I just pushed a new version of the 2^x approximation as fast_exp2() to master
and removed the old approximations. Commit
7d919e98bb116f98a6b05e56f8a05edb6825692e still has the old functions, and a
comparative benchmark.
The approximation is based on the 5th order polynomial with minimal relative
error, approximating 2^x within [-0.5...+0.5], generated with
[Sollya](http://sollya.gforge.inria.fr/). The result is almost as accurate as
the old bse_approx6_exp2(), although fast_exp() uses only float arithmetic. It
is also significantly faster than the old functions and the optimized exp2f()
variant recently added to glibc and musl
([ARM-software/exp2f](https://github.com/ARM-software/optimized-routines/blob/master/math/exp2f.c)).
~~~~
git checkout 7d919e98bb116f98a6b05e56f8a05edb6825692e && make
BSE_TEST=slow out/tests/suite1 fast_math_test fast_math_bench
RUN… fast_math_test
PASS fast_math_test
RUN… fast_math_bench
BENCH fast_exp2 # timing: fastest=0.000392s calls=458605760.0/s
diff=0.00000033028512169686 (@0.734155)
BENCH arm_exp2f # timing: fastest=0.000532s calls=338185006.7/s
diff=0.00000005979062378536 (@0.958382)
BENCH exp2f # timing: fastest=0.000650s calls=276832337.1/s
diff=0.00000005979062378536 (@0.958382)
BENCH bse_approx5_exp2 # timing: fastest=0.000768s calls=234464124.9/s
diff=0.00000458521965707170 (@0.500000)
BENCH bse_approx6_exp2 # timing: fastest=0.000847s calls=212474853.5/s
diff=0.00000022838359092781 (@0.500000)
BENCH bse_approx7_exp2 # timing: fastest=0.000854s calls=210667974.8/s
diff=0.00000000994037496760 (@0.500000)
PASS fast_math_bench
~~~~
--
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/tim-janik/beast/pull/124#issuecomment-575412715
_______________________________________________
beast mailing list
[email protected]
https://mail.gnome.org/mailman/listinfo/beast
