Difference between IJobForEachWithEntity nad and IJobForEach?

what is the difference between the two?

 

IJobForEachWithEntity includes parameters for entity and index in the Execute method. If you need entity access, or are using parallel or concurrent writers (i.e. EntityCommandBuffer.Concurrent) you should use that over IJobForEach.

 

so what do indexes show exactly?

 

They are just incrementing indexes for the entities and can be used as

jobIndex

for the

EntityCommandBuffer.Concurrent

interfaces.

jobIndex

"is used to playback the recorded commands in a deterministic order."

https://docs.unity3d.com/Packages/com.unity.entities@0.1/manual/entity_command_buffer.html

 

The index parameter can also be used to index a NativeArray that is the size of EntityQuery.CalculateEntityCount(). The ordering is stable for all usages between two structural change sync points.