diff options
| -rw-r--r-- | lib/msun/src/s_cbrtf.c | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/lib/msun/src/s_cbrtf.c b/lib/msun/src/s_cbrtf.c index 3506943..5fcd795 100644 --- a/lib/msun/src/s_cbrtf.c +++ b/lib/msun/src/s_cbrtf.c @@ -53,16 +53,21 @@ cbrtf(float x) } else SET_FLOAT_WORD(t,sign|(hx/3+B1)); - /* first step Newton iteration (solving t*t-x/t == 0) to 16 bits */ - /* in double precision to avoid problems with denormals */ + /* + * First step Newton iteration (solving t*t-x/t == 0) to 16 bits. In + * double precision so that its terms can be arranged for efficiency + * without causing overflow or underflow. + */ T=t; r=T*T*T; - T=T*(x+x+r)/(x+r+r); + T=T*((double)x+x+r)/(x+r+r); - /* second step Newton iteration to 47 bits */ - /* in double precision for accuracy */ + /* + * Second step Newton iteration to 47 bits. In double precision for + * efficiency and accuracy. + */ r=T*T*T; - T=T*(x+x+r)/(x+r+r); + T=T*((double)x+x+r)/(x+r+r); /* rounding to 24 bits is perfect in round-to-nearest mode */ return(T); |
