Barrier before reusing GQA reduction scratch - #63
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After the max reduction, reductions[0] must be read by every thread before the array is overwritten for the sum pass. Missing the barrier made causal GQA softmax nondeterministic at long sequences (antirez#52).
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Summary
threadgroup_barrierafter reading the reduced max inh3_gqa_causal_bf16before reusingreductions[]for the softmax sum.Fixes #52
Test plan
make -j && ./h3_tests