This approximation matches the one in Eigen.

name old cpu/op new cpu/op delta BM_mlir_Log1p_f32/10 83.2ns ± 7% 34.8ns ± 5% -58.19% (p=0.000 n=84+71) BM_mlir_Log1p_f32/100 664ns ± 4% 129ns ± 4% -80.57% (p=0.000 n=82+82) BM_mlir_Log1p_f32/1k 6.75µs ± 4% 0.81µs ± 3% -88.07% (p=0.000 n=88+79) BM_mlir_Log1p_f32/10k 76.5µs ± 3% 7.8µs ± 4% -89.84% (p=0.000 n=80+80) BM_eigen_s_Log1p_f32/10 70.1ns ±14% 72.6ns ±14% +3.49% (p=0.000 n=116+112) BM_eigen_s_Log1p_f32/100 706ns ± 9% 717ns ± 3% +1.60% (p=0.018 n=117+80) BM_eigen_s_Log1p_f32/1k 8.26µs ± 1% 8.26µs ± 1% ~ (p=0.567 n=84+86) BM_eigen_s_Log1p_f32/10k 92.1µs ± 5% 92.6µs ± 6% +0.60% (p=0.047 n=115+115) BM_eigen_v_Log1p_f32/10 31.8ns ±24% 34.9ns ±17% +9.72% (p=0.000 n=98+96) BM_eigen_v_Log1p_f32/100 169ns ±10% 177ns ± 5% +4.66% (p=0.000 n=119+81) BM_eigen_v_Log1p_f32/1k 1.42µs ± 4% 1.46µs ± 8% +2.70% (p=0.000 n=93+113) BM_eigen_v_Log1p_f32/10k 14.4µs ± 5% 14.9µs ± 8% +3.61% (p=0.000 n=115+110)