How to reproduce:
1. Open tester-submitted project (Raytracer.zip)
2. Open scene "raytracer.unity"
4. Play the scene
5. Comment out "[ComputeJobOptimization]" at RaytraceSystem.cs line 24
6. Play the scene again

Expected result: [ComputeJobOptimization] gives performance increase
Actual result: [ComputeJobOptimization] decreases performance

Reproducible with: 2018.1.0b12 (Unity Job System preview build)
Not reproducible with:
5.6, 2017.1, 2017.2, 2017.3, 2017.4 - Unity Job System was not implemented
2018.1, 2018.2 - missing libraries and project compatibility problems

Notes:

• With [ComputeJobOptimization(Accuracy.Low, Support.Relaxed)], frame times were roughly around 155ms
• Without [ComputeJobOptimization], frame times were roughly around 28.5ms

Reproduced on:

• PC
• Windows 10 64bit
• Intel(R) Xeon(R) W-2145 CPU @ 3.70GHz
• 32GB RAM
• Radeon(TM) Pro WX 9100