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gelufloor
mixedC++ · CPUSystems & data structuresJuly 9, 2026
the question
Is GELU's tanh approximation actually an approximation, in practice?
what came out
It depends on your precision. Its error is 7x below the bf16 rounding floor (free there) but level with the fp16 floor (not free), and it peaks in the shoulder, not the tails. A precision accounting, not a benchmark.
method & receipts
- Result: mixed
- Pre-registered — the prediction was written down and committed before the run.
→ read the code and re-run it
github.com/v-code01/gelufloor