From 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 12 Feb 2011 00:22:29 -0500
Subject: initial check-in, version 0.5.0

---
 src/math/s_log1pf.c | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 src/math/s_log1pf.c

(limited to 'src/math/s_log1pf.c')

diff --git a/src/math/s_log1pf.c b/src/math/s_log1pf.c
new file mode 100644
index 00000000..dcdd6bb3
--- /dev/null
+++ b/src/math/s_log1pf.c
@@ -0,0 +1,96 @@
+/* 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);
+}
-- 
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