How to Fix Overlapping Write Ranges in an IJobParallelFor in Unity

Your parallel job sometimes produces wrong values or trips the job safety system, because Execute(i) writes to output[i+1] or a shared accumulator. Parallel batches must not overlap writes. Here is how to fix the access pattern.

How to fix it

1. Write only your own index

Inside Execute(int i), write exclusively to output[i]. Never write to neighboring indices, since another batch owns them and may run at the same time.

2. One output slot per iteration

Size the output array to the iteration count and have each iteration produce exactly one element, so there is no shared destination to race over.

3. Use NativeStream for variable output

If each iteration emits a variable number of results, write them into per-index streams with NativeStream.Writer and merge afterward instead of pushing into a shared list.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Unity error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.