diff options
Diffstat (limited to 'lib/msun/src/s_log1p.c')
| -rw-r--r-- | lib/msun/src/s_log1p.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/lib/msun/src/s_log1p.c b/lib/msun/src/s_log1p.c index 4ce4c3a..0ee69a6 100644 --- a/lib/msun/src/s_log1p.c +++ b/lib/msun/src/s_log1p.c @@ -106,7 +106,7 @@ log1p(double x) ax = hx&0x7fffffff; k = 1; - if (hx < 0x3FDA827A) { /* x < 0.41422 */ + if (hx < 0x3FDA827A) { /* 1+x < sqrt(2)+ */ if(ax>=0x3ff00000) { /* x <= -1.0 */ if(x==-1.0) return -two54/zero; /* log1p(-1)=+inf */ else return (x-x)/(x-x); /* log1p(x<-1)=NaN */ @@ -118,8 +118,8 @@ log1p(double x) else return x - x*x*0.5; } - if(hx>0||hx<=((int32_t)0xbfd2bec3)) { - k=0;f=x;hu=1;} /* -0.2929<x<0.41422 */ + if(hx>0||hx<=((int32_t)0xbfd2bec4)) { + k=0;f=x;hu=1;} /* sqrt(2)/2- <= 1+x < sqrt(2)+ */ } if (hx >= 0x7ff00000) return x+x; if(k!=0) { @@ -136,7 +136,14 @@ log1p(double x) c = 0; } hu &= 0x000fffff; - if(hu<0x6a09e) { + /* + * The approximation to sqrt(2) used in thresholds is not + * critical. However, the ones used above must give less + * strict bounds than the one here so that the k==0 case is + * never reached from here, since here we have committed to + * using the correction term but don't use it if k==0. + */ + if(hu<0x6a09e) { /* u ~< sqrt(2) */ SET_HIGH_WORD(u,hu|0x3ff00000); /* normalize u */ } else { k += 1; |
