Objectives & Solving (m.solve)

The objective function defines the goal of mathematical optimization—whether to maximize profits, minimize costs, or minimize quadratic risk variance.

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Setting the Objective Function

Set the objective direction and formula declaratively using m.objective(maximize(...)) or m.objective(minimize(...)):

import { Model, expr, maximize, minimize } from "@ohtaman/washi";

const m = new Model("ProductionRevenue");
const x = m.integer("x", { lb: 0 });
const y = m.integer("y", { lb: 0 });

// Maximize revenue: 50*x + 40*y
m.objective(maximize(expr`50 * ${x} + 40 * ${y}`));

// Or minimize cost:
// m.objective(minimize(expr`10 * ${x} + 15 * ${y}`));

TIP

m.maximize(expr) and m.minimize(expr) remain available as backward-compatible convenience methods on Model.

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🚀 Solving the Model (m.solve())

Optimization is executed asynchronously by calling await m.solve():

const status = await m.solve({
  timeLimit: 10.0, // Timeout in seconds
  verbose: false,  // Enable/disable solver console logging
});

NOTE

m.optimize(options?) is preserved as a direct pass-through alias to m.solve(options?).

Solve Options

Option	Type	Default	Description
timeLimit	number	undefined	Maximum solve time limit in seconds.
verbose	boolean	false	When true, prints internal solver iteration logs.
mipGap	number	undefined	Relative optimality gap tolerance for MIP (e.g. 0.01 for 1%).
solver	"highs" | "z3" | "glpk" | string	"highs"	Target solver plugin to use for this execution.

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📊 Reading Results & Solver Status

After solving, query the status and optimal values:

const status = await m.solve();

// Solver Status ("Optimal", "Infeasible", "Unbounded", "TimeLimit")
console.log("Status:", status);

// Optimal Objective Value
console.log("Objective Value:", m.objectiveValue);

// Individual Variable Values
console.log("x =", x.value);
console.log("y =", y.value);

// Bulk Variable Values
const values = m.getValues({ x, y });
console.log(values); // { x: ..., y: ... }

Possible Status Values

Status	Meaning
"Optimal"	Global optimal solution found.
"Infeasible"	No solution exists that satisfies all constraints simultaneously.
"Unbounded"	The objective can increase/decrease indefinitely without violating constraints.
"TimeLimit"	The solver reached the specified time limit before proving optimality.
"Error"	Solver encountered an internal error.