr.ge and CumulExpr.le to specify the minimum and maximum allowed resource usage.

Limitations:

• Pulse-based and step-based cumulative expressions cannot be mixed.
• Pulses cannot have negative height. Use - and unary - only with step-based expressions.

See CumulExpr.le and CumulExpr.ge for examples.

Extends

• ModelElement

Accessors

name

Get Signature

get name(): undefined | string

The name assigned to this model element.

Remarks

The name is optional and primarily useful for debugging purposes. When set, it helps identify the element in solver logs, error messages, and when inspecting solutions.

Names can be assigned to any model element including variables, expressions, and constraints.

Example

import * as CP from "optalcp";

const model = new CP.Model();

// Name a variable at creation
const task = model.intervalVar({ length: 10, name: "assembly" });

// Or set name later
const x = model.intVar({ min: 0, max: 100 });
x.name = "quantity";

console.log(task.name);  // "assembly"
console.log(x.name);     // "quantity"

Returns

undefined | string

Set Signature

set name(value: string): void

Parameters

Parameter	Type
value	string

Returns

void

Inherited from

ModelElement.name

Constructors

new CumulExpr()

new CumulExpr(): CumulExpr

Returns

CumulExpr

Inherited from

ModelElement.constructor

Methods

ge()

ge(minCapacity: number): Constraint

This function can be used to specify the minimum limit of resource usage at any time. minCapacity.

Parameters

Parameter	Type	Description
minCapacity	number	The minimum capacity value.

Returns

Constraint

The constraint object

Remarks

This function can be used to specify the minimum limit of resource usage at any time. For example to make sure that there is never less than zero material on stock. See Model.stepAtStart for an example with ge.

See

• Model.ge for the equivalent function on Model.
• Model.le for the opposite constraint.

---

le()

le(maxCapacity: number): Constraint

Constrains the cumulative function to be everywhere less or equal to maxCapacity.

Parameters

Parameter	Type	Description
maxCapacity	number	The maximum capacity value.

Returns

Constraint

The constraint object

Remarks

This function can be used to specify the maximum limit of resource usage at any time. For example, to limit the number of workers working simultaneously, limit the maximum amount of material on stock, etc. See Model.pulse for an example with le.

See

• Model.le for the equivalent function on Model.
• Model.ge for the opposite constraint.

---

minus()

minus(rhs: CumulExpr): CumulExpr

Subtraction of two cumulative expressions.

Parameters

Parameter	Type	Description
rhs	CumulExpr	The right-hand side cumulative expression.

Returns

CumulExpr

The resulting cumulative expression

Remarks

This function is the same as Model.minus.

---

neg()

neg(): CumulExpr

Negation of a cumulative expression.

Returns

CumulExpr

The resulting cumulative expression

Remarks

This function is the same as Model.neg.

---

plus()

plus(rhs: CumulExpr): CumulExpr

Addition of two cumulative expressions.

Parameters

Parameter	Type	Description
rhs	CumulExpr	The right-hand side cumulative expression.

Returns

CumulExpr

The resulting cumulative expression

Remarks

This function is the same as Model.plus.

Properties

Property	Modifier	Type
__brand	readonly	"CumulExpr"