simplest animation causes high cpu usage and very high energy impact SpriteKit - animation

Question

Here is the simplest animation: a blackhole is rotating in the middle of the screen. These two lines of code increase cpu usage from 3% to 31% and energy impact from low to high (sometimes even very high):
let actionLoop = SKAction.repeatForever(SKAction.rotate(byAngle: CGFloat(360), duration: 1000))
hole.run(actionLoop)
Is this normal? I've read more or less similar discussions but haven't find a clear answer. Here is the whole code and screens:
import SpriteKit
import GameplayKit
class GameScene: SKScene {
// Basic for dynamic sizes step01
var width = CGFloat()
var height = CGFloat()
override func didMove(to view: SKView) {
// Basic for dynamic sizes step02
width = self.frame.size.width
height = self.frame.size.height
// test background color
self.backgroundColor = .yellow
// set blackhole
let hole = SKSpriteNode(imageNamed: "blackhole")
let startPosition = CGPoint(x: 0, y: 0)
hole.size = CGSize(width: width/8, height: width/8)
hole.position = CGPoint(x: startPosition.x, y: startPosition.y)
let actionLoop = SKAction.repeatForever(SKAction.rotate(byAngle: CGFloat(360), duration: 1000))
hole.run(actionLoop)
self.addChild(hole)
}
}
Update: And last but not least: it is not a simulator. I test it on the real device.

Answer 1

There are a couple of things your code does which might have impacted the efficiency.
First, SKAction rotation angles are calculated in radians (for the 360 degrees it should be 2*PI, which is roughly 6.28, not 360). As it stands, your code does lots of calculations to 'over-rotate' the sprite, which is wasteful. A better statement would be:
SKAction.rotate(byAngle: CGFloat.pi*2, duration: 1000)
Second, before rotating the sprite, you scale it by half using the corresponding function, which is also a bit wasteful, since each time the rotation is calculated, the scaling is also re-calculated to produce an accurate result. I'd suggest to pre-render a scaled-down version of the sprite and use that instead to save calculation times and load.