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-rw-r--r--src/math/s_log1pf.c96
1 files changed, 96 insertions, 0 deletions
diff --git a/src/math/s_log1pf.c b/src/math/s_log1pf.c
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+/* s_log1pf.c -- float version of s_log1p.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#include <math.h>
+#include "math_private.h"
+
+static const float
+ln2_hi = 6.9313812256e-01, /* 0x3f317180 */
+ln2_lo = 9.0580006145e-06, /* 0x3717f7d1 */
+two25 = 3.355443200e+07, /* 0x4c000000 */
+Lp1 = 6.6666668653e-01, /* 3F2AAAAB */
+Lp2 = 4.0000000596e-01, /* 3ECCCCCD */
+Lp3 = 2.8571429849e-01, /* 3E924925 */
+Lp4 = 2.2222198546e-01, /* 3E638E29 */
+Lp5 = 1.8183572590e-01, /* 3E3A3325 */
+Lp6 = 1.5313838422e-01, /* 3E1CD04F */
+Lp7 = 1.4798198640e-01; /* 3E178897 */
+
+static const float zero = 0.0;
+
+float
+log1pf(float x)
+{
+ float hfsq,f=0,c=0,s,z,R,u;
+ int32_t k,hx,hu=0,ax;
+
+ GET_FLOAT_WORD(hx,x);
+ ax = hx&0x7fffffff;
+
+ k = 1;
+ if (hx < 0x3ed413d7) { /* x < 0.41422 */
+ if(ax>=0x3f800000) { /* x <= -1.0 */
+ if(x==(float)-1.0) return -two25/zero; /* log1p(-1)=+inf */
+ else return (x-x)/(x-x); /* log1p(x<-1)=NaN */
+ }
+ if(ax<0x31000000) { /* |x| < 2**-29 */
+ if(two25+x>zero /* raise inexact */
+ &&ax<0x24800000) /* |x| < 2**-54 */
+ return x;
+ else
+ return x - x*x*(float)0.5;
+ }
+ if(hx>0||hx<=((int32_t)0xbe95f61f)) {
+ k=0;f=x;hu=1;} /* -0.2929<x<0.41422 */
+ }
+ if (hx >= 0x7f800000) return x+x;
+ if(k!=0) {
+ if(hx<0x5a000000) {
+ u = (float)1.0+x;
+ GET_FLOAT_WORD(hu,u);
+ k = (hu>>23)-127;
+ /* correction term */
+ c = (k>0)? (float)1.0-(u-x):x-(u-(float)1.0);
+ c /= u;
+ } else {
+ u = x;
+ GET_FLOAT_WORD(hu,u);
+ k = (hu>>23)-127;
+ c = 0;
+ }
+ hu &= 0x007fffff;
+ if(hu<0x3504f7) {
+ SET_FLOAT_WORD(u,hu|0x3f800000);/* normalize u */
+ } else {
+ k += 1;
+ SET_FLOAT_WORD(u,hu|0x3f000000); /* normalize u/2 */
+ hu = (0x00800000-hu)>>2;
+ }
+ f = u-(float)1.0;
+ }
+ hfsq=(float)0.5*f*f;
+ if(hu==0) { /* |f| < 2**-20 */
+ if(f==zero) { if(k==0) return zero;
+ else {c += k*ln2_lo; return k*ln2_hi+c;} }
+ R = hfsq*((float)1.0-(float)0.66666666666666666*f);
+ if(k==0) return f-R; else
+ return k*ln2_hi-((R-(k*ln2_lo+c))-f);
+ }
+ s = f/((float)2.0+f);
+ z = s*s;
+ R = z*(Lp1+z*(Lp2+z*(Lp3+z*(Lp4+z*(Lp5+z*(Lp6+z*Lp7))))));
+ if(k==0) return f-(hfsq-s*(hfsq+R)); else
+ return k*ln2_hi-((hfsq-(s*(hfsq+R)+(k*ln2_lo+c)))-f);
+}