Performance surprise

[stevedevel]

I did a bit of performance testing to see and compare real numbers in my environment and was surprised. It seems like for AABB collision tests only there is a little javascript library that outperforms rapier by factor 3. Now I am trying to find out why this is the case.

As comparison I used @dimforge/rapier2d-compat and rbush. The numbers behind the name indicate number of colliders (or AABB boxes) and the number of collision tests. This is the result:

✓ src/test/collider.bench.ts > Collision detection 5948ms
     name                        hz     min      max     mean      p75      p99     p995     p999     rme  samples
   · rapier 100 100        1,023.06  0.5289  11.5042   0.9775   0.9625   3.4882   3.8919  11.5042  ±6.30%      514
   · rapier 1000 1000        162.83  4.6231  15.6322   6.1415   6.3853  15.6322  15.6322  15.6322  ±6.04%       82
   · rapierAABB 100 100      435.41  0.4990   8.3647   2.2967   2.8306   7.1766   7.2195   8.3647  ±7.52%      219
   · rapierAABB 1000 1000   73.9122  5.3738  22.8652  13.5296  15.6120  22.8652  22.8652  22.8652  ±9.80%       37
   · rbush-full 100 100    1,735.74  0.2431   1.9828   0.5761   0.7504   1.4453   1.5280   1.9828  ±3.23%      868
   · rbush-full 1000 1000    403.76  1.6046   6.1618   2.4767   3.0379   4.5408   5.5726   6.1618  ±4.66%      204
   · rbush 100 100         2,216.96  0.2167   2.2774   0.4511   0.5629   1.3377   1.6699   1.8349  ±2.91%     1109
   · rbush 1000 1000         397.27  1.3757   6.1402   2.5172   3.1722   5.5522   6.1402   6.1402  ±5.64%      199

 BENCH  Summary

  rbush 100 100 - src/test/collider.bench.ts > Collision detection
    1.28x faster than rbush-full 100 100
    2.17x faster than rapier 100 100
    5.09x faster than rapierAABB 100 100
    5.49x faster than rbush-full 1000 1000
    5.58x faster than rbush 1000 1000
    13.62x faster than rapier 1000 1000
    29.99x faster than rapierAABB 1000 1000

Did not expect that since rapier is implemented in WASM. On the other hand there might be lots of other factors in this case like whole purpose of the libraries used. rbush is specialized for AABB tests and rapier has always a hole bunch of overhead with different shapes, physics, etc. Or maybe I am using rapier in the wrong way. Anyways for those interested here is my code:

import { bench, describe } from 'vitest'
// @ts-ignore
import { RBush as RBushFull } from 'rbush-full/rbush'
import RBush from 'rbush';
import RAPIER from '@dimforge/rapier2d-compat';
await RAPIER.init()




function _rapierBench(colliderCount: number, collisionTestCount: number, half: number, areaLength: number) {


    // reset
    let world = new RAPIER.World({ x: 0, y: 9 })
    let collisionCount = 0

    for (var i = 0; i < colliderCount; i++) {
        const colliderDesc = RAPIER.ColliderDesc
            .cuboid(Math.random() * half, Math.random() * half)
            .setTranslation(Math.random() * areaLength - areaLength / 2, Math.random() * areaLength - areaLength / 2)
        world.createCollider(colliderDesc);
    }

    world.step()

    for (var i = 0; i < collisionTestCount; i++) {
        world.intersectionsWithPoint({ x: Math.random() * areaLength - areaLength / 2, y: Math.random() * areaLength - areaLength / 2 }, (collider: RAPIER.Collider) => {
            collisionCount++
            return true
        })
    }
    console.log(" Collisions: " + collisionCount)
}

function _rbushFullBench(colliderCount: number, collisionTestCount: number, half: number, areaLength: number) {

    let spatialIndex = new RBushFull()
    let collisionCount = 0
    let x, y, hw, hh

    for (var i = 0; i < colliderCount; i++) {
        x = Math.random() * areaLength - areaLength / 2
        y = Math.random() * areaLength - areaLength / 2
        hw = Math.random() * half
        hh = Math.random() * half
        spatialIndex.insert({
            bbox: [x - hw, y - hh, x + hw, y + hh],
            isStatic: false
        })
    }

    for (var i = 0; i < collisionTestCount; i++) {
        x = Math.random() * areaLength - areaLength / 2
        y = Math.random() * areaLength - areaLength / 2
        var result = spatialIndex.search([x - 1, y - 1, x + 1, y + 1])
        for (let i = 0; i < result.currentLen; i++) {

            collisionCount++
        }
    }
    console.log("Collisions: " + collisionCount)
}




function _rapierAABBBench(colliderCount: number, collisionTestCount: number, half: number, areaLength: number) {


    // reset
    let world = new RAPIER.World({ x: 0, y: 9 })
    let collisionCount = 0

    for (var i = 0; i < colliderCount; i++) {
        const colliderDesc = RAPIER.ColliderDesc
            .cuboid(Math.random() * half, Math.random() * half)
            .setTranslation(Math.random() * areaLength - areaLength / 2, Math.random() * areaLength - areaLength / 2)
        world.createCollider(colliderDesc);
    }

    //world.step()
    for (var i = 0; i < collisionTestCount; i++) {
        world.broadPhase.collidersWithAabbIntersectingAabb(world.narrowPhase, world.bodies, world.colliders,
            { x: Math.random() * areaLength - areaLength / 2, y: Math.random() * areaLength - areaLength / 2 },
            { x: 1, y: 1 },
            (handle) => {
                collisionCount++
                return true
            })
    }




    console.log(" Collisions: " + collisionCount)
}


function _rbushBench(colliderCount: number, collisionTestCount: number, half: number, areaLength: number) {

    let spatialIndex = new RBush()
    let collisionCount = 0
    let x, y, hw, hh
 
    for (var i = 0; i < colliderCount; i++) {
        x = Math.random() * areaLength - areaLength / 2
        y = Math.random() * areaLength - areaLength / 2
        hw = Math.random() * half
        hh = Math.random() * half
        spatialIndex.insert({
            minX: x - hw, 
            minY: y - hh,
            maxX: x + hw,
            maxY: y + hh,
            isStatic: false
        })
    }
  
    for (var i = 0; i < collisionTestCount; i++) {
        x = Math.random() * areaLength - areaLength / 2
        y = Math.random() * areaLength - areaLength / 2
        var result = spatialIndex.search({
            minX: x - 1, 
            minY: y - 1, 
            maxX: x + 1, 
            maxY: y + 1
        })
        for (let i = 0; i < result.length; i++) {
 
            collisionCount++
        }
    }
    console.log("Collisions: " + collisionCount)
}


describe('Collision detection', () => {

    bench('rapier 100 100', () => {
        _rapierBench(100, 100, 50, 10000)
    })
    bench('rapier 1000 1000', () => {
        _rapierBench(1000, 1000, 50, 10000)
    })

    bench('rapierAABB 100 100', () => {
        _rapierAABBBench(100, 100, 50, 10000)
    })
    bench('rapierAABB 1000 1000', () => {
        _rapierAABBBench(1000, 1000, 50, 10000)
    })

    bench('rbush-full 100 100', () => {
        _rbushFullBench(100, 100, 50, 10000)
    })
    bench('rbush-full 1000 1000', () => {
        _rbushFullBench(1000, 1000, 50, 10000)
    })

    bench('rbush 100 100', () => {
        _rbushBench(100, 100, 50, 10000)
    })
    bench('rbush 1000 1000', () => {
        _rbushBench(1000, 1000, 50, 10000)
    })
})