Week 2 Flashcards

1
Q

Rate and order of convergence of a sequence x_k of a numerical approximation of some exact quantity x*

A

x_k converges with order q to x* if

(For rate of convergence 0<μ<inf)

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2
Q

If q = 1? What does this mean for μ?

A

q=1 means linearly convergent

This means we must have 0<μ<=1 for convergence otherwise sequence diverges

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3
Q

1 sublinear convergence

A

1=μ

q=1

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4
Q

1 súper linear convergence

A

q>=1 and μ=0

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5
Q

Adjust Taylor series for f(x) for rate of convergence of newton method

A

Include quadratic term

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6
Q

Taylor series of Newton Method with quadratic

A

Two consecutive iterations

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7
Q

Rewrite Taylor series of newton method in terms of ε

A
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8
Q

Simplify ε Taylor expansion of newton method

A
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9
Q

Meaning of quadratic convergence in terms of error

A

Each successive ε reduces size of error by 2 orders of magnitude

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10
Q

ε Taylor’s expansion of newton method: double zero case

A
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11
Q

f(x) for Secant method formula

A
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12
Q

Secant q=?

A

(1+sqrt(5))/2

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13
Q

Find x_n using secant

A
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14
Q

Preferable value for q?

A

Higher

Eg: Newton > Secant

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15
Q

Taylor expansion of f(x) about x_0

A
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16
Q

When is newton method useful

A

Approximating f(x) = 0

for small |x - x_0|

17
Q

Another way to think of quadratic convergence

A

When the number of exact digits doubles on each iteration

18
Q

Limitations of Newton method

A

Requires derivative
If choosing starting point such that f’(x_0) is close to zero, x_1 will be huge and it may not converge (or will converge ridiculously well)

19
Q

Recursion relation for Newton method

A
20
Q

Draw diagram of Newton method labelling for 4 points

A
21
Q

Draw diagram of secant method with first 5 points

A
22
Q

Draw bisection method

A
23
Q

q= 1, μ =1

A

Sublinear convergence

24
Q

q>=1 and μ=0

A

1 super linear convergence