Numerical Analysis/Order of RK methods/Quiz on RK order

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1

What is the main importance of having a higher ODE method order

It always better to increase the accuracy of the solution
It requires fewer steps for the same accuracy restriction
We need the method to be better consistent
We need the method to be more stable
It provides better margin of stability

2

The number of slope predictions (number of k's) in an RK method is related to the order of the method as follows. The order of the method is:

exactly equal to the number slope predictions
equal to number of k's (slope evaluations) +1
upper bounded by the number of k's
not related to the number of k's

3

An n-th order of the method means that

the global truncation error is of the order
the local truncation error is of the order
the global truncation error is of the order
the maximum of the global and local error is n-th order

4

The order of the local truncation error is related to the global truncation error in the following way

they are about equal
they are not related
the global is one higher order than the local
the local is one higher order than the global

5

Is the following true? The global truncation error is always less then the local, since the errors partially cancel out over steps.

true
false

6

What is the highest order that we can achieve with a Runge Kutta type method by using 5 k's?

We can achieve 5-th order
That method is not used, since it is not consistent.
We can achieve 4-th order
We can achieve even higher order, it is sixth order accurate.

7

How is the order of single step methods related to consistency of the method?

At least first order of the method indicates that the method is consistent
To be consistent, a method must be second order or higher
not related at all, a single step method can be inconsistent and be of any order.

8

What is the main "tool" to prove the order of a numerical method for solving ODE's of type ?

Solving a specific "stiff" problem and showing that it converges for specific real positive K
Taylor series expansion for one variable
Taylor series expansion for one and two variables
Solving the ODE equation analytically and then numerically

9

If we show that all terms in a numerical method for ODE recurrence equation match the terms in the Taylor series expansion up to the terms with , but we do not analyze whether further cancellation of the terms exist, the following is true

The method is of the order n
The method is of the order n, since the global error is of the order
The order of the method could be higher than n-1, but it is at least n-1

10

If we use an explicit n-th (n>1) order accurate multistep method with s steps (s>2) to solve an ODE, but we use an n-1 order method to calculate the missing initial points that we need to start using the multistep method, what is the global order of accuracy of our calculation?

There is no such combined method, we cannot do that
The overall method is n-th order, since we just use the n-1 order method for few initial points
The overall method is of the order n-1, since the initial error from the lower accurate method remains in the cummulative error (global)
The order of the method could be either n or n-1
The order of the method is something between n-1 and n, just like the RK 45 method

11

What do we get as an order of error from the following expression

?

Something between and

12

What do we get as an order of error from the following expression

?

Something between and

13

What do we get as an order of error from the following expression

?

It must be of order