Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 | 6x 6x 8x 6x 6x 6x 6x 6x 138x 12x 126x 6x 7x 7x 7x 7x 7x 7x 28x 28x 28x 28x 28x 5x 23x 1x 1x | import { RootFinderOptions, IRootFinder, Root } from '../definition'
import { Polynomial } from '../../polynomial'
import { isValidRoot } from '../../utils'
export class NewtonRootFinder implements IRootFinder {
constructor(protected readonly options: RootFinderOptions) {}
protected autoEstimate(polynomial: Polynomial): number {
const coefficients = polynomial.getCoefficients()
const { length } = coefficients
let positive: number = 0
let negative: number = 0
coefficients.forEach(coefficient => {
if (coefficient > 0) {
positive += coefficient
} else {
negative -= coefficient
}
})
return (positive / negative - 1) / length + 1
}
public findRoot(polynomial: Polynomial): Root {
const epsilon = this.options.epsilon!
const { estimate } = this.options
const maxIterations = this.options.maxIterations!
let iteration: number = 0
let root: number =
estimate === 'auto' ? this.autoEstimate(polynomial) : estimate!
while (iteration++ < maxIterations) {
const tangent = polynomial.getTangentAt(root)
const newRoot = tangent.findRoot().value
const delta = Math.abs(newRoot - root)
root = newRoot
if (delta < epsilon) {
return {
converged: true,
iterations: iteration,
value: root,
}
}
if (!isValidRoot(root)) {
return {
converged: false,
iterations: iteration,
value: root,
}
}
}
return {
converged: false,
iterations: iteration - 1,
value: root,
}
}
}
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