Regent: `__parallel_prefix` incorrect on Frontier

StanfordLegion / legion

The Legion Parallel Programming System

https://legion.stanford.edu

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Regent: `__parallel_prefix` incorrect on Frontier #1701

Open syamajala opened 2 weeks ago

syamajala commented 2 weeks ago

We're seeing S3D diverge when moving a task to gpu. The task uses __parallel_prefix and it looks the output changes. I will try to find a minimal reproducer.

syamajala commented 1 week ago

@elliottslaughter i put a reproducer for this bug on frontier here: /lustre/orion/cmb103/world-shared/seshuy/prefix

syamajala commented 3 days ago

llvm 18 and rocm 6 do not fix this error. Think its a bug in Regent.

elliottslaughter commented 3 days ago

I have reproduced this on Frontier.

CPU version: passes
HIP version: fails
CUDA version: passes

Because the CUDA version passes, this is either a bug in HIP-specific code generation or something of a mismatch when applying generic algorithms to HIP.