Class {

#name : #PMMidpointStepper,

#superclass : #PMExplicitStepper,

#category : #'Math-ODE'

}

{ #category : #accessing }

PMMidpointStepper class >> order [

"Midpoint is a second order method."

^ 2

]

{ #category : #stepping }

PMMidpointStepper >> doStep: aState time: t [

"This method should take one step from inState at time t of size dt, and modify the state, then answer it."

| k1 k2 |

self stepSize isNil

ifTrue: [ self error: 'step size required by stepper' ].

k1 := system state: aState time: t.

k2 := system state: (aState + (self stepSize*(1/ 2)* k1)) time: t + (self stepSize *(1/ 2)).

^ aState + (k2 * self stepSize).

]

{ #category : #stepping }

PMMidpointStepper >> lastStep: aState time: t stepSize: timeStep deltaT: incrementOfTime [

"This method should take one step from inState at time t of size dt, and modify the state, then answer it."

self stepSize: timeStep.

^ self doStep: aState time: t .

]