This approximation matches the one in Eigen.

name old cpu/op new cpu/op delta BM_mlir_Expm1_f32/10 90.9ns ± 4% 52.2ns ± 4% -42.60% (p=0.000 n=74+87) BM_mlir_Expm1_f32/100 837ns ± 3% 231ns ± 4% -72.43% (p=0.000 n=79+69) BM_mlir_Expm1_f32/1k 8.43µs ± 3% 1.58µs ± 5% -81.30% (p=0.000 n=77+83) BM_mlir_Expm1_f32/10k 83.8µs ± 3% 15.4µs ± 5% -81.65% (p=0.000 n=83+69) BM_eigen_s_Expm1_f32/10 68.8ns ±17% 72.5ns ±14% +5.40% (p=0.000 n=118+115) BM_eigen_s_Expm1_f32/100 694ns ±11% 717ns ± 2% +3.34% (p=0.000 n=120+75) BM_eigen_s_Expm1_f32/1k 7.69µs ± 2% 7.97µs ±11% +3.56% (p=0.000 n=95+117) BM_eigen_s_Expm1_f32/10k 88.0µs ± 1% 89.3µs ± 6% +1.45% (p=0.000 n=74+106) BM_eigen_v_Expm1_f32/10 44.3ns ± 6% 45.0ns ± 8% +1.45% (p=0.018 n=81+111) BM_eigen_v_Expm1_f32/100 351ns ± 1% 360ns ± 9% +2.58% (p=0.000 n=73+99) BM_eigen_v_Expm1_f32/1k 3.31µs ± 1% 3.42µs ± 9% +3.37% (p=0.000 n=71+100) BM_eigen_v_Expm1_f32/10k 33.7µs ± 8% 34.1µs ± 9% +1.04% (p=0.007 n=99+98)